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 A15; similar reactions of enals and enones 17 show lower but still useful levels of anti-Astereoselectivity.