Stereoselective reduction of various alpha-keto esters 5a-d derived from exo-10,10-diphenyl-2,10-camphanediol 4a and exo-10,10-diphenyl-10-methoxy-2-camphanol 4b is described. High to excellent diastereomeric excess (99% de) with good chemical yields is obtained. The sense of stereoselectivity as a function of C10 modification is remarkable. Further, in the case of 5d, both diastereomers of a-hydroxyl esters can be obtained with excellent optical purity by the appropriate choice of reaction conditions. The influence of the solvents and additives on the reaction course has been investigated.
Synthesis of a Camphor-Derived Auxiliary and the Application to the Asymmetric Darzens Reaction
作者:Yamu Xia、Haixin Liu、Xiaoli Dai
DOI:10.3184/174751913x13737254410429
日期:2013.9
A readily available chiral camphor-derived auxiliary was synthesised through a highly efficient and short general route. The Darzensreaction of the auxiliary with aldehydes in the presence of base gave glycidic esters with almost complete diastereocontrol and high yield.