First syntheses of D-mannose penta- and decasaccharides, the repeating unit and its dimer of the cell-wall mannan of Candida kefyr IFO 0586

alpha-D-Mannopyranosyl-(1-->2)-alpha-D-mannopyranosyl-(1-->6)-[alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranosyl-(1-->2)]-alpha-D-mannopyranose and alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranosyl-(1-->6)-[alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranosyl-(1-->2)]-alpha-D-mannopyranosyl-(1-->6)-[alpha-D-mannopyranosyl-(1-->2)]-alpha-D-marmopyranosyl-(1-->6)-[alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranosyl-(1-->2)]-alpha-D-mannopyranose, the repeating unit and its dimer of the cell wall mannan of the pathogenic yeast Candida kefyr IFO 0586, have been efficiently synthesized via their allyl glycosides by using allyl 3,4,6-tri-O-benzoyl-alpha-D-mannopyranoside, allyl 6-O-acetyl-3,4-di-O-benzoyl-alpha-D-mannopyranoside, and allyl 3,4-di-O-benzoyl-alpha-D-mannopyranoside as synthons. The blocked pentasaccharide was regio- and stereoselectively prepared by coupling of allyl 3,4-di-O-benzoyl-alpha-D-mannopyranoside with 2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-6-O-acetyl-3,4-di-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate, and then with 2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate in a one-pot manner. (C) 2003 Elsevier Science Ltd. All rights reserved