The synthesis of neopeltolide analogues that contain variations in the oxazole-containing side chain and in the macrolide core are reported along with the GI50 values for these compounds against MCF-7, HCT-116, and p53 knockout HCT-116 cell lines. Although biological activity is sensitive to changes in the macrocycle and the side chain, several analogues displayed GI50 values of <25 nM. Neopeltolide and several of the more potent analogues were significantly less potent against p53 knockout cells, suggesting that p53 plays an auxiliary role in the activity of these compounds.

The potent cytotoxins pederin and psymberin have been prepared through concise synthetic routes (10 and 14 steps in the longest linear sequences, respectively) that proceed via a late-stage multicomponent approach to construct the N-acyl aminal linkages. This route allowed for the facile preparation of a number of analogs that were designed to explore the importance of the alkoxy group in the N-acyl aminal and functional groups in the two major subunits on biological activity. These analogs, including a pederin/psymberin chimera, were analyzed for their growth inhibitory effects, revealing several new potent cytotoxins and leading to postulates regarding the molecular conformational and hydrogen bonding patterns that are required for biological activity. Second generation analogs have been prepared based on the results of the initial assays and a structure-based model for the binding of these compounds to the ribosome. The growth inhibitory properties of these compounds are reported. These studies show the profound role that organic chemistry in general and specifically late-stage multicomponent reactions can play in the development of unique and potent effectors for biological responses.

The dictyostatins are a promising class of potential anti-cancer drugs because they are powerful microtubule-stabilizing agents, but the complexity of their chemical structures is a severe impediment to their further development. On the basis of both synthetic and medicinal chemistry analyses, 16-desmethyl-25,26-dihydrodictyostatin and its C6 epimer were chosen as potentially potent yet accessible dictyostatin analogues, and three new syntheses were developed. A relatively classical synthesis involving vinyllithium addition and macrocyclization gave way to a newer and more practical approach based on esterification and ring-closing metathesis reaction. Finally, aspects of these two approaches were combined to provide a third new synthesis based on esterification and Nozaki−Hiyama−Kishi reaction. This was used to prepare the target dihydro analogues and the natural product. All of the syntheses are streamlined because of their high convergency. The work provided several new analogues of dictyostatin, including a truncated macrolactone and a C10 E-alkene, which were 400- and 50-fold less active than (−)-dictyostatin, respectively. In contrast, the targeted 16-desmethyl-25,26-dihydrodictyostatin analogues retained almost complete activity in preliminary biological assays.

The polyketide natural product (+)-discodermolide is a potent microtubule stabilizer that has generated considerable interest in its synthetic, medicinal, and biological chemistry. It progressed to early clinical oncology trials, where it showed some efficacy in terms of disease stabilization but also some indications of causing pneumotoxicity. Remarkably, there are no reports of its metabolism. Here, we examined its fate in mixed human liver microsomes. Due to limited availability of the agent, we chose a nanoflow liquid chromatography-electrospray ionization-mass spectrometry analytical approach employing quadrupolar ion trap and quadrupole−quadrupole-time-of-flight instruments for these studies. (+)-Discodermolide was rapidly converted to eight metabolites, with the left-side lactone (net oxidation) and the right-side diene (epoxidation followed by hydrolysis, along with an oxygen insertion product) being the most metabolically labile sites. Other sites of metabolism were the allylic and pendant methyl moieties in the C12−C14 region of the molecule. The results provide information on the metabolic soft spots of the molecule and can be used in further medicinal chemistry efforts to optimize discodermolide analogues.

The C-cyclopropylalkylamide scaffold was previously identified as a new structural framework for antiestrogens. A second generation library provided three compounds that bind estrogen receptor (ER)α. Further screening of this library identified an ERβ hit and inspired another round of SAR. A new focused library was tested for binding to the ERs, and for effects on the growth of breast cancer cell lines and protein levels of common cell cycle regulators.

Dual polarization interferometry (DPI) and resonant mirror (RM) methods were used to characterize the growth of microtubules (MTs) on biosensor surfaces. The structure and dynamics of MTs play an important role in cell division and are a target for many anti-cancer drugs. Evidence from DPI demonstrated the growth of MTs on streptavidin–biotinylated-tubulin surfaces from the increase in mass and thickness, with a simultaneous decrease in density. The initial increase in thickness of 0.236 nm/min suggested the elongation of protofilaments before they join laterally to form the MT, where the rate of growth increased to 0.436 nm/min. Continuous mass increases were also observed when tubulin was added to a similar underlying RM surface. Tubulin binding to these surfaces was also temperature dependent, increasing the absolute response with MT stabilizers, while inhibiting binding with destabilizers when temperature was changed from 15 to 37 °C. Finally, the initial rates of tubulin assembly (mean ± SD, n = 3) with MT-stabilizer agents were significantly higher at 1.50 ± 0.27 and 1.04 ± 0.13 arcseconds/s, respectively, compared to 0.37 ± 0.11 arcseconds/s for tubulin containing GTP only. In the presence of the MT destabilizers, colchicine and dolastatin 10, the slopes of initial rates were lower than in their absence at 0.05 ± 0.01 and 0.27 ± 0.08 arcseconds/s, respectively. This provides evidence for the ability of surface-based optical sensors to distinguish between MT stabilizers and destabilizers, while also paving the path to develop other methods to screen for MT-perturbing agents using the same underlying surface engineering.

A new structural scaffold for antiestrogens was identified from the cell-based screening of transcriptional regulation properties of a 67-member library of homoallylic amides, allylic amides, and C-cyclopropylalkylamides. C-Cyclopropylalkylamide 3a (O-ethyl-N-{2-[(1S*,2R*)-2-{(R*)-[(diphenylphosphinoyl)amino](phenyl)methyl}cyclopropyl]ethyl}-N-[(4-methylphenyl)sulfonyl]carbamate) had antagonistic activity similar to that of tamoxifen and was further evaluated. Compound 3a inhibited estradiol-induced proliferation of the ER-positive MCF-7 cells but had no effect on ER-negative MDA-MB231 human breast cancer cells. Furthermore, high micromolar concentrations of 3a exhibited minimal cytotoxicity to the ER-negative line. The biological activities of the enantiomers of 3a did not differ from one another nor from that of racemic 3a.A new structural scaffold for antiestrogens was identified from the cell-based screening of a 67-member library of homoallylic amides, allylic amides, and C-cyclopropylalkylamides. Several derivatives had activity comparable to that of tamoxifen.

Two paclitaxel(Ptx)-resistant ovarian cancer cell lines, 1A9/Ptx-10 and 1A9/Ptx-22, isolated from the 1A9 cell line (a clone of the A2780 line) by continuous exposure to Ptx and verapamil, have point mutations in their major -tubulin gene and in one or both alleles of their TP53 gene. These cells were examined for alterations in cell cycle regulators and the tubulin-binding protein stathmin. Unlike parental cells, neither 1A9/Ptx-10 nor 1A9/Ptx-22 expressed detectable levels of p21WAF1/Cip1, a putative transcriptional regulator of stathmin, but did overexpress stathmin and Bcl2. No differences were noted in the expression levels of proliferative cell nuclear antigen or tyrosine-phosphorylated p34Cdc2. Ptx treatment altered little the expression of stathmin in the parental cell line, although it increased p21WAF1/Cip1 levels several-fold. Infection of Ptx-resistant lines with a wild-type TP53-bearing adenovirus (AdWTp53) changed cell cycle distribution and increased the levels of p21WAF1/Cip1, but caused no changes in stathmin levels. Microtubule drug resistance in ovarian carcinoma may be associated with altered p53/21WAF1/Cip1 regulatory pathways for stathmin expression and function.

Two new highly stereoselective routes to (2R,3S,4R)-3-(tert-butyldimethylsilanyloxy)-2,4-dimethyl-5-oxopentanoic acid methoxymethylamide, an important intermediate in natural product synthesis, are described. Both schemes are considerably shorter and less expensive than methods previously reported. The title compound was then converted to direct precursors of C1–C7 and C17–24 fragments of the potent microtubule stabilizer (+)-discodermolide.Graphic(3R,4S,5S)-4-(tert-Butyldimethylsilanyloxy)-3,5-dimethyltetrahydropyran-2-oneC13H26O3SiMp=55–55.5°C (pentane)[α]D18=+20.4 (c 0.22, CHCl3)Source of chirality: Evans’ auxiliaryAbsolute configuration: 3R,4S,5S(2R,3S,4S,5Z)-3-(tert-Butyldimethylsilanyloxy)-6-iodo-2,4-dimethylhex-5-enoic acid methoxymethylamideC16H32NO3SiI[α]D18=+65.9 (c 1.0, CHCl3)Source of chirality: Evans’ auxiliaryAbsolute configuration: 2R,3S,4S,5Z(2R,3S,4S,5Z)-3-(tert-Butyldimethylsilanyloxy)-2,4-dimethylocta-5,7-dienoic acid methoxymethylamideC18H35NO3Si[α]D18=+53.2 (c 0.01, CHCl3)Source of chirality: Evans’ auxiliaryAbsolute configuration: 2R,3S,4S,5Z(2R,3S,4S,5Z)-3-(tert-Butyldimethylsilanyloxy)-2,4-dimethylocta-5,7-dienalC16H30O2Si[α]D18=−16.7 (c 1.30, CHCl3)Source of chirality: Evans’ auxiliaryAbsolute configuration: 2R,3S,4S,5Z