Co-reporter:Chandan L. Barhate, Erik L. Regalado, Nathan D. Contrella, Joon Lee, Junyong Jo, Alexey A. Makarov, Daniel W. Armstrong, and Christopher J. Welch
Analytical Chemistry March 21, 2017 Volume 89(Issue 6) pp:3545-3545
Publication Date(Web):January 11, 2017
DOI:10.1021/acs.analchem.6b04834
Chromatographic separation and analysis of complex mixtures of closely related species is one of the most challenging tasks in modern pharmaceutical analysis. In recent years, two-dimensional liquid chromatography (2D-LC) has become a valuable tool for improving peak capacity and selectivity. However, the relatively slow speed of chiral separations has limited the use of chiral stationary phases (CSPs) as the second dimension in 2D-LC, especially in the comprehensive mode. Realizing that the recent revolution in the field of ultrafast enantioselective chromatography could now provide significantly faster separations, we herein report an investigation into the use of ultrafast chiral chromatography as a second dimension for 2D chromatographic separations. In this study, excellent selectivity, peak shape, and repeatability were achieved by combining achiral and chiral narrow-bore columns (2.1 mm × 100 mm and 2.1 mm × 150 mm, sub-2 and 3 μm) in the first dimension with 4.6 mm × 30 mm and 4.6 mm × 50 mm columns packed with highly efficient chiral selectors (sub-2 μm fully porous and 2.7 μm fused-core particles) in the second dimension, together with the use of 0.1% phosphoric acid/acetonitrile eluents in both dimensions. Multiple achiral × chiral and chiral × chiral 2D-LC examples (single and multiple heart-cutting, high-resolution sampling, and comprehensive) using ultrafast chiral chromatography in the second dimension are successfully applied to the separation and analysis of complex mixtures of closely related pharmaceuticals and synthetic intermediates, including chiral and achiral drugs and metabolites, constitutional isomers, stereoisomers, and organohalogenated species.
Co-reporter:Christopher J. Welch, Margaret M. Faul, Srinivas Tummala, Charles D. Papageorgiou, Frederick Hicks, Joel M. Hawkins, Nicholas Thomson, Aaron Cote, Shailendra Bordawekar, Steven J. Wittenberger, David Laffan, Mark Purdie, Pierre Boulas, Erwin Irdam, Keith Horspool, Bing-Shiou Yang, Jean Tom, Paul Fernandez, Antonio Ferretti, Scott May, Kevin Seibert, Kenneth Wells, and Rahn McKeown
Organic Process Research & Development March 17, 2017 Volume 21(Issue 3) pp:414-414
Publication Date(Web):February 3, 2017
DOI:10.1021/acs.oprd.6b00427
The creation of the Enabling Technologies Consortium (ETC) is described. The ETC fosters precompetitive collaborations aimed at the development and evaluation of new enabling technologies for pharmaceutical research and development, with an initial focus on chemistry, manufacturing, and controls. An overview of the structure and function of the new organization, which will carry out its work while remaining mindful of antitrust compliance requirements, is herein presented along with a description of several ongoing development projects.
Co-reporter:Chandan L. Barhate;Leo A. Joyce;Alexey A. Makarov;Kerstin Zawatzky;Frank Bernardoni;Wes A. Schafer;Daniel W. Armstrong;Erik L. Regalado
Chemical Communications 2017 vol. 53(Issue 3) pp:509-512
Publication Date(Web):2017/01/03
DOI:10.1039/C6CC08512A
Recent developments in fast chromatographic enantioseparations now make high throughput analysis of enantiopurity on the order of a few seconds achievable. Nevertheless, routine chromatographic determinations of enantiopurity to support stereochemical investigations in pharmaceutical research and development, synthetic chemistry and bioanalysis are still typically performed on the 5–20 min timescale, with many practitioners believing that sub-minute enantioseparations are not representative of the molecules encountered in day to day research. In this study we develop ultrafast chromatographic enantioseparations for a variety of pharmaceutically-related drugs and intermediates, showing that sub-minute resolutions are now possible in the vast majority of cases by both supercritical fluid chromatography (SFC) and reversed phase liquid chromatography (RP-LC). Examples are provided illustrating how such methods can be routinely developed and used for ultrafast high throughput analysis to support enantioselective synthesis investigations.
Co-reporter:Christopher J. Welch;Kerstin Zawatzky;Alexey A. Makarov;Satoshi Fujiwara;Arimasa Matsumoto;Kenso Soai
Organic & Biomolecular Chemistry 2017 vol. 15(Issue 1) pp:96-101
Publication Date(Web):2016/12/20
DOI:10.1039/C6OB01939K
An investigation is reported on the use of the autocatalytic enantioselective Soai reaction, known to be influenced by the presence of a wide variety of chiral materials, as a generic tool for measuring the enantiopurity and absolute configuration of any substance. Good generality for the reaction across a small group of test analytes was observed, consistent with literature reports suggesting a diversity of compound types that can influence the stereochemical outcome of this reaction. Some trends in the absolute sense of stereochemical enrichment were noted, suggesting the possible utility of the approach for assigning absolute configuration to unknown compounds, by analogy to closely related species with known outcomes. Considerable variation was observed in the triggering strength of different enantiopure materials, an undesirable characteristic when dealing with mixtures containing minor impurities with strong triggering strength in the presence of major components with weak triggering strength. A strong tendency of the reaction toward an ‘all or none’ type of behavior makes the reaction most sensitive for detecting enantioenrichment close to zero. Consequently, the ability to discern modest from excellent enantioselectivity was relatively poor. While these properties limit the ability to obtain precise enantiopurity measurements in a simple single addition experiment, prospects may exist for more complex experimental setups that may potentially offer improved performance.
Co-reporter:Kerstin Zawatzky, Chandan L. Barhate, Erik L. Regalado, Benjamin F. Mann, Nicholas Marshall, Jeffrey C. Moore, Christopher J. Welch
Journal of Chromatography A 2017 Volume 1499(Volume 1499) pp:
Publication Date(Web):26 May 2017
DOI:10.1016/j.chroma.2017.04.002
•Increase of throughput in chromatographic analysis by high speed autosampler technology.•Combination with ultrafast chromatographic separation enables analysis of 96 well plates in 17 min.•Demonstrated for high speed enantiopurity analysis as well as rapid analysis for biocatalyst screening.The combination of high speed autosampler technology and ultrafast chromatographic separations enables faster high throughput analysis. With an injection cycle time of 10.6 s, MISER (Multiple Injection in a Single Experimental Run) HPLC–MS analysis of a 96 well microplate can be completed in only 17 min. As chromatographic separations in the sub 5 s range become increasingly common, even faster autosamplers will be needed to realize further speed improvements in high throughput LC–MS analysis. Indeed with proper hardware sampling approaches, chromatographic analysis of microplates could approach speeds of spectrophotometric plate readers while maintaining the advantage of multicomponent detection and monitoring.
Co-reporter:Xiaodong Bu;Michael Williams;Junyong Jo;Kazunori Koide
Chemical Communications 2017 vol. 53(Issue 4) pp:720-723
Publication Date(Web):2017/01/05
DOI:10.1039/C6CC08562H
Rapid palladium (Pd) catalyzed deallylation of an uncoloured reagent within a flowing stream affords a dose dependent colour formation that can be used for convenient online analysis of trace levels of Pd contamination using a modified HPLC instrument. An application to the online sensing of Pd breakthrough from a flow through Pd adsorption cartridge is described. An alternative configuration of the instrumentation allows the rapid (<1 min) and accurate measurement of Pd levels within samples injected via a conventional HPLC autosampler.
Co-reporter:Kerstin Zawatzky, Mirlinda Biba, Erik L. Regalado, Christopher J. Welch
Journal of Chromatography A 2016 Volume 1429() pp:374-379
Publication Date(Web):15 January 2016
DOI:10.1016/j.chroma.2015.12.057
•Use of MISER (Multiple Injections in a Single Experimental Run) in supercritical fluid chromatography.•Ultrafast separations combined with fast autosampler injection times allow analysis of a 96 well plate in about 33 min.•User-friendly method for injector programming is shown for two recent SFC instruments.MISER chromatographic analysis (Multiple Injections in a Single Experimental Run) using supercritical fluid chromatography (SFC) with pressurized carbon dioxide-based eluents is well suited to the high throughput analysis of enantiopurity. SFC is currently the preferred method for fast enantiopurity analysis, with analysis times of only a few seconds achievable in some cases. Injector programming using both the Agilent Infinity and Shimadzu Nexera UC instruments permitted MISER SFC experiments to be performed. Several case studies are presented, showcasing the power and versatility of the technique, with ‘plate analysis times’ (the time required for analysis of enantiopurity of 96 samples) of less than 33–34 min achievable in the best cases.
Co-reporter:Robert Sheridan, Wes Schafer, Patrick Piras, Kerstin Zawatzky, Edward C. Sherer, Christian Roussel, Christopher J. Welch
Journal of Chromatography A 2016 Volume 1467() pp:206-213
Publication Date(Web):7 October 2016
DOI:10.1016/j.chroma.2016.05.066
•Data mining the Chirbase database of >200,000 reported chromatographic enantiomer separations affords QSAR models for the prediction of which chiral stationary phase will work for a given compound.•QSAR models for only 4 CSPs afforded good predictivity: DNB-Leu, Crownpak, Whelk-O, Chirobiotic T.•Fair to good predictivity for successful separations was obtained.•Excellent predicitivity for unsuccessful separations was obtained.•More comprehensive inclusion of ‘negative results’ for separations that work poorly or not at all may be helpful in obtaining improved QSAR models for CSP selection.•Precompetitive collaboration may be helpful in data sharing for generation of improved QSAR models for CSP selection.ChirBase, a database for the chromatographic separation of enantiomers containing more than 200,000 records compiled from the literature, was used to develop quantitative structure activity models for the prediction of which chiral stationary phase will work for the separation of a given molecule. Constructuion of QSAR models for the enantioseparation of nineteen chiral stationary phases was attempted using only analyte structural information, leading to the producton of self-consistent models in four cases. These models were tested by predicting which in-house racemic compounds would and would not be resolved on the different columns. Some degree of success was observed, but the sparseness of data within ChirBase, which contains enantioseparations for only a subset of molecules on a subset of columns under a variety of conditions may limit the creation of effective models. Augmented data sets gleaned from automated chromatographic method development systems deployed in academic and industrial research laboratories or the use of models that take other factors such as solvent composition, temperature, etc. into account could potentially be useful for the development of more robust models.
Co-reporter:Kerstin Zawatzky, Mikhail Reibarkh, Nicole Canfield, Ting-Chuan Wang, Shanren Li, Liangcheng Du, Christopher J. Welch
Journal of Chromatography A 2016 Volume 1468() pp:245-249
Publication Date(Web):14 October 2016
DOI:10.1016/j.chroma.2016.09.025
•Subtraction of chromatograms used to visualize small differences.•Algorithms that perform peak alignment and interpolation improve results remarkably.•In combination with multiple injections analysis it can be a simple tool to facilitate data analysis by visual interpretation in high throughput analysis.Subtraction of chromatograms coming from two different samples collected under identical conditions can highlight small variations, serving as a useful tool for visualizing differences between experimental and control groups. While the basis for this general approach has been known for decades, the technique is seldom used in modern chromatographic analysis. We report an investigation into the application of subtractive chromatographic analysis in several areas of pharmaceutical research where detection of small differences between samples is important. Our investigation found that elimination of artifacts caused by peak misalignment was often necessary, especially for extremely sharp chromatographic peaks obtained in rapid injection MISER chromatography. Alignment of individual peaks prior to subtraction, combined with fast detector sampling rates, or data interpolation in cases where this is not possible, was found to afford convenient visualization of small differences (∼1%) among samples, suggesting potential utility in high throughput screening of process adsorbents or other applications in pharmaceutical research and development.
Co-reporter:Kerstin Zawatzky, Mingxiang Lin, Wes Schafer, Bing Mao, Oliver Trapp, Christopher J. Welch
Journal of Chromatography A 2016 Volume 1465() pp:205-210
Publication Date(Web):23 September 2016
DOI:10.1016/j.chroma.2016.08.047
•Chromatogram averaging used to improve signal to noise ratio.•Quantitation of trace level impurities below limit of detection can be achieved without need to change existing analysis method.•Hadamard encoded multiplexing was applied to save time and improve signal to noise ratio in analysis of potential mutagenic impurities in pharmaceutical analysis.Averaging of chromatograms can lead to enhancement of signal to noise ratio (S/N) in proportion to the square root of the number of measurements. Although the general principle has been known for decades, chromatogram averaging is almost never used in current pharmaceutical research. In this study we explore the utility of this approach, showing it to be a simple and easily accessible method for boosting sensitivity for quantification of minor components and trace impurities, where current techniques deliver insufficient S/N.
Co-reporter:Keith W. Bentley, Leo A. Joyce, Edward C. Sherer, Huaming Sheng, Christian Wolf, and Christopher J. Welch
The Journal of Organic Chemistry 2016 Volume 81(Issue 3) pp:1185-1191
Publication Date(Web):January 12, 2016
DOI:10.1021/acs.joc.5b02716
Molecular hosts capable of chiroptical sensing of complexed guest molecules offer an attractive alternative to conventional methods for the analysis of the absolute configuration and enantiopurity. Sensors based on the Pfeiffer effect rely on complexation-driven asymmetric transformation of the first kind and can produce a chiroptical signal against an otherwise null background. To be most effective, the wavelength of the induced chiroptical sensor readout should be free and clear of interfering signals coming from the sample under investigation. In this study, we report the introduction of stereodynamic zinc complexes of antenna biphenols, a new class of sensors bearing antenna-like appendages that can extend the wavelength of the chiroptical signal while also improving enantioselective guest recognition.
Co-reporter:Lu Yang, Thomas Wenzel, R. Thomas Williamson, Melodie Christensen, Wes Schafer, and Christopher J. Welch
ACS Central Science 2016 Volume 2(Issue 5) pp:332
Publication Date(Web):April 20, 2016
DOI:10.1021/acscentsci.6b00062
The use of NMR chiral solvating agents (CSAs) for the analysis of enantiopurity has been known for decades, but has been supplanted in recent years by chromatographic enantioseparation technology. While chromatographic methods for the analysis of enantiopurity are now commonplace and easy to implement, there are still individual compounds and entire classes of analytes where enantioseparation can prove extremely difficult, notably, compounds that are chiral by virtue of very subtle differences such as isotopic substitution or small differences in alkyl chain length. NMR analysis using CSAs can often be useful for such problems, but the traditional approach to selection of an appropriate CSA and the development of an NMR-based analysis method often involves a trial-and-error approach that can be relatively slow and tedious. In this study we describe a high-throughput experimentation approach to the selection of NMR CSAs that employs automation-enabled screening of prepared libraries of CSAs in a systematic fashion. This approach affords excellent results for a standard set of enantioenriched compounds, providing a valuable comparative data set for the effectiveness of CSAs for different classes of compounds. In addition, the technique has been successfully applied to challenging pharmaceutical development problems that are not amenable to chromatographic solutions. Overall, this methodology provides a rapid and powerful approach for investigating enantiopurity that compliments and augments conventional chromatographic approaches.
Co-reporter:Xiaodong Bu, Erik L. Regalado, Simon E. Hamilton, Christopher J. Welch
TrAC Trends in Analytical Chemistry 2016 Volume 82() pp:22-34
Publication Date(Web):September 2016
DOI:10.1016/j.trac.2016.04.025
•New trends in low-cost compact MS chromatographic detectors for chemical analysis.•Recent developments in LC-MS methods using compact MS detectors.•Compact MS instruments at half the cost of conventional spectrometers provide excellent detection sensitivity.•Use of Microsaic 3500 MiD, Advion Compact and Acquity QDa MS detectors across academia and industries.•Use of LC-mini MS for reaction monitoring, biomolecule / high-throughput microplate / impurities / degradation products / trace / PMIs analyzes.An overview of recent progress in the development of compact mass spectrometers for use as chromatographic detectors in chemical analysis is presented. As the applications of LC-MS technologies have grown in recent years there has been a continued expansion of the approach to new user groups. Within the pharmaceutical industry, the recent development of small, inexpensive and quiet MS detectors for LC has enabled the rollout of this important technology well beyond the initial user base of researchers in drug metabolism and bioanalysis to the direct support of research areas such as discovery chemistry, process chemistry, chemical engineering, manufacturing and formulation sciences, with comparable broadening of the MS user base occurring in other industries and in academia. In this review we survey recent developments and applications ranging from reaction monitoring, biomolecule analysis and high-throughput microplate analysis to the identification and analysis of impurities, degradation products and potential mutagens, offering thoughts on current limitations and future directions.
Co-reporter:Christopher J. Welch, Timothy Nowak, Leo A. Joyce, and Erik L. Regalado
ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 9) pp:1897
Publication Date(Web):August 13, 2015
DOI:10.1021/acssuschemeng.5b00728
Co-reporter:Christopher J. Welch, Timothy Nowak, Leo A. Joyce, and Erik L. Regalado
ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 5) pp:1000
Publication Date(Web):April 2, 2015
DOI:10.1021/acssuschemeng.5b00133
HPLC and HPLC-MS are powerful and wide ranging analytical tools employed in every aspect of modern chemical and biomedical research. The use of these tools is currently restricted to formal laboratory environments, partly due to cost and complexity but also owing to the special handling requirements for the solvents consumed and waste generated by these instruments. Ongoing innovations targeting the decrease in cost, size, and complexity of HPLC and HPLC-MS instrumentation raise the intriguing possibility that such tools may soon become both mobile and widespread in usage, breaking free of traditional laboratory boundaries. However, the dependence of these techniques on regulated organic solvents currently limits such mobility. In this study, we investigate the use of distilled alcohol spirits (cachaça, rum, vodka, aguardiente, etc.) as well as other household items typically available in a supermarket (vinegar, ammonia) as mobile phases and additives for carrying out HPLC and HPLC-MS experiments, showing that in many cases excellent analytical performance can be obtained using these low cost, universally available, green alternatives to the organic solvents typically used in such studies.Keywords: Ethanol-based mobile phases; Food chemistry; Green chromatography; High performance liquid chromatography; Microfluidic chromatography;
Co-reporter:Erik L. Regalado
Journal of Separation Science 2015 Volume 38( Issue 16) pp:2826-2832
Publication Date(Web):
DOI:10.1002/jssc.201500270
Chromatographic enantioseparations on the order of a few seconds can be achieved by supercritical fluid chromatography using short columns packed with chiral stationary phases. The evolution of ‘world record’ speeds for the chromatographic separation of enantiomers has steadily dropped from an industry standard of 20–40 min just two decades ago, to a current ability to perform many enantioseparations in well under a minute. Improvements in instrument and column technologies enabled this revolution, but the ability to predict optimal separation time from an initial method development screening assay using the tmin cc predictor greatly simplifies the development and optimization of high-speed chiral chromatographic separations. In this study, we illustrate how the use of this simple tool in combination with the workhorse technique of supercritical fluid chromatography on customized short chiral columns (1–2 cm length) allows us to achieve ultrafast enantioseparations of pharmaceutically relevant compounds on the 5–20 s scale, bringing the technique of high-throughput enantiopurity analysis out of the specialist realm and into the laboratories of most researchers.
Co-reporter:Erik L. Regalado, Alexey A. Makarov, Ray McClain, Matthew Przybyciel, Christopher J. Welch
Journal of Chromatography A 2015 1380() pp: 45-54
Publication Date(Web):
DOI:10.1016/j.chroma.2014.12.025
Co-reporter:Erik L. Regalado, Christopher J. Welch
TrAC Trends in Analytical Chemistry 2015 Volume 67() pp:74-81
Publication Date(Web):April 2015
DOI:10.1016/j.trac.2015.01.004
•Solving multicomponent achiral separation challenges via SFC with chiral stationary phases (CSPs).•Challenging mixtures of achiral drug metabolites and analogs can often be resolved by CSPs in SFC mode.•Achiral UHPLC and SFC vs chiral SFC for separation of closely related achiral analytes.•Separation of complex non-enantiomeric mixtures often require alternative approaches such as chiral SFC.In recent years, chiral supercritical fluid chromatography (SFC) has emerged as the preferred technique for analytical, semi-preparative and preparative separation of enantiomers in the pharmaceutical industry, due to advantages in speed, high column efficiency and significantly lower mobile-phase consumption than conventional liquid chromatography (LC) techniques. We illustrate the benefits of SFC using chiral stationary phases (CSPs) in method development for separating multicomponent mixtures of closely-related achiral analytes, including hydroxylation isomers, halogen-containing molecules, drug metabolites and analogs, methylation and demethylation species, constitutional isomers, and diastereomers. We present several case studies to illustrate the advantage of using SFC with CSPs for achiral separations, where conventional achiral LC and achiral SFC methods fail or deliver sub-optimal chromatographic performance.
Co-reporter:Erik L. Regalado, Ping Zhuang, Yadan Chen, Alexey A. Makarov, Wes A. Schafer, Neil McGachy, and Christopher J. Welch
Analytical Chemistry 2014 Volume 86(Issue 1) pp:805
Publication Date(Web):December 10, 2013
DOI:10.1021/ac403376h
In recent years, the use of halogen-containing molecules has proliferated in the pharmaceutical industry, where the incorporation of halogens, especially fluorine, has become vitally important for blocking metabolism and enhancing the biological activity of pharmaceuticals. The chromatographic separation of halogen-containing pharmaceuticals from associated isomers or dehalogenation impurities can sometimes be quite difficult. In an attempt to identify the best current tools available for addressing this important problem, a survey of the suitability of four chromatographic method development platforms (ultra high-performance liquid chromatography (UHPLC), core shell HPLC, achiral supercritical fluid chromatography (SFC) and chiral SFC) for separating closely related mixtures of halogen-containing pharmaceuticals and their dehalogenated isosteres is described. Of the 132 column and mobile phase combinations examined for each mixture, a small subset of conditions were found to afford the best overall performance, with a single UHPLC method (2.1 × 50 mm, 1.9 μm Hypersil Gold PFP, acetonitrile/methanol based aqueous eluents containing either phosphoric or perchloric acid with 150 mM sodium perchlorate) affording excellent separation for all samples. Similarly, a survey of several families of closely related halogen-containing small molecules representing the diversity of impurities that can sometimes be found in purchased starting materials for synthesis revealed chiral SFC (Chiralcel OJ-3 and Chiralpak IB, isopropanol or ethanol with 25 mM isobutylamine/carbon dioxide) as well as the UHPLC (2.1 × 50 mm, 1.8 μm ZORBAX RRHD Eclipse Plus C18 and the Gold PFP, acetonitrile/methanol based aqueous eluents containing phosphoric acid) as preferred methods.
Co-reporter:Erik L. Regalado, Marisa C. Kozlowski, John M. Curto, Tobias Ritter, Michael G. Campbell, Anthony R. Mazzotti, Bruce C. Hamper, Christopher D. Spilling, Michael P. Mannino, Li Wan, Jin-Quan Yu, Jinchu Liu and Christopher J. Welch
Organic & Biomolecular Chemistry 2014 vol. 12(Issue 14) pp:2161-2166
Publication Date(Web):20 Feb 2014
DOI:10.1039/C3OB42195C
The use of state-of-the-art separation tools from the pharmaceutical industry for addressing intractable separation problems from academic synthetic chemistry is evaluated, showing fast and useful results for the resolution of complex mixtures, separation of closely related components, visualization of difficult to detect compounds and purification of synthetic intermediates. Some recommendations for potential near term deployment of separation tools within academia and the evolution of next generation separation technologies are discussed.
Co-reporter:Erik L. Regalado, Joseph A. Schariter, Christopher J. Welch
Journal of Chromatography A 2014 Volume 1363() pp:200-206
Publication Date(Web):10 October 2014
DOI:10.1016/j.chroma.2014.08.025
•Several offline and online 2D RPLC methods to separate a multicomponent mixture were developed.•A standard mixture of 12 warfarins and monohydroxylated isomers were resolved in 16.2 min.•Online two-dimensional LC method by chiral RP-HPLC × achiral RP-UHPLC provided the fastest separation of all isomers.Several offline and online 2D HPLC methods were investigated for the reversed phase resolution of a complex mixture of closely related warfarin and hydroxywarfarin isomers. By combining reversed phase achiral/chiral HPLC separation with UV-triggered fraction collection and subsequent chiral/achiral reversed phase HPLC analysis of collected fractions, complete resolution of all 12 components of the mixture was possible. In addition, a faster method was developed from online 2D HPLC analysis where multicomponent fractions from the first dimension are simultaneously chromatographed in the second dimension.
Co-reporter:Erik L. Regalado;Roy Helmy;Mitchell D. Green
Journal of Separation Science 2014 Volume 37( Issue 9-10) pp:1094-1102
Publication Date(Web):
DOI:10.1002/jssc.201400038
In this study, we investigate the separation of a variety of mixtures of drugs, metabolites, and related analogs including representatives of the carbamazepine, methylated xanthine, steroid hormone, nicotine, and morphine families using several automated chromatographic method development screening systems including ultra high performance liquid chromatography, core–shell HPLC, achiral supercritical fluid chromatography (SFC), and chiral SFC. Of the 138 column and mobile phase combinations examined for each mixture, a few chromatographic conditions afford the best overall performance, with a single achiral SFC method (4.6 × 250 mm, 3.0 μm GreenSep Ethyl Pyridine, 25 mM isobutylamine in methanol/CO2) affording good separation for all samples. Four of these mixtures were also resolved by achiral SFC on the Luna HILIC and chiral SFC Chiralpak IB columns using methanol or ethanol with 25 mM isobutylamine as polar modifiers. Modifications of standard chromatography screening conditions afforded fast separation methods (from 1 to 5 min) for baseline resolution of all components of each of these challenging sets of closely related compounds.
Co-reporter:Erik L. Regalado, Renee K. Dermenjian, Leo A. Joyce, Christopher J. Welch
Journal of Pharmaceutical and Biomedical Analysis 2014 Volume 92() pp:1-5
Publication Date(Web):15 April 2014
DOI:10.1016/j.jpba.2013.12.043
•UHPLC–DAD–HRESIMS method for detection of dehalogenation impurities in pharmaceuticals.•Resolution and MS compatible detection with a perflurophenyl column and ACN/NH4HCO2 (pH 3.5) eluent.•Lower resolution single quadrupole MS detector correctly identified potential dehalogenation impurities.•Unambiguous identification of dehalogenation impurities or associated isomers by HRESI(+) detection.The presence of dehalogenated impurities is often observed in halogen-containing pharmaceuticals, and can present a difficult analytical challenge, as the chromatographic behavior of the halogenated drug and the hydrogen-containing analog can be quite similar. In this study we describe the chromatographic separation and unambiguous identification of dehalogenation impurities or associated isomers in organohalogenated pharmaceuticals using UHPLC with a pentafluorophenyl column coupled with diode-array and high resolution electrospray ionization mass spectrometry detection (UHPLC–DAD–HRESIMS).
Co-reporter:Xiaodong Bu, Jiong Yang, Xiaoyi Gong, Christopher J. Welch
Journal of Pharmaceutical and Biomedical Analysis 2014 Volume 94() pp:139-144
Publication Date(Web):June 2014
DOI:10.1016/j.jpba.2014.01.029
•Small, inexpensive MS instruments with reduced capabilities as routine tools.•Evaluation of a compact mass spectrometer for supporting pharmaceutical chemistry.•Applications such as product and impurity identification, and reaction monitoring.•Study of PGIs assessment and high molecular weight biomolecules.•Achieved sub-nanogram limit of detection and impurity identification below 0.1%.The suitability of a recently introduced inexpensive, compact mass spectrometer detector is evaluated for supporting pharmaceutical chemistry investigations. While high performance/high cost MS detectors dominate the marketplace, there is growing recognition of the need for a small, inexpensive MS detector with reduced capabilities for supporting synthetic chemistry investigations, where reduced sensitivity and unit mass resolution are often suitable for solving routine problems. In this study, the fundamental performance characteristics of the recently introduced Advion compact mass spectrometer were evaluated, investigating the use of the instrument for routine product and impurity identification, reaction monitoring, evaluation of potential genotoxic impurities and study of high molecular weight biomolecules. In general, the results of the evaluation show this compact and inexpensive mass spectrometer to be well suited for providing reliable support for pharmaceutical chemistry investigations, with sub-nanogram limit of detection and impurity identification below 0.1% being possible in some instance.
Co-reporter:Simon E. Hamilton, Fred Mattrey, Xiaodong Bu, David Murray, Bryan McCullough, and Christopher J. Welch
Organic Process Research & Development 2014 Volume 18(Issue 1) pp:103-108
Publication Date(Web):December 3, 2013
DOI:10.1021/op400253x
In this study we describe the evaluation of a recently developed miniaturized single-quadrupole mass spectrometer to support pharmaceutical process research investigations. Mass spectrometry is becoming an indispensable tool for analytical support of synthetic chemistry; however, current mass spectrometers are too expensive and too large for widespread deployment. In addition, current instruments often have features and capabilities that, while useful for trace component or bioanalysis applications, are beyond the comparatively simple requirements of synthetic chemists, where samples are often abundant and unit mass resolution is generally sufficient. An evaluation of the Microsaic 3500 MiD shows this small and inexpensive mass spectrometer to be well-suited for providing reliable support for certain pharmaceutical process research investigations.
Co-reporter:Christopher J. Welch, Joel M. Hawkins, and Jean Tom
Organic Process Research & Development 2014 Volume 18(Issue 4) pp:481-487
Publication Date(Web):March 7, 2014
DOI:10.1021/op500023q
As the pharmaceutical industry continues to explore new ways to stimulate innovation, reduce costs, and streamline operations, the idea of joining forces in cross-pharma collaborations on the development of new and valuable precompetitive technologies becomes increasingly attractive. Before industry-wide precompetitive collaboration can become truly commonplace and more effective, improved approaches for creating and maintaining collaborations between competitors are needed. A recent Council for Chemical Research workshop at the University of Pennsylvania on precompetitive collaborations on enabling chemical and chemical engineering technologies for the pharmaceutical industry revealed widespread interest among participants from industry, academia and government to augment and improve current methods. While it is important not to underestimate the challenges of multiparty collaborations, the value coming from pooling resources and combining intellectual input provides strong incentive to improve and foster precompetitive collaborations. Here we summarize key points from this discussion and propose a new hybrid model for improved collaborative development of new enabling technologies for the pharmaceutical industry.
Co-reporter:Christopher J. Welch, Erik L. Regalado, E. Celeste Welch, Isaac M. K. Eckert and Christina Kraml
Analytical Methods 2014 vol. 6(Issue 3) pp:857-862
Publication Date(Web):10 Dec 2013
DOI:10.1039/C3AY41953C
The advantages of MISER LC-MS (high throughput, simple readout of results) are demonstrated in the analysis of E-capsaicin in chili peppers and hot sauces. The ready availability of samples with a wide range of capsaicin content and the fast and easy detection using the MISER (Multiple Injections in a Single Experimental Run) technique makes this a potentially useful experiment to introduce novices to the important analytical technique of LC-MS. In this study we describe a simple and rapid chromatographic method for evaluation of E-capsaicin in chili peppers using HPLC with 80% organic eluent in a Poroshell SB-C18 column coupled with electrospray ionization mass spectrometry detection and MISER analysis. The misergrams obtained from continuous sample injections every 0.73 min allow the convenient simultaneous visualization of the outcomes of multiple experiments represented as single chromatograms. A considerable variation in E-capsaicin levels is clearly visualized among different types of peppers and sauces, with the ghost pepper (Bhut Jolokia) showing the highest E-capsaicin concentration of the peppers sampled.
Co-reporter:Erik L. Regalado;Edward C. Sherer;Mitchell D. Green;Derek W. Hendersonl;R. Thomas Williamson;Leo A. Joyce
Chirality 2014 Volume 26( Issue 2) pp:95-101
Publication Date(Web):
DOI:10.1002/chir.22274
ABSTRACT
The absolute configuration of several hydroxywarfarin isomers was assigned using a comparison of elution order on chiral stationary phases, optical rotation, and circular dichroism (CD) spectra, with confirmation of assignments made by comparison between experimental and calculated CD spectra and selective synthesis of hydroxywarfarin isomers from enantiopure warfarin using human liver microsomes. Chirality 26:95–101, 2014. © 2013 Wiley Periodicals, Inc.
Co-reporter:Erik L. Regalado, Wes Schafer, Ray McClain, Christopher J. Welch
Journal of Chromatography A 2013 Volume 1314() pp:266-275
Publication Date(Web):1 November 2013
DOI:10.1016/j.chroma.2013.07.092
•Rapid chiral and achiral screening platforms for separation and analysis of complex mixtures.•1.8 min achiral SFC method for separation of warfarin and hydroxylated isomers.•8.0 min chiral SFC method for resolution of all twelve components.•2.6 min achiral RP-UPLC method for separation of warfarin and hydroxywarfarins.•RP chiral LC–MS method using MS deconvolution for enantioseparation of hydroxywarfarins.Recent developments in the field of organic synthesis are leading to increasingly complex mixtures of closely related species (positional isomers, regioisomers, diastereomers, etc.) that often prove challenging for chromatographic analysis and separation. In this study we investigate the separation of a representative mixture of warfarin and 5 different monohydroxylation isomers to assess whether conventional techniques are suitable for addressing this separation challenge, or whether ‘next generation’ separation tools such as multidimensional chromatography may be required. In this example, modifications of results obtained from conventional achiral and chiral chromatography method development screening platforms afford rapid separation of all components for both achiral and chiral analysis, with supercritical fluid chromatography showing the best performance in both cases (1.8 min for separation of six components by achiral SFC and 8.0 min for separation of twelve components by chiral SFC). While other more complex mixtures may require additional tools, these results suggest that new applications of existing separation platforms may be useful for creating the chromatographic methods required to support this new area of synthetic chemistry.
Co-reporter:Xiaodong Bu, Kazunori Koide, Evan J. Carder, and Christopher J. Welch
Organic Process Research & Development 2013 Volume 17(Issue 1) pp:108-113
Publication Date(Web):December 16, 2012
DOI:10.1021/op3003008
Measurement of residual metals in pharmaceutical intermediates is routinely performed using inductively coupled plasma-optical emission spectroscopy (ICP-OES) or inductively coupled plasma-mass spectrometry (ICP-MS). However, these techniques suffer from drawbacks that limit their utility in pharmaceutical process development, including the requirement for expensive instrumentation, complex sample preparation, slow turnaround time, limited sample throughput, and the difficulty of performing the required measurements on the ‘spot’ within pilot plants or manufacturing environments. We investigate the use of a fast and inexpensive high-throughput approach for detection of residual palladium (Pd), based on the Pd-catalyzed Tsuji–Trost deallylation of an allylic ether substrate to produce a highly fluorescent product. We demonstrate the effectiveness of this fluorescence assay for accurate quantitation of Pd levels in a variety of ‘real world’ samples, including mixed oxidation-state samples containing strong Pd ligands.
Co-reporter:Wes Schafer;Simon E. Hamilton;Zainab Pirzada
Chirality 2012 Volume 24( Issue 1) pp:1-4
Publication Date(Web):
DOI:10.1002/chir.21974
Abstract
A simple approach to the automated screening of four different columns on a single gas chromatography (GC) instrument is used for rapid chiral GC method development. Configuration of a conventional GC instrument with a second autosampler and several inexpensive Y-splitters enables simultaneous evaluation of two different columns, allowing a total of four different columns to be evaluated in two automated back to back runs. The resulting system affords a simple and effective approach to chiral GC method development that speeds analysis while eliminating the need for slow and tedious manual interchange of columns. An example of developing a rapid isothermal GC method from the screening results obtained by the instrument is also shown. Chirality, 2011. © 2011 Wiley Periodicals, Inc.
Co-reporter:Zainab Pirzada, Michelle Personick, Mirlinda Biba, Xiaoyi Gong, Lili Zhou, Wes Schafer, Christian Roussel, Christopher J. Welch
Journal of Chromatography A 2010 Volume 1217(Issue 7) pp:1134-1138
Publication Date(Web):12 February 2010
DOI:10.1016/j.chroma.2009.10.004
A systematic approach to the evaluation of new chiral stationary phases (CSPs) for supercritical fluid chromatography (SFC) using a standard library of racemic analytes is described. A standard library of racemic analytes representing a variety of functional group classes was assembled from a mixture of proprietary and commercial compounds. The library is dispensed and stored in a convenient 96-well microplate format to facilitate ease of use, and to minimize the amount of analyte required for analysis. Automated SFC screening was performed on both established CSPs in common use, as well as a group of six recently commercialized CSPs. Screening results were archived in a structure-searchable database that allows convenient comparison of performance data to determine which CSPs shows the best performance.
Co-reporter:Christopher J. Welch, Derek W. Henderson, Brenda Pipik, Mohamed Shaimi, David Schenk and Dave Conlon
Organic Process Research & Development 2010 Volume 14(Issue 4) pp:905-907
Publication Date(Web):May 10, 2010
DOI:10.1021/op100095e
Preparative chromatography was used to overcome the difficult selectivity challenge of accessing a single isomer of a mono tert-butyldimethylsilyl (TBDMS) derivative of an unsymmetrical diol. Chromatographic purification allowed rapid purification of more than 10 kg of the desired intermediate from the statistical mixture of undesired mono-TBDMS, bis-TBDMS, and very strongly retained, unreacted starting material. A noteworthy injection cycle strategy of performing three injections, then desorbing the accumulated strongly bound diol starting material with a strong solvent wash was employed in the separation.
Co-reporter:Christopher J. Welch, Xiaoyi Gong, Wes Schafer, Edwin C. Pratt, Tanja Brkovic, Zainab Pirzada, James F. Cuff, Birgit Kosjek
Tetrahedron: Asymmetry 2010 Volume 21(13–14) pp:1674-1681
Publication Date(Web):14 July 2010
DOI:10.1016/j.tetasy.2010.05.029
An experimental approach for rapid analysis and convenient interpretation of multiparallel experiments is described. Conventional approaches use a series of individual chromatographic runs to produce integrated peak area data, which are stored in individual data files, then transferred to a spreadsheet program and graphed to allow interpretation of experimental results. A simpler and more direct approach utilizes multiple injections within a single chromatographic run to produce a continuous trace of chromatograms, which can often provide a direct visual readout of experimental outcome without the need for peak integration, data transfer, or graphing. In this approach, the chromatogram itself serves as the graph whereby the outcome of the multiparallel experiment can be discerned. The utility of the technique is greatly enhanced by the use of compound-specific detection technologies such as mass spectrometry or chiroptical spectroscopy, and can benefit from experimental designs that facilitate the direct interpretation of results.
Co-reporter:Johnnie L. Leazer Jr., Sean Gant, Anthony Houck, William Leonard and Christopher J. Welch
Environmental Science & Technology 2009 Volume 43(Issue 6) pp:2018-2021
Publication Date(Web):February 6, 2009
DOI:10.1021/es802607a
Supercritical CO2 extraction of aqueous streams is a convenient and effective method to remove commonly used solvents of varying polarities from aqueous waste streams. The resulting aqueous layers can potentially be sewered; whereas the organic layer can be recovered for potential reuse.
Co-reporter:Christopher J. Welch, Derek W. Henderson, David M. Tschaen and Ross A. Miller
Organic Process Research & Development 2009 Volume 13(Issue 3) pp:621-624
Publication Date(Web):March 25, 2009
DOI:10.1021/op900035y
A highly productive method for HPLC preparation of 7.5 kg of an isomerically pure drug intermediate is described. The method employs an IPA/heptane eluent with a Chromegabond Nitro stationary phase, and affords an unusually large productivity of 5.5 kkd (kilograms of desired product per kilogram of stationary phase per day). Details relating to the development and execution of the separation are provided, and possibilities for further improvements are discussed.
Co-reporter:Christopher J. Welch, Xiaoyi Gong, James Cuff, Sarah Dolman, Jason Nyrop, Fiona Lin and Hallena Rogers
Organic Process Research & Development 2009 Volume 13(Issue 5) pp:1022-1025
Publication Date(Web):May 21, 2009
DOI:10.1021/op9001017
The application of a recently developed online HPLC reaction sampling instrument for monitoring flow chemistry reactions is described. The system was found to work well for online analysis of flowing streams at or near atmospheric pressure, allowing for convenient time-based withdrawal, dilution, and HPLC analysis of the output of flow reactors. A general study of the capability of the instrument to sample from flowing streams is presented, along with a detailed study in which the instrument is used to characterize a thermal isomerization reaction carried out using a hot-zone flow reactor.
Co-reporter:Christopher J. Welch
Chirality 2009 Volume 21( Issue 1) pp:114-118
Publication Date(Web):
DOI:10.1002/chir.20625
Abstract
Some recent developments in the use of microscale chiral HPLC for supporting pharmaceutical process research are reviewed, including multiparallel high throughput analysis to support high throughput experimentation studies, rapid multiparallel chromatographic method development, and on-line reaction monitoring. Green chemistry advantages of the approach include greatly reduced solvent consumption, waste generation, and stationary phase requirement relative to conventional chiral HPLC. Chirality, 2009. © 2008 Wiley-Liss, Inc.
Co-reporter:Christopher J. Welch;Xiaoyi Gong;Wes Schafer;Harry Chobanian;Linus Lin;Mirlinda Biba;Ping Liu;Yan Guo ;Adam Beard
Chirality 2009 Volume 21( Issue 1E) pp:E105-E109
Publication Date(Web):
DOI:10.1002/chir.20785
Abstract
A novel family of atropisomers based on a conformationally constrained seven membered ring system is investigated using a combination of preparative chiral chromatography, circular dichroism, and other analytical techniques. The influence of structure on the rate of atropisomer interconversion was explored with a series of analogs showing a range of interconversion rates ranging from very fast (undetectable on the HPLC timescale) to very slow (half life of many days). Chirality 21:E105–E109, 2009. © 2009 Wiley-Liss, Inc.
Co-reporter:Christopher J. Welch, William R. Leonard, Derek W. Henderson, Benjamin Dorner, Karla Glaser Childers, John Y. L. Chung, Frederick W. Hartner, Jennifer Albaneze-Walker and Peter Sajonz
Organic Process Research & Development 2008 Volume 12(Issue 1) pp:81-87
Publication Date(Web):January 1, 2008
DOI:10.1021/op700191z
A screening approach for identifying adsorbents and conditions for selective removal of colored impurities from solutions of pharmaceutical intermediates is described. In this method, a variety of process adsorbents are evaluated using a combination of HPLC or LC−MS and 96-well microplate UV–vis spectroscopy. Several representative examples are shown that illustrate the use of the technique for the selective removal of colored impurities from pharmaceutical development candidates or related intermediates.
Co-reporter:Christopher J. Welch, Peter Sajonz, Glenn Spencer, William Leonard, Derek Henderson, Wes Schafer and Frank Bernardoni
Organic Process Research & Development 2008 Volume 12(Issue 4) pp:674-677
Publication Date(Web):June 11, 2008
DOI:10.1021/op800107u
The use of microscale HPLC for piloting the large-scale preparative chromatographic resolution of the enantiomers of a chiral pharmaceutical intermediate is reported with an example of a millionfold scale-up from a 300 μm i.d. column to a 30 cm i.d column. Performance and productivity at scale are accurately predicted by the microscale approach, which consumes only a small fraction of the material typically used for conventional loading studies. These results suggest a great potential for use of microscale HPLC loading studies during early synthetic route investigations, when only a small amount of sample is typically available.
Co-reporter:Christopher J. Welch;Myung Ho Hyun;Takateru Kubota;Wes Schafer;Frank Bernardoni;Hee Jung Choi;Naijun Wu;Xiaoyi Gong;Bruce Lipshutz
Chirality 2008 Volume 20( Issue 7) pp:815-819
Publication Date(Web):
DOI:10.1002/chir.20548
Abstract
The small column size (0.3 mm i.d. × 15 cm) used in microscale HPLC contains only a small fraction (<1%) of the chromatographic packing material of a typical analytical HPLC column. Consequently, chromatographic stationary phases that are prohibitively expensive in conventional HPLC, owing either to synthetic complexity or costly starting materials, may become commercially viable in the microscale format. To illustrate this point, a previously described, synthetically complex, crown ether chiral stationary phase was prepared and evaluated in the microscale format, showing excellent separation of the enantiomers of underivatized amine analytes. Chirality 2008. © 2008 Wiley-Liss, Inc.
Co-reporter:Wes A. Schafer, Steve Hobbs, Jason Rehm, David A. Rakestraw, Charles Orella, Mark McLaughlin, Zhihong Ge and Christopher J. Welch
Organic Process Research & Development 2007 Volume 11(Issue 5) pp:870-876
Publication Date(Web):August 8, 2007
DOI:10.1021/op7000854
A mobile HPLC reaction monitoring tool consisting of a cart-mounted microfluidic HPLC instrument equipped with a tethered, automated sampling and dilution module is described. Several examples of the use of the instrument for carrying out reaction progress analysis are presented. Reaction aliquot size is typically only a few microliters, allowing extensive sample monitoring from small volume reactions. Reaction quenching is possible, and aliquot dilution is adjustable, with suitable precision and accuracy even at hundredfold dilution. A sampling capillary with a chemically inert stainless steel fritted terminus allows sampling from some heterogeneous reactions. The sampling interval is adjustable, from a minimum of about 4 min, upwards. Visualization of an ongoing or completed study as either stacked “waterfall” chromatograms or as graphs of integrated peak areas (or any derived function, such as percent ee or percent conversion) vs time affords the process chemist valuable information on reaction kinetics and a useful record of reaction progress over time. While online HPLC analysis has been known for some time, the compact and mobile nature of this instrument renders it especially useful for carrying out reaction progress monitoring in the laboratory environment.
Co-reporter:Mirlinda Biba;Peter Sajonz
Chirality 2007 Volume 19(Issue 1) pp:34-43
Publication Date(Web):6 NOV 2006
DOI:10.1002/chir.20336
The Soai reaction system possesses a remarkable combination of characteristics (enantioselective autocatalysis, strong positive nonlinearity leading to asymmetric amplification, ability to be triggered by wide variety of exogenous enantioenriched materials) that make it a potential starting point for a generalized detector for enantioenrichment. In this study we apply standard approaches used in pharmaceutical process research to the problem of developing a rapid method for analysis of the enantiopurity of the Soai reaction product. Several methods for rapid analysis (<1 min per sample) are described, including an approach using chiral supercritical fluid chromatography (SFC) and an approach using achiral chromatography with circular dichroism (CD) detection. Some thoughts on incorporation into a device for generalized enantioenrichment detection are presented. Chirality, 2006. © 2006 Wiley-Liss, Inc.
Co-reporter:Christopher J. Welch;Mirlinda Biba;Paul Hosek;Paul Augustine;Joseph R. Gouker;Gary Kath
Chirality 2007 Volume 19(Issue 3) pp:184-189
Publication Date(Web):27 DEC 2006
DOI:10.1002/chir.20357
A tool for improved tandem column chiral supercritical fluid chromatography (SFC) method development screening was prepared by modification of a commercial analytical SFC instrument with two different software-controllable, six position high-pressure column selection valves, each controlling a bank of five different columns and a pass through line. The resulting instrument, which has the ability to screen 10 different individual columns and 25 different tandem column arrangements, is a useful tool for facilitating the screening of tandem column SFC arrangements for separation of complex mixtures of stereoisomers or other multicomponent mixtures. Strategies for optimal use of the instrument are discussed, and several examples of the use of the instrument in developing tandem SFC methods for resolution of multicomponent mixtures are presented. Chirality, 2007. © 2006 Wiley-Liss, Inc.
Co-reporter:Christopher J. Welch;Peter Sajonz;Jacob Fairchild
Chirality 2007 Volume 19(Issue 8) pp:607-611
Publication Date(Web):9 NOV 2006
DOI:10.1002/chir.20348
The stability of Chiralpak AD chiral stationary phase under various solvent conditions was investigated. An analytical method for the detection of the presence of solubilized Chiralpak AD coating was developed using CD spectroscopy (CD signal at 245 nm). In addition, NMR analysis of the solubilized polymer revealed a characteristic signal for the 3,5-dimethylphenyl carbamate methyl protons at around 2.5 ppm. Both of these methods may be helpful in detecting contamination by the Chiralpak AD polymer or in the study of CSP solvent compatibility. Chirality 19:607–611, 2006 © 2006 Wiley-Liss, Inc.
Co-reporter:Glenn A. Spencer;William R. Leonard Jr.;Osama S. Sudah;Ross A. Miller;Mirlinda Biba;Derek W. Henderson
Chirality 2007 Volume 19(Issue 9) pp:693-700
Publication Date(Web):12 MAR 2007
DOI:10.1002/chir.20378
The modern use of preparative chromatography in pharmaceutical development is illustrated by the case of a recent preclinical candidate from these laboratories. The synthesis of the candidate employed a coupling of two enantiopure intermediates, each of which could be resolved using preparative chiral chromatography. SFC screening was employed to identify the enantioselective stationary phases, and semipreparative SFC methods derived from this screening were used to produce gram amounts of enantiopure intermediate for initial studies. However, initial larger scale resolution required the translation of the SFC methods to HPLC conditions. Preparative chiral HPLC on a 30-cm i.d. column was then used to produce enantiopure intermediates which were coupled to give 170 g of the preclinical candidate. Subsequent preparation of the candidate at larger scale for later-stage clinical evaluation employed an improved synthesis in which one component was constructed by asymmetric synthesis. Resolution of the other component, now a more advanced intermediate, was carried out using newly obtained large-scale SFC equipment. Some discussion is presented on the varying strategies whereby preparative chiral chromatography can be used to support either short-term or long-term synthetic goals in preclinical pharmaceutical development. Chirality, 2007. © 2007 Wiley-Liss, Inc.
Co-reporter:Christopher J. Welch;Qiang Tu;Tiebang Wang;Conrad Raab;Peng Wang;Xiujuan Jia;Xiaodong Bu;Darren Bykowski;Benjamin Hohenstaufen;Michael P. Doyle
Advanced Synthesis & Catalysis 2006 Volume 348(Issue 7-8) pp:
Publication Date(Web):5 MAY 2006
DOI:10.1002/adsc.200505438
HPLC with ICP-MS or ESI-MS detection has been used to investigate metal-containing reaction intermediates in the ligand exchange process leading to formation of the well known Rh2(MEPY)4 catalyst. A variety of intermediates are observed along the pathway to formation of the desired tetrasubstituted product, including isomeric species from di-, tri-, or tetrasubstitution that were previously believed to be absent.
Co-reporter:Mirlinda Biba;Peter Sajonz;William R. Leonard Jr.;Xiaoyi Gong
Chirality 2006 Volume 18(Issue 10) pp:803-813
Publication Date(Web):11 AUG 2006
DOI:10.1002/chir.20325
The Eksigent Express 800 8-channel microfluidic HPLC system was investigated for carrying out multiparallel screening and development of fast normal phase chiral separations. In contrast to the familiar automated sequential chiral method development approaches that often afford a next day result, the multiparallel approach offers the exciting possibility of near “real time” method development, often affording an optimized method in less than 1 h. In this study, four column types (300 μm i.d.) with two different mobile phases are screened using a universal standard gradient approach. Interestingly, parallel method optimization following initial screening was shown to sometimes lead to surprising and unanticipated outcomes, emphasizing the value of the multiparallel screening approach. A variety of standard test racemates were analyzed, with optimized separation methods for most in the 1- to 2-min range. These results compare favorably with results obtained on a single channel conventional HPLC system using 4.6-mm i.d. columns. In addition, isocratic methods developed on the microbore columns are readily translated to the larger column format. Chirality, 2006. © 2006 Wiley-Liss, Inc.
Co-reporter:Audrey Wong, Christopher J. Welch, Jeffrey T. Kuethe, Enrique Vazquez, Mohamed Shaimi, Derek Henderson, Ian W. Davies and David L. Hughes
Organic & Biomolecular Chemistry 2004 vol. 2(Issue 2) pp:168-174
Publication Date(Web):20 Nov 2003
DOI:10.1039/B312180C
A facile preparation of enantiopure ethyl (1S,5S,6S)-6-fluoro-2-oxobicyclo[3.1.0]hexane-6-carboxylate 1 is described. The key feature of the synthesis involves copper-catalyzed enantioselective intramolecular cyclopropanation of a diazoketone to form endo-fluorocyclopropane 1 in a single operation. Removal of a problematic chloroketone impurity using a reactive resin treatment enabled a high throughput enantiopurity upgrade by chiral HPLC. The development of a scalable synthesis of 1 is presented, including details of the selection of catalyst and ligand optimization, incorporation of a reactive resin treatment and selection of chiral HPLC media and conditions.
Co-reporter:Christopher J. Welch;Michael H. Kress;Maria Beconi;David J. Mathre
Chirality 2003 Volume 15(Issue 2) pp:143-147
Publication Date(Web):7 JAN 2003
DOI:10.1002/chir.10180
The enantiomers of the stereolabile peroxisome proliferator-activated receptor (PPAR) agonist, 1, were isolated by preparative chiral chromatography and their absolute configuration established using a combination of chromatographic and NMR methods. Enantiomer interconversion was investigated under a variety of conditions, with rapid racemization being observed in most solvents, including all aqueous systems studied, irrespective of pH. Rapid racemization in both dog and human plasma was confirmed by chiral HPLC with MS detection. Chirality 15:143–147, 2003. © 2003 Wiley-Liss, Inc.
Co-reporter:Christopher J. Welch;Mohamed Shaimi;Ronald H. Szumigala Jr.;Mirlinda Biba;Jennifer R. Chilenski;Ulf Dolling;Paul J. Reider;David J. Mathre
Journal of Separation Science 2002 Volume 25(Issue 13) pp:847-850
Publication Date(Web):19 SEP 2002
DOI:10.1002/1615-9314(20020901)25:13<847::AID-JSSC847>3.0.CO;2-2
A microplate-based assay to rapidly identify adsorbents suitable for removing process impurities is described. A solution containing both product and impurity is added to a number of wells, each containing a small amount of a candidate adsorbent. After equilibration, analysis of the supernatant solution allows one to determine the extent of adsorption of both product and impurity. Fast analysis techniques such as flow injection analysis LC-MS or the use of colorimetric indicators allows rapid identification of the most selective adsorbents for a given separation problem.
Co-reporter:Xiaodong Bu, Michael Williams, Junyong Jo, Kazunori Koide and Christopher J. Welch
Chemical Communications 2017 - vol. 53(Issue 4) pp:NaN723-723
Publication Date(Web):2016/12/12
DOI:10.1039/C6CC08562H
Rapid palladium (Pd) catalyzed deallylation of an uncoloured reagent within a flowing stream affords a dose dependent colour formation that can be used for convenient online analysis of trace levels of Pd contamination using a modified HPLC instrument. An application to the online sensing of Pd breakthrough from a flow through Pd adsorption cartridge is described. An alternative configuration of the instrumentation allows the rapid (<1 min) and accurate measurement of Pd levels within samples injected via a conventional HPLC autosampler.
Co-reporter:Christopher J. Welch, Kerstin Zawatzky, Alexey A. Makarov, Satoshi Fujiwara, Arimasa Matsumoto and Kenso Soai
Organic & Biomolecular Chemistry 2017 - vol. 15(Issue 1) pp:NaN101-101
Publication Date(Web):2016/09/28
DOI:10.1039/C6OB01939K
An investigation is reported on the use of the autocatalytic enantioselective Soai reaction, known to be influenced by the presence of a wide variety of chiral materials, as a generic tool for measuring the enantiopurity and absolute configuration of any substance. Good generality for the reaction across a small group of test analytes was observed, consistent with literature reports suggesting a diversity of compound types that can influence the stereochemical outcome of this reaction. Some trends in the absolute sense of stereochemical enrichment were noted, suggesting the possible utility of the approach for assigning absolute configuration to unknown compounds, by analogy to closely related species with known outcomes. Considerable variation was observed in the triggering strength of different enantiopure materials, an undesirable characteristic when dealing with mixtures containing minor impurities with strong triggering strength in the presence of major components with weak triggering strength. A strong tendency of the reaction toward an ‘all or none’ type of behavior makes the reaction most sensitive for detecting enantioenrichment close to zero. Consequently, the ability to discern modest from excellent enantioselectivity was relatively poor. While these properties limit the ability to obtain precise enantiopurity measurements in a simple single addition experiment, prospects may exist for more complex experimental setups that may potentially offer improved performance.
Co-reporter:Chandan L. Barhate, Leo A. Joyce, Alexey A. Makarov, Kerstin Zawatzky, Frank Bernardoni, Wes A. Schafer, Daniel W. Armstrong, Christopher J. Welch and Erik L. Regalado
Chemical Communications 2017 - vol. 53(Issue 3) pp:NaN512-512
Publication Date(Web):2016/11/18
DOI:10.1039/C6CC08512A
Recent developments in fast chromatographic enantioseparations now make high throughput analysis of enantiopurity on the order of a few seconds achievable. Nevertheless, routine chromatographic determinations of enantiopurity to support stereochemical investigations in pharmaceutical research and development, synthetic chemistry and bioanalysis are still typically performed on the 5–20 min timescale, with many practitioners believing that sub-minute enantioseparations are not representative of the molecules encountered in day to day research. In this study we develop ultrafast chromatographic enantioseparations for a variety of pharmaceutically-related drugs and intermediates, showing that sub-minute resolutions are now possible in the vast majority of cases by both supercritical fluid chromatography (SFC) and reversed phase liquid chromatography (RP-LC). Examples are provided illustrating how such methods can be routinely developed and used for ultrafast high throughput analysis to support enantioselective synthesis investigations.
Co-reporter:
Analytical Methods (2009-Present) 2014 - vol. 6(Issue 3) pp:NaN862-862
Publication Date(Web):2013/12/10
DOI:10.1039/C3AY41953C
The advantages of MISER LC-MS (high throughput, simple readout of results) are demonstrated in the analysis of E-capsaicin in chili peppers and hot sauces. The ready availability of samples with a wide range of capsaicin content and the fast and easy detection using the MISER (Multiple Injections in a Single Experimental Run) technique makes this a potentially useful experiment to introduce novices to the important analytical technique of LC-MS. In this study we describe a simple and rapid chromatographic method for evaluation of E-capsaicin in chili peppers using HPLC with 80% organic eluent in a Poroshell SB-C18 column coupled with electrospray ionization mass spectrometry detection and MISER analysis. The misergrams obtained from continuous sample injections every 0.73 min allow the convenient simultaneous visualization of the outcomes of multiple experiments represented as single chromatograms. A considerable variation in E-capsaicin levels is clearly visualized among different types of peppers and sauces, with the ghost pepper (Bhut Jolokia) showing the highest E-capsaicin concentration of the peppers sampled.
Co-reporter:Erik L. Regalado, Marisa C. Kozlowski, John M. Curto, Tobias Ritter, Michael G. Campbell, Anthony R. Mazzotti, Bruce C. Hamper, Christopher D. Spilling, Michael P. Mannino, Li Wan, Jin-Quan Yu, Jinchu Liu and Christopher J. Welch
Organic & Biomolecular Chemistry 2014 - vol. 12(Issue 14) pp:NaN2166-2166
Publication Date(Web):2014/02/20
DOI:10.1039/C3OB42195C
The use of state-of-the-art separation tools from the pharmaceutical industry for addressing intractable separation problems from academic synthetic chemistry is evaluated, showing fast and useful results for the resolution of complex mixtures, separation of closely related components, visualization of difficult to detect compounds and purification of synthetic intermediates. Some recommendations for potential near term deployment of separation tools within academia and the evolution of next generation separation technologies are discussed.
![6H,12H-5,11-Methanodibenzo[b,f][1,5]diazocine,2,8-dimethyl-, (5S,11S)-](/data/chemimg/20600/21451-74-1.png)
![6H,12H-5,11-Methanodibenzo[b,f][1,5]diazocine,2,8-dimethyl-, (5S,11S)-](/data/chemimg/20600/21451-74-1_b.png)