“Customizable” Units in Di- and Tripeptides: Selective Conversion into Substituted Dehydroamino Acids

The selective conversion of serine or threonine units of di- and tripeptides into substituted dehydroamino acids is reported. Thus, these common α-amino acids undergo a scission–phosphorylation process to give α-amino phosphonate residues. A Horner–Wadsworth–Emmons reaction with aldehydes or ketones follows to afford the final products with excellent Z-stereoselectivity (Z:E > 98:2). In this way, a single peptide precursor can selectively be transformed into a variety of derivatives.