Preparation of 4,6-cyclo-hexopyranoses by palladium-mediated intramolecular cyclodehalogenation.
4,6-Cyclo-4,6-dideoxy-hexapyronoses were obtained by palladium-mediated intramolecular cyclodehalogenation. Thus, methyl 2,3-di-O-acetyl-4,6-dideoxy-4,6-diiodo-beta-D-galactopyranoside (3) afforded methyl 2,3-di-O-acetyl-4,5-cyclo-4,6-dideoxy-beta-D-galactopyranoside (5) in 56% yield upon treatment with hydrogen in the presence of palladium-on-charcoal and diethylamine. The structure of 5 was proven by MS, NMR including NOE measurements, and by independent conversion of 4 to 5 by zinc-mediated Wurtz synthesis. Similarly, methyl 2,3-di-O-acetyl-4,6-cyclo-4,6-dideoxy-alpha-D-galactopyranoside (6) and O-(2,3,-di-O-acetyl-4,6-cyclo-4,6-dideoxy-alpha-D-galactopyranosyl)-(1-- >4)-1,2,3,6-tetra-O-acetyl-beta-D-glucopyranose (17) were obtained along with the respective 4,6-dideoxy analogues. Also methyl 2,3-di-O-acetyl-4,6-dideoxy-4,6-diiodo-beta-D-glucopyranoside (19) gave galacto-configured 5 stereoselectively.
Wessel
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HP
F. Hoffmann-La Roche Ltd., Pharma Division, Basel, Switzerland.
Viaud
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Gardon
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D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D003837:Deoxy Sugars / Q000138:chemical synthesis*; D004187:Disaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D006601:Hexoses / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009904:Optical Rotation; D010165:Palladium
D003837:Deoxy Sugars; D004187:Disaccharides; D006601:Hexoses; D007202:Indicators and Reagents; D010165:Palladium