Nonracemizable isocyanoacetates for multicomponent reactions.

Chiral ortho esters of alpha-isocyano acids were synthesized from commercially available Cbz-protected alpha-amino acids. These compounds are stable toward racemization in the Ugi 4CC in contrast to known esters of alpha-isocyano acids. Applying them in Ugi 4CC with subsequent deprotection gives access to dipeptides with preserved configuration at the C-terminal amino acid.