The oxazolidinone obtained from Fmoc-Asp-OH, paraformaldehyde and TosOH as catalyst has been converted into Dap derivatives, β-diazomethyl ketones, N-glycosylated Asn, and N'-glycosylated Dap Nβ-ureas. Heating in acetanhydride yields the cyclic anhydride which could be converted rather regioselectively into the β-anilide with o-anisidine and into N-glycosylated Asn with protected glycosylamines in DMSO.