Stereospecific synthesis of N-[Bis(methylthio)methylene]-α,β- didehydroamino acid methyl esters, new synthons in the synthesis of α-amino acids

Abstract

N-[Bis(methylthio)methylene]-α,β-didehydroamino acid methyl esters 4a–c have been prepared with total geometric selectivity from easily accesible β-hydroxyamino acids through N-[bis(methylthio)methylene]-β-hydroxyamino acid methyl esters 3a–c as intermediates. The (E)-isomers can be easily converted into the corresponding (Z)-isomers in the presence of a catalytic amount of titanium (IV) chloride.