Facile inversion of configuration of N-Boc-β-aminoalcohols via SN2 cyclization to oxazolidinones

Discovery of 3,5-Diphenyl-4-methyl-1,3-oxazolidin-2-ones as Novel, Potent, and Orally Available Δ-5 Desaturase (D5D) Inhibitors

The discovery and optimization of Δ-5 desaturase (D5D) inhibitors are described. Investigation of the 1,3-oxazolidin-2-one scaffold was inspired by a pharmacophore model constructed from the common features of several hit compounds, resulting in the identification of 3,5-diphenyl-1,3-oxazolidin-2-one 5h as a novel lead showing potent in vitro activity. Subsequent optimization focused on the modification of two metabolic sites, which provided (4S,5S)-5i, a derivative with improved metabolic stability. Moreover, adding a substituent into the upper phenyl moiety further enhanced the intrinsic activity, which led to the discovery of 5-[(4S,5S)-5-(4fluorophenyl)-4-methyl-2-oxo-1,3-oxazolidin-3-yl]benzene-1,3-dicarbonitrile (4S,5S)-5n, endowed with excellent D5D binding affinity, cellular activity, and high oral bioavailability in a mouse. It exhibited robust in vivo hepatic arachidonic acid/dihomo-γ-linolenic acid ratio reduction (a target engagement marker) in an atherosclerosis mouse model. Finally, an asymmetric synthetic procedure for this compound was established.

Straightforward access to spisulosine and 4,5-dehydrospisulosine stereoisomers: probes for profiling ceramide synthase activities in intact cells

A stereoselective synthesis of spisulosine (ES285) and 4,5-dehydrospisulosine stereoisomers is described. Hydrozirconation of 1-pentadecyne with Schwartz reagent, followed by diastereocontrolled addition to L- or D-alaninal afforded the required 2-amino-1,3-diol framework. The resulting sphingoid bases revealed as excellent probes for the profiling of ceramide synthase activity in intact cells. Among the sphingoid bases described in this work, spisulosine (ES285), RBM1-77, and RBM1-73 were the most suitable ones because of their highest acylation rates. These molecules should prove useful to study the role of the different ceramide synthases and the resulting N-acyl (dihydro)ceramides in cell fate.

A survey of the syntheses of active pharmaceutical ingredients for antiretroviral drug combinations critical to access in emerging nations

It has been roughly 25 years since the threat posed by human immunodeficiency virus type 1 (HIV-1) became widely known. The cumulative death toll from HIV/AIDS is now greater than 25 million. There are approximately 33 million people living worldwide with this disease, of whom about 68% (22.5 million) live in sub-Saharan Africa (http://www.avert.org/worldstats.htm). A number of antiretroviral (ARV) drugs have been approved for treatment of HIV/AIDS. Inhibitors of HIV reverse transcriptase (RTIs) include the nucleoside/nucleotide drugs zidovudine, lamivudine, abacavir, didanosine, stavudine, emtricitabine and tenofovir disoproxil fumarate. Non-nucleoside RTIs include nevirapine, efavirenz and etravirine. Inhibitors of HIV protease (PIs) include saquinavir, ritonavir, lopinavir, nelfinavir, indinavir, fosamprenavir and atazanavir. Enfuvirtide inhibits the HIV fusion protein. The CCR5 chemokine antagonist maraviroc and the integrase inhibitor raltegravir were very recently approved by the US FDA. Fixed-dose combinations (FDCs) have been formulated to increase tolerability, convenience and compliance. First-line drug combinations are offered to treatment-naive patients, while second-line drugs are reserved for those who no longer respond adequately to first-line therapy. In developing countries a modest but increasing fraction of those infected have access to ARVs. The Clinton HIV/AIDS Initiative estimates that 2.4 million of the nearly 8 million individuals needing treatment in developing nations have access to some drugs. First-line FDCs used in resource-poor settings are largely combinations of two nucleoside RTIs and a non-nucleoside RTI or PI. The effectiveness of these combinations decreases over time, requiring a switch to combinations that retain potency in the presence of viral resistance. Increasing access to second-line FDCs and new developments in first-line ARV therapy are cost challenges. In high-income countries the cost of ARV therapy is largely irrelevant, except for "advanced salvage" drugs such as enfuvirtide. In resource-poor settings cost is a huge factor that limits drug access, resulting in high rates of new infection and subsequent mortality. IP coverage, where granted, can keep access prices for essential ARVs higher than would otherwise be the case. Large, innovator companies have made drugs available at prices very close to the cost of manufacturing for "lowest income" countries. Generic providers in India and elsewhere provide the largest supply of drugs for the developing world. The recent issuance of Voluntary and Compulsory Licenses (VLs, CLs) through the World Trade Organization's TRIP (Treaty Respecting Intellectual Property) provisions arguably contribute to bringing down access prices. The utilization of improved science, pooled purchasing and intelligent procurement practices all definitely contribute to access. This work surveys the production processes for several critical ARVs. These are discussed in terms of scale up, raw material/intermediates and active pharmaceutical ingredient (API) costs. In some cases new routes to APIs or critical intermediates are needed. Based on potential new chemistries, there are significant opportunities to reduce cost for a number of critical ARVs.

Catalyst-Free Chemoselective N-tert-Butyloxycarbonylation of Amines in Water

[Structure: see text] Catalyst-free N-tert-butyloxycarbonylation of amines in water is reported. The N-t-Boc derivatives were formed chemoselectively without any isocyanate, urea, N,N-di-t-Boc, and O/S-t-Boc as side products. Chiral amines, esters of alpha-amino acids, and beta-amino alcohol afforded optically pure N-t-Boc derivatives. Amino alcohol and 2-aminophenol afforded the N-t-Boc derivative without oxazolidinone formation. Selectivity was observed during competition of aromatic amine vs aliphatic amine, amine vs amino acid ester, amine vs amino alcohol, and primary amine vs secondary amine.

Fungal Aerobic Reductive Dechlorination of Ethyl 2-Chloroacetoacetate by Saccharomyces cerevisiae: Mechanism of a Novel Type of Microbial Dehalogenation

Saccharomyces cerevisiae reduces the beta-keto ester ethyl 2-chloroacetoacetate to the respective chiral cis- and trans-beta-hydroxy esters. In the course of chiral reduction, competing dehalogenation of the xenobiotic substrate to ethyl acetoacetate occurs, in a reaction mediated by cytosolic glutathione (GSH). Mechanistically, the dechlorination is a novel type of glutathione-dependent dehalogenation catalysed by an as yet unidentified glutathione-dependent dehalogenase. The first step consists of a nucleophilic replacement of the chloride substituent by glutathione. In the subsequent enzyme-catalysed step, a second glutathione molecule liberates the dehalogenation product by thiolytic attack at the thioether bridge, resulting in a net transfer of two electrons to the substrate and in the formation of glutathione disulfide (GSSG). Being effective under aerobic conditions and catalysed by a fungus, this reductive dechlorination of an aliphatic substrate is an outstanding example of a novel, glutathione-mediated microbial dehalogenation.

Highly diastereoselective anti-aldol reactions utilizing the titanium enolate of cis-2-arylsulfonamido-1- acenaphthenyl propionate

[reaction: see text] anti-Aldol reaction of Ti-enolate derived from cis-2-arylsulfonamido-1-acenaphthenyl propionate with representative aldehydes proceeded in excellent yield with high diastereoselectivity. Both enantiomers of cis-2-amino-1-acenaphthenol were synthesized employing lipase-catalyzed kinetic resolution as the key step.

A novel synthesis of 5-functionalized oxazolidin-2-ones from enantiomerically pure 2-substituted N-[(R)-(+)-alpha-methylbenzyl]aziridines

5-Funtionalized enantiomerically pure oxazolidin-2-ones were prepared in one pot from commercially available chiral aziridines bearing an electron-withdrawing group at C-2 with retention of the configuration in high yields by regioselective aziridine ring-opening followed by intramolecular cyclization.