A stereoselective synthesis of anti-gamma,delta-alkynyl- and -alkenyl-beta-hydroxy-alpha-amino esters from tin(II) enolates of glycinate.

Condensations between the tin(II) enolate 11 of ethyl N-tosylglycinate and conjugated ynals 12 and ynones 14 are highly diastereoselective, in favour of the anti-isomers 13 and 15; similar reactions of enals and enones 17 show lower but still useful levels of anti-stereoselectivity.