Asymmetric Synthesis of Chiral 1,3-Dimethyl Units Through a Double Michael Reaction of Nitromethane and Crotonaldehyde Catalyzed by Diphenylprolinol Silyl Ether

Abstract

An efficient synthetic route to install chiral 1,3-dimethyl units through a double Michael reaction of crotonaldehyde and nitromethane catalyzed by diphenylprolinol silyl ether is developed. Either 1,3- syn - or 1,3- anti -dimethyl units are obtained selectively depending on the enantiomer of the diphenylprolinol silyl ether catalyst used. The side chain of pneumocandin B 0 is synthesized enantioselectively by using the present method as a key step.