A Stereodivergent Approach to 5a-Carba-α-D-gluco-, -α-D-galacto and -β-L-gulopyranose Pentaacetates from D-Mannose, Based on 6-exo-dig Radical Cyclization and Barton−McCombie Radical Deoxygenation

The three carbasugars, 5a‐carba‐α‐D‐gluco‐, ‐α‐D‐galacto and ‐β‐L‐gulopyranose pentaacetates 42, 35 and 28 respectively, have been prepared in a stereodivergent manner from D‐mannose. Alkynyl derivatives of 2,3:4,6‐di‐O‐isopropylidene‐D‐mannopyranose, which are homologated at C‐1 by reaction with tr...

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Bibliographic Details
Published in:European journal of organic chemistry 2004-04, Vol.2004 (8), p.1830-1840
Main Authors: Gómez, Ana M., Moreno, Eduardo, Valverde, Serafín, López, J. Cristóbal
Format: Article
Language:English
Subjects:
Carbohydrates
D-Mannose
Radical cyclization
Radical deoxygenation
Synthesis design
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Summary:The three carbasugars, 5a‐carba‐α‐D‐gluco‐, ‐α‐D‐galacto and ‐β‐L‐gulopyranose pentaacetates 42, 35 and 28 respectively, have been prepared in a stereodivergent manner from D‐mannose. Alkynyl derivatives of 2,3:4,6‐di‐O‐isopropylidene‐D‐mannopyranose, which are homologated at C‐1 by reaction with trimethylsilylacetylide, undergo a 6‐exo‐dig radical cyclization, from a radical located at C‐5, to yield a mixture of highly functionalized exo‐methylenecyclohexanes. Ozonolysis of the exocyclic double bond in the latter generated cyclohexanones which, upon stereoselective reduction of the carbonyl moiety followed by site‐selective deoxygenation either at position C‐4 or C‐5a (parent carbohydrate numbering), afforded the title carbasugars. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.200300339