Crystal And Molecular Structure Of Methyl L-Glycero-Alpha-D-Manno-Heptopyranoside, And Synthesis Of 1 -> 7 Linked L-Glycero-D-Manno-Heptobiose And Its Methyl Alpha-Glycoside

Methyl L-glycero-alpha-D-manno-heptopyranoside was synthesized in good yield by a Fischer-type glycosylation of the heptopyranose with methanol in the presence of cation-exchange resin under reflux and microwave conditions, respectively. The compound crystallized from 2-propanol in an orthorhombic lattice of space group P2(1)2(1)2 showing a comparatively porous structure with a 2-dimensional O-H center dot center dot center dot O hydrogen bond network. As model compounds for the side chain domains of the inner core structure of bacterial lipopolysaccharide, L-glycero-alpha-D-manno-heptopyranosyl-(1 -> 7)-L-glycero-D-manno-heptopyranose and the corresponding disaccharide methyl alpha-glycoside were prepared. The former compound was generated via glycosylation of a benzyl 5,6-dideoxy-hept-5-enofuranoside intermediate followed by catalytic osmylation and deprotection. The latter disaccharide was efficiently synthesized in good yield by a straightforward coupling of an acetylated N-phenyltrifluoroacetimidate heptopyranosyl donor to a methyl 2,3,4,6-tetra-O-acetyl heptopyranoside acceptor derivative followed by Zemplen deacetylation. (C) 2011 Elsevier Ltd. All rights reserved.