SYNTHESIS, CRYSTAL-STRUCTURE, AND CONFORMATION OF METHYL 2,3-O-ISOPROPYLIDENE-ALPHA-D-MANNO-HEPTOFURANOSIDE

Methyl 2,3-O-isopropylidene-alpha-D-manno-heptofuranoside (9) has been synthesised from the acetyliron complex 2 by a sequence of reactions involving deprotonation of 2, its reaction with aldehyde 5, decomplexa tion, isolation of 7, and reduction to 9. Compound 9 crystallises in t he orthorhombic system, space group P2(1)2(1)2(1), with cell dimension s: a = 6.097(1), b = 7.942(1), c = 26.862(3) Angstrom. The intensity d ata were collected with a Syntex P2(1) diffractometer. The structure w as served by direct methods and refined by the full-matrix, least-squa res procedure, resulting in R = 0.049. The furanoside and 2,3-O-isopro pylidene rings are characterised by envelope conformations (5)E and E( 3), respectively. Relatively strong intermolecular hydrogen bonds were observed in the crystal structure.