One-Pot Syntheses of Dissymmetric Diamides Based on the Chemistry of Cyclic Monothioanhydrides. Scope and Limitations and Application to the Synthesis of Glycodipeptides

Opening cyclic monothioanhydrides by amines provides a convenient entry into amido thioacids that can be trapped in situ by 2,4-dinitrobenzenesulfonamides, by electron-deficient azides, or by amines in the presence of Sanger’s reagent leading, in each case, to dissymmetric diamides in what can be considered a one-pot, three-component coupling sequence. The use of monothiomaleic anhydride and bifunctional nucleophiles such as amino thiols provides access to heterocyclic amides. The low reactivity of cyclic monothioanhydrides toward alcohols enables the use of methanol as solvent and obviates the need for the protection of alcohols in the various reaction components. Reaction of N-benzyloxycarbonyl-l-aspartic monothioanhydride with unprotected glycosyl amines, followed by capture of the thioacid intermediate with N-sulfonyl amino acid derivatives results in a three-component convergent synthesis of glycosylated peptides.