Efficient parallel resolution of an active ester of 2-phenylpropionic acid using quasi-enantiomeric Evans’ oxazolidinones

Catalytic parallel kinetic resolution under homogeneous conditions

Two complementary chiral catalysts, the phosphine 8d and the DMAP-derived ent-23b, are used simultaneously to selectively activate a mixture of two different achiral anhydrides as acyl donors under homogeneous conditions. The resulting activated intermediates 25 and 26 react with the racemic benzylic alcohol 5 to form enantioenriched esters (R)-24 and (S)-17 by fully catalytic parallel kinetic resolution (PKR). The aroyl ester (R)-24 is obtained with near-ideal enantioselectivity for the PKR process, but (S)-17 is contaminated by ca. 8% of the minor enantiomer (R)-17 resulting from a second pathway via formation of mixed anhydride 27 and its activation by 8d.

Synthesis of enantiomerically pure isotopomers of 2-phenylpropionic acids

A series of enantiomerically pure [D,(13)C]-labeled isotopomeric 2-phenylpropionic acids were efficiently synthesized using a diastereoselective alkylation and kinetic resolution strategy.

Mutual kinetic separation of isotopomers of pentafluorophenyl 2-phenyl propionate using quasi-enantiomeric oxazolidinones

Mutual separation of an equimolar mixture of quasi-enantiomeric [D,13C]-labeled isotopomers of pentafluorophenyl 2-phenylpropionate can be achieved efficiently by use of two quasi-enantiomeric Evans' oxazolidinones. The levels of stereocontrol were high, leading to products with predictable configurations.

Parallel kinetic resolution of an oxazolidinone using aquasi-enantiomeric combination of [D,13C]-isotopomers of pentafluorophenyl 2-phenyl propionate

Parallel kinetic resolution of Evans' phenylglycine derived oxazolidinone using an equimolar combination of quasi-enantiomeric active esters (derived from [D,13C]-labeled 2-phenylpropionic acid) was achieved. The levels of stereocontrol were high, leading to products with predictable configurations.

Synthesis of Cyclopropene α-Amino Acids via Enantioselective Desymmetrization

[reaction: see text] The preparation of cyclopropene alpha-amino acids via the enantioselective desymmetrization of cyclopropene bis-carboxylic acid derivatives is described. The amino acids are stable to harsh reaction conditions, and a derivative has been incorporated into a tripeptide using conventional methods for peptide synthesis.