Synthesis of chitotetraose and chitohexaose based on dimethylmaleoyl protection

tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta -D -glucopyranoside was readily transformed into the disaccharide glycosyl don or, 3,4,6-tri-O-acetyl-2-deoxy-2-dimethylmaleimido-beta -D-glucopyranosyl-( 1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-alpha/beta -D-glucopyr anosyl trichloroacetimidate, and the disaccharide glycosyl acceptor, tert-b utyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta -D-gluco pyranosyl-(1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta -D-glu copyranoside. A TMSOTf-catalysed coupling of the acceptor with the donor af forded the respective tetrasaccharide derivative, which can be transformed to chitotetraose. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-dimethy lmaleimido-4-O-phenoxyacetyl-beta -D-glucopyranosyl-(1 --> 4)-3,6-di-O-benz yl-2-deoxy-2-dimethylmaleimido-beta -D-glucopyranoside was converted into d onor 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-4-O-phenoxyacetyl-beta -D- glucopyranosyl- (1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-beta -D-glucopyranosyl trichloroacetimidate. Its coupling with benzyl 3,6-di-O-b enzyl-2-deoxy-2-dimethylmaleimido- beta -D-glucopyranosyl-(1 --> 4)-3,6-di- O-benzyl-2-deoxy-2-dimethylmaleimido-beta -D-glucopyranoside, followed by d ephenoxyacetylation, gave benzyl 3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimii do-beta -D-glucopyranosyl- (1 --> 4)-3,6-di-O-benzyl-2-deoxy-2-dimethyimale imido-beta -D-glucopyranosyl-(1 --> 4)- 3,6-di-O-benzyl-2-deoxy-2-dimethylm aleimido- beta -D-glucopyranosyl-(1 --> 4)-3.6-di-O-benzyl-2-deoxy-2-dimeth ylmaleimido-beta -D-glucopyranoside, whose glycosylation furnished, after r eplacement of the DMM-group by the acetyl moiety and subsequent deprotectio n, chitohexaose. (C) 2001 Elsevier Science Ltd. All rights reserved.