Silver-Promoted Direct Phosphorylation of Bulky C(sp2)-H Bond to Build Fully Substituted β-Phosphonodehydroamino Acids

A general and practical cross-dehydrogenative coupling protocol between readily available trisubstituted alpha,beta-dehydro alpha-amino carboxylic esters and H-phosphites is described. This C(sp(2))-H phosphorylation reaction proceeds with absolute Z-selectivity promoted by silver salt in a radical relay manner. The bulky tetrasubstituted beta-phosphonodehydroamino acids were obtained in grams and added new modules to the toolkit for peptide modifications.