Synthesis of chitotetraose and chitohexaose based on dimethylmaleoyl protection Original Research Article

tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranoside was readily transformed into the disaccharide glycosyl donor, 3,4,6-tri-O-acetyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-α/β-d-glucopyranosyl trichloroacetimidate, and the disaccharide glycosyl acceptor, tert-butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranoside. A TMSOTf-catalysed coupling of the acceptor with the donor afforded the respective tetrasaccharide derivative, which can be transformed to chitotetraose. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-4-O-phenoxyacetyl-β-d-glucopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranoside was converted into donor 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-4-O-phenoxyacetyl-β-d-glucopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranosyl trichloroacetimidate. Its coupling with benzyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranoside, followed by dephenoxyacetylation, gave benzyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-d-glucopyranoside, whose glycosylation furnished, after replacement of the DMM-group by the acetyl moiety and subsequent deprotection, chitohexaose.