Abstract : A series of peptides containing one or two hydroxamate groups were synthesized, the key step being the selective N-acylation of terminal N-hydroxy-dipeptides. The oxygen atom of the hydroxyl group can serve to graft another chain; it thus gives access to new pseudopeptides. On the one hand, the acylation of N-hydroxy-peptides was performed under a variety of conditions allowing the introduction of a range of groups, including amino acids. Elongation of these N-acyloxy-peptides is possible in all directions, even if interesting rearrangements may occur in some cases. On the other hand, alkylation reactions using Mitsunobu conditions led to the synthesis of N-allyloxy- and N-homoallyloxy-tripeptides and of a bis-unsaturated hexapeptide which can be cyclized through metathesis.