title: Studies related to carba-pyranoses: a radical decarboxylation approach to monocarba-disaccharides.
abstract: (1--> 1), (1--> 3) and (1--> 4) acetal-linked monocarba-disaccharides have been synthesised from a series of glucosylated gamma- and delta-lactonic acids prepared from common intermediate, obtained from the Diels-Alder reaction of maleic anhydride and (E)-1-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyloxy)-3-(trimethylsiloxy)buta-1,3-diene 1. Thiohydroxamic ester 14, prepared from gamma-lactonic acid 9, gave, upon treatment with tert-butyl thiol and light, the lactone 15. Subsequent lithium aluminium hydride reduction and acetylation gave the (1--> 3) acetal-linked monocarbadisaccharides 1,6-di-O-acetyl-3-O-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyl)-2,4-dideoxy-5a-carba-beta-L-threo-hexopyranose 16. In a similar manner, protected monocarba-disaccharides 13, 19, 30, and 35 possessing L-ido, L-xylo, D-arabino and L-ido configurations of the carba-pyranose ring have been prepared. Treatment of thiohydroxamic esters 14 and 17 with either tert-butyl thiol or trityl thiol, dimethyl sulfide, oxygen and light gave alcohols 20 and 22. Subsequent lithium aluminium hydride reduction and aceytlation gave the monocarbadisaccharides 1,4,6-tri-O-acetyl-3-O-[2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyl]-2-deoxy-5a-carba-beta-L-arabino-hexopyranose 21 and 1,2,4,6-tetra-O-acetyl-3-O-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyl)-5a-carba-beta-L-glucopyranose 23 respectively.
authors.affiliation: Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand. dlarsen@alkali.otago.ac.nz
authors.forename: David S
authors.initials: DS
authors.lastname: Larsen
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Lins
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Stoodley
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Trotter
mesh_terms: D000080:Acetals / Q000737:chemistry; D003653:Decarboxylation; D004187:Disaccharides / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure
chemical_list: D000080:Acetals; D004187:Disaccharides