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A concise approach to the synthesis of the unique N-mannosyl d-β-hydroxyenduracididine moiety in the mannopeptimycin series of natural products.

The asymmetric synthesis of the orthogonally protected N-mannosyl d-β-hydroxyenduracididine (N-Man-d-βhEnd) is described, starting from enantiopure silylated (S)-serinol. The key steps are: (i) glycosylamine formation between protected serinol and a benzylated d-mannose; (ii) guanidinylation; and (iii) cyclic guanidine formation. This synthesis constitutes a breakthrough in our studies towards a total synthesis of mannopeptimycin and should also allow for other studies in the field of mannopeptimycin research, including the synthesis of derivatives.