Diphenylsilydiethylene- (DPSide-) group has been developed as a new primary amine protecting group. The new protecting group exhibits novel orthogonality against other commonly used amine-protecting groups and excellent chemoselectivity for unbranched a-amino acid esters. Removal of this protecting group was effected under mild fluoride-based cleavage conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.