New syntheses of d-tagatose and of 1,5-anhydro- d-tagatose from d-galactose derivatives

3,4- O-Isopropylidene- d- lyxo-hexopyranosid-2-ulose derivatives, obtained by oxidation of 3,4,6-protected d-galactopyranosides, can be alkylated in their anionic 2,6-pyranose forms to produce bis-glycosides containing the 2,5-dioxabicyclo[2.2.2]octane ring system. The 1-benzyl-2-methyl bis-glycosid...

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Published in:	Carbohydrate research Vol. 274; pp. 197 - 208
Main Authors:	Barili, Pier Luigi, Berti, Giancarlo, Catelani, Giorgio, D'Andrea, Felicia, Miarelli, Lucia
Format:	Journal Article
Language:	English
Published:	Netherlands Elsevier Ltd 08-09-1995
Subjects:	1,5-Anhydro- d-tagatose 2,5-Dioxabicyclo[2.2.2]octane Acetals - chemical synthesis d-Tagatose Galactose - analogs & derivatives Galactose - chemistry Galactosides - chemistry Hexoses - chemical synthesis Hexoses - chemistry Magnetic Resonance Spectroscopy Molecular Structure Sugar Alcohols - chemistry Sugar Alcohols - standards β- d-Tagatopyranoside β- d-Tagatopyranoside d-Tagatose 1,5-Anhydro- d-tagatose 2,5-Dioxabicyclo[2.2.2]octane
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Summary:	3,4- O-Isopropylidene- d- lyxo-hexopyranosid-2-ulose derivatives, obtained by oxidation of 3,4,6-protected d-galactopyranosides, can be alkylated in their anionic 2,6-pyranose forms to produce bis-glycosides containing the 2,5-dioxabicyclo[2.2.2]octane ring system. The 1-benzyl-2-methyl bis-glycoside 4b, when subjected to catalytic hydrogenolysis, produces the methyl d- lyxo-hexopyranos-2-uloside 10, existing as an 8:2 mixture of 1,5-pyranose anomers 9. Computational and NMR evidence is presented in favour of the hypothesis that the major anomer has the α configuration. Reduction of 9/10 with NaBH 4 gives methyl 3,4- O-isopropylidene-β- d-tagatopyranoside, that can be hydrolyzed to d-tagatose. A simple synthesis of 1,5-anhydro- d-tagatose, starting from 1,5-anhydro- d-galactitol, is also presented. All new compounds were fully characterized by elemental analysis and by 1H and 13C NMR spectroscopy.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0008-6215 1873-426X
DOI:	10.1016/0008-6215(95)00125-D