Don M. Coltart

Find an error

Name: Coltart, Don

Organization: University of Houston , USA

Department: Department of Chemistry

Title: Assistant(PhD)

TOPICS

Organic Chemistry

Amination

Chemicals
References

On the regioselectivity and diastereoselectivity of ACC hydrazone alkylation

Co-reporter:Uyen Huynh, Md. Nasir Uddin, Sarah E. Wengryniuk, Stacey L. McDonald, Don M. Coltart

Tetrahedron 2017 Volume 73(Issue 5) pp:432-436

Publication Date(Web):2 February 2017

DOI:10.1016/j.tet.2016.11.064

The asymmetric α-allylation of 3-pentanone using several different N-amino cyclic carbamate (ACC) auxiliaries is described. The level of asymmetric induction was found to range from er = 93:7 to er = 99:1. The factors that lead to compromised selectivity for the various auxiliaries have been determined. Significantly, we have established that using the easily accessible and inexpensive valine-derived ACC auxiliary, it is possible to obtain synthetically useful levels of asymmetric induction (er = 96:4).

Asymmetric Induction in Hydroacylation by Cooperative Iminium Ion–Transition-Metal Catalysis

Co-reporter:Ettore J. Rastelli, Ngoc T. Truong, and Don M. Coltart

Organic Letters 2016 Volume 18(Issue 21) pp:5588-5591

Publication Date(Web):October 21, 2016

DOI:10.1021/acs.orglett.6b02825

A new strategy for the rhodium-catalyzed enantioselective hydroacylation is described. This has been achieved through the merger of iminium ion catalysis and transition-metal catalysis such that asymmetric induction derives from a readily accessible, inexpensive chiral nonracemic secondary amine catalyst rather than a chiral nonracemic phosphine as is typical of conventional asymmetric hydroacylation methods.

Direct carbon–carbon bond formation via reductive soft enolization: a syn-selective Mannich addition of α-iodo thioesters

Co-reporter:Ngoc Truong, Scott J. Sauer, Cyndie Seraphin-Hatcher and Don M. Coltart

Organic & Biomolecular Chemistry 2016 vol. 14(Issue 33) pp:7864-7868

Publication Date(Web):28 Jul 2016

DOI:10.1039/C6OB01244B

The β-amino carboxylic acid moiety is a key feature of numerous important biologically active compounds. We describe a syn-selective direct Mannich addition reaction that uses α-iodo thioesters and sulfonyl imines and produces β-amino thioesters. Enolate formation is achieved by reductive soft enolization. The products of the reaction provide straightforward access to biologically important β-lactams through a variety of known reactions.

A simple and efficient approach to the N-amination of oxazolidinones using monochloroamine

Co-reporter:Uyen Huynh, Md. Nasir Uddin, Sarah E. Wengryniuk, Stacey L. McDonald, Don M. Coltart

Tetrahedron Letters 2016 Volume 57(Issue 43) pp:4799-4802

Publication Date(Web):26 October 2016

DOI:10.1016/j.tetlet.2016.09.034

•Mild and atom economical amination.•Generation of ACC auxiliaries.•Acylhydrazide synthesis.Chiral nonracemic N-amino cyclic carbamates (ACCs) are important auxiliaries for certain asymmetric transformations. In the past they have been synthesized from oxazolidinones using methods that require the preparation and use of non-atom economical aminating agents that can be difficult to prepare, and often strong bases. In what follows we describe a mild and operationally simple method for the direct N-amination of oxazolidinones that use NH2Cl derived from commercial bleach.

Asymmetric Synthesis of (+)-anti- and (−)-syn-Mefloquine Hydrochloride

Co-reporter:Ettore J. Rastelli and Don M. Coltart

The Journal of Organic Chemistry 2016 Volume 81(Issue 20) pp:9567-9575

Publication Date(Web):September 22, 2016

DOI:10.1021/acs.joc.6b01476

The asymmetric (er > 99:1) total synthesis of (+)-anti- and (−)-syn-mefloquine hydrochloride from a common intermediate is described. The Sharpless asymmetric dihydroxylation is the key asymmetric transformation used in the synthesis of this intermediate. It is carried out on an olefin that is accessed in three steps from commercially available materials, making the overall synthetic sequence very concise. The common diol intermediate derived from the Sharpless asymmetric dihydroxylation is converted into either a trans- or cis-epoxide, and these are subsequently converted to (+)-anti- and (−)-syn-mefloquine, respectively. X-ray crystallographic analysis of derivatives of (+)-anti- and (−)-syn-mefloquine is used to lay to rest a 40 year argument regarding the absolute stereochemistry of the mefloquines. A formal asymmetric (er > 99:1) synthesis of (+)-anti-mefloquine hydrochloride is also presented that uses a Sharpless asymmetric epoxidation as a key step.

Asymmetric synthesis of structural analogues of (+)-clusianone via enantioselective ACC alkylation

Co-reporter:Michelle R. Garnsey, Maulen M. Uteuliyev, Don M. Coltart

Tetrahedron Letters 2015 Volume 56(Issue 23) pp:3183-3185

Publication Date(Web):3 June 2015

DOI:10.1016/j.tetlet.2015.01.012

The asymmetric total synthesis of four structural analogues of (+)-clusianone from a common advanced intermediate is described. Asymmetric induction is achieved through the use of enantioselective ACC alkylation, providing the common advanced intermediate with an er of 99:1.

The apratoxin marine natural products: isolation, structure determination, and asymmetric total synthesis

Co-reporter:Emily M. Tarsis, Ettore J. Rastelli, Sarah E. Wengryniuk, Don M. Coltart

Tetrahedron 2015 Volume 71(Issue 31) pp:5029-5044

Publication Date(Web):5 August 2015

DOI:10.1016/j.tet.2015.05.047

A Concise and Highly Enantioselective Total Synthesis of (+)-anti- and ()-syn-Mefloquine Hydrochloride: Definitive Absolute Stereochemical Assignment of the Mefloquines

Co-reporter:Ettore J. Rastelli ; Don M. Coltart

Angewandte Chemie 2015 Volume 127( Issue 47) pp:14276-14280

Publication Date(Web):

DOI:10.1002/ange.201507304

Abstract

A concise asymmetric (>99:1 e.r.) total synthesis of (+)-anti- and (−)-syn-mefloquine hydrochloride from a common intermediate is described. The key asymmetric transformation is a Sharpless dihydroxylation of an olefin that is accessed in three steps from commercially available materials. The Sharpless-derived diol is converted into either a trans or cis epoxide, and these are subsequently converted into (+)-anti- and (−)-syn-mefloquine, respectively. The synthetic (+)-anti- and (−)-syn-mefloquine samples were derivatized with (S)-(+)-mandelic acid tert-butyldimethylsilyl ether, and a crystal structure of each derivative was obtained. These are the first X-ray structures for mefloquine derivatives that were obtained by coupling to a known chiral, nonracemic compound, and provide definitive confirmation of the absolute stereochemistry of (+)-anti- as well as (−)-syn-mefloquine.

A Concise and Highly Enantioselective Total Synthesis of (+)-anti- and ()-syn-Mefloquine Hydrochloride: Definitive Absolute Stereochemical Assignment of the Mefloquines

Co-reporter:Ettore J. Rastelli ; Don M. Coltart

Angewandte Chemie International Edition 2015 Volume 54( Issue 47) pp:14070-14074

Publication Date(Web):

DOI:10.1002/anie.201507304

Abstract

Asymmetric anti-aldol addition of achiral ketones via chiral N-amino cyclic carbamate hydrazones

Co-reporter:John D. Knight and Don M. Coltart

Chemical Communications 2013 vol. 49(Issue 68) pp:7495-7497

Publication Date(Web):04 Jul 2013

DOI:10.1039/C3CC44716B

The asymmetric anti-aldol addition of ketone-derived donors and aldehyde acceptors is described. Asymmetric induction is achieved through the use of chiral N-amino cyclic carbamate (ACC) auxiliaries. The transformation exhibits essentially perfect anti-diastereoselectivity and enantioselectivity, and has the unusual feature of proceeding via thermodynamic, rather than kinetic control.

Expanding the scope of the asymmetric anti-aldol addition of chiral N-amino cyclic carbamate hydrazones

Co-reporter:John D. Knight, Don M. Coltart

Tetrahedron Letters 2013 Volume 54(Issue 40) pp:5470-5472

Publication Date(Web):2 October 2013

DOI:10.1016/j.tetlet.2013.07.140

An asymmetric anti-aldol addition process of ketone-derived donors that is not limited by the structure of the ketone is described. This is achieved by merging the enantioselective α,α-bisalkylation of N-amino cyclic carbamate (ACC) hydrazones with the asymmetric anti-aldol addition of ACC hydrazones. The products of this process are obtained with essentially perfect stereoselectivity. Using this procedure it is possible to gain access to ketone-based anti-aldol addition products that are inaccessible in a controlled sense via direct aldol methods.

Asymmetric Total Synthesis of Apratoxin D

Co-reporter:Bradley D. Robertson, Sarah E. Wengryniuk, and Don M. Coltart

Organic Letters 2012 Volume 14(Issue 20) pp:5192-5195

Publication Date(Web):October 11, 2012

DOI:10.1021/ol302309c

The first asymmetric total synthesis of the marine natural product apratoxin D, a highly potent inhibitor of H-460 human lung cancer cell growth (IC50 value of 2.6 nM), is described. Asymmetric N-amino cyclic carbamate (ACC) α,α-bisalkylation was utilized to establish the isolated C-37 methyl group with excellent selectivity. Other key asymmetric transformations employed were an Evans syn-aldol and a Paterson anti-aldol, both of which also proceeded with excellent stereoselectivity.

Direct carbon–carbon bond formation via reductive soft enolization: a syn-selective Mannich addition of α-iodo thioesters

Co-reporter:Ngoc Truong, Scott J. Sauer, Cyndie Seraphin-Hatcher and Don M. Coltart

Organic & Biomolecular Chemistry 2016 - vol. 14(Issue 33) pp:NaN7868-7868

Publication Date(Web):2016/07/28

DOI:10.1039/C6OB01244B

Asymmetric anti-aldol addition of achiral ketones via chiral N-amino cyclic carbamate hydrazones

Co-reporter:John D. Knight and Don M. Coltart

Chemical Communications 2013 - vol. 49(Issue 68) pp:NaN7497-7497

Publication Date(Web):2013/07/04

DOI:10.1039/C3CC44716B