Highly diastereoselective Michael addition of alpha-hydroxy acid derivatives and enantioselective synthesis of (+)-crobarbatic acid.
[reaction: see text]. Michael addition of enolates of 2a and 2b to alpha,beta-unsaturated esters took place selectively on different faces (Si and Re, respectively) of the double bond to give the corresponding products 4 and 5, respectively, with >98% de. Subsequent hydrolysis of these Micheal adducts gives 3,4-disubstituted gamma-lactones with high enantiomeric excesses.
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300, Republic of China.
D P
DP
Jang
J W
JW
Chang
B J
BJ
Uang