Efficient access to enantiomerically pure cyclic alpha-amino esters through a lipase-catalyzed kinetic resolution

Current applications of kinetic resolution in the asymmetric synthesis of substituted pyrrolidines

Chiral substituted pyrrolidines are key elements in various biologically active molecules and are therefore valuable synthetic targets. One traditional method towards enantiomerically pure compounds is the application of kinetic resolution. In this review, current KR methodology used in the synthesis of substituted pyrrolidines is surveyed, including enzymatic methods, cycloadditions and reduction of ketones.

Discovery of Indoline-2-carboxamide Derivatives as a New Class of Brain-Penetrant Inhibitors of Trypanosoma brucei

There is an urgent need for new, brain penetrant small molecules that target the central nervous system second stage of human African trypanosomiasis (HAT). We report that a series of novel indoline-2-carboxamides have been identified as inhibitors of Trypanosoma brucei from screening of a focused protease library against Trypanosoma brucei brucei in culture. We describe the optimization and characterization of this series. Potent antiproliferative activity was observed. The series demonstrated excellent pharmacokinetic properties, full cures in a stage 1 mouse model of HAT, and a partial cure in a stage 2 mouse model of HAT. Lack of tolerability prevented delivery of a fully curative regimen in the stage 2 mouse model and thus further progress of this series.

lip2, a novel lipase gene cloned from Aspergillus niger exhibits enzymatic characteristics distinct from its previously identified family member

We have cloned a novel lipase gene, lip2, from Aspergillus niger and expressed it in Escherichia coli. Upon purification of the recombinant Lip2 protein, its properties were characterized. In comparison with a previously identified lipase Lip1, both enzymes are acid lipases (optimal pH <6.5), Ca(2+)-dependent and PMSF-sensitive, but have different molecular weights (35 and 43 kDa), optimal substrate spectra (C10 and C8), optimal reaction temperatures (45 and 50 degrees C) and thermal stability. Circular dichroism spectroscopy revealed that Lip2 contains a typical Ca(2+)-active site. This first report on the cloning of the Lip2 gene and its enzymatic characteristics may greatly facilitate its potential industrial application.

A straightforward route to enantiopure alpha-substituted derivatives of (2S,3aS,7aS)-octahydroindole-2-carboxylic acid

High yielding and remarkably selective alkylations of a suitably protected derivative of (2S,3aS,7aS)-octahydroindole-2-carboxylic acid are described. The fused bicyclic structure of this proline analogue greatly influences the stereochemical outcome of direct alkylation reactions taking place at the alpha-carbon and provides access to alpha-substituted analogues with retention of the configuration. The overall procedure allows the preparation of enantiopure alpha-substituted derivatives of this Oic isomer, suitably protected for their incorporation into peptides, in a straightforward manner.

Towards the stereoselective synthesis of alpha-methylated (2S,3aS,7aS)-octahydroindole-2-carboxylic acid

A high yielding and remarkably stereoselective alpha-methylation reaction of the (2S,3aS,7aS) stereoisomer of octahydroindole-2-carboxylic acid, (S,S,S)-Oic, suitably protected is described. The severe steric hindrance imposed by the fused cyclohexane ring, which prevents the application of Seebach's self-reproduction of chirality methodology, accounts for the formation of (S,S,S)-(alphaMe)Oic with high selectivity and retention of configuration.