Hydrazinolysis of Dde group is troublesome in the presence of Aloc protected peptides. We elucidate that reduction of the Aloc double bond occurs both in solution and on solid support preventing the subsequent Aloc deprotection and resulting in mixtures difficult to purify. We report here that addition of allyl alcohol as scavenger circumvents this side reaction and provides a complete orthogonality between Dde and Aloc in solution and solid phase peptide synthesis. (C) 1998 Elsevier Science Ltd. All rights reserved.