A new approach to the synthesis of di- and tripeptides with unnatural amino acids using organozinc chemistry

Di- and tripeptides which incorporate an iodoalanine unit at the C-terminus can be converted into the corresponding organozinc reagents upon treatment with activated zinc. These C-terminal di-and tripeptide organozinc reagents react with electrophiles either under palladium catalysis, or by prior transmetallation to a zinc/copper reagent, to give di-and tripeptides incorporating non-proteinogenic amino acids without loss of stereochemical purity. (C) 1997 Elsevier Science Ltd.