Asymmetric Synthesis of Proline Derivatives from (2R) and (2S)-2-tert-Butyl-3-Benzoyl-4-Methyleneoxazolidin-5-one
The conjugate addition of enamines (2a,b) to the chiral oxazolidinones (1) or ent-(1) favours cis 2,4-substituted oxazolidinone adducts while trans 2,4-substituted oxazolidinone adducts are favoured from the addition reactions of enamine (2c).The diastereomeric adducts from the addition of (2a) to (1) are readily separated and can be converted to (5R,2S) and (5S,2R) 5-iso-propyl proline efficiently and in good overall yield.The extenstion of this protocol to the synthesis of perhydroindole carboxylic acid suffered from poor overall stereochemical control.
Pyne, Stephen G.,Javidan, Abdollah,Skelton, Brian W.,White, Allan H.
Short enantioselective syntheses of trans-5-alkylprolines from new functionalized amino alcohols
(Chemical Equation Presented) Amino alcohols, having an enol ether function, cyclized in acidic medium to give quantitatively diastereosomerically pure bicyclic compounds that were transformed in five steps in enantiopure trans-5-alkylproline derivatives.