selective aldol reaction mediated by boron compounds and a mild organic base (DBU) was developed. Inclusion of electron-withdrawing groups in the amino acid derivative ligands reacted with BH3·SMe2 forms a boron promoter with increased Lewis acidity at the boron atom and facilitated the carboxylic acid selective enolate formation, even in the presence of other carbonyl groups such as amides, esters, ketones
Stereoselective reduction of β-keto esters with zinc borohydride. stereoselective synthesis of -3-hydroxy-2-alkylpropionates
作者:Tadashi Nakata、Takeshi Oishi
DOI:10.1016/s0040-4039(00)77774-4
日期:1980.1
-3-hydroxy-2-alkylpropionates were prepared in high stereoselectivity and in high isolated yield by zincborohydridereduction of the corresponding β-keto esters.
A convenient and general, reagent-controlled, diastereo- and enantioselective aldol reaction of diisopinocampheylboron enolates of esters, followed by reduction, has been developed as an alternative to crotylboration-ozonolysis. This protocol was then exploited for the double diastereoselective synthesis of the C11-C17 subunit of (-)-dictyostatin.
ABEN R. W.; SCHEEREN J. W., SYNTHESIS, 1978, NO 5, 400-402