!voie A jvoieB 1 Pyridine,SO 3 1) DMF-SO, 1. TMSCI, (C.Hs)N 2) l<:!HPO,e H 1 2.CISQ:PTMS 3.KHPO, Cbz-Np ,.CH3 .•' N o 'so, HSO, HSO,-