Spiroketal Synthesis. — A Case of Intramolecular Glycoside Bond Formation

✍ Scribed by Preuss, Rainer ;Jung, Karl-Heinz ;Schmidt, Richard R.

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 678 KB
• Volume: 1992
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199219920166

✦ Synopsis

Abstract

From 4‐O‐unsubstituted glucose derivatives 1a, b the 4‐hydroxymethyl‐substituted glucose derivatives 9a, b were obtained via oxidation to the ketone, Wittig reaction with methylenetriphenylphosphorane, borane addition, and subsequent oxidation to yield the diastereomeric galactose‐derived compounds 5a, b; the required inversion of configuration at C‐4 was accomplished through oxidation to the formyl derivatives, base‐catalyzed isomerisation, and then reduction. Transformation of hydroxymethyl derivatives 9a, b into the iodo derivatives 11a, b and reaction with n‐butyllithium generated the C‐lithiated species 11aA, bA which furnished with O‐benzyl‐protected gluconolactone 12 the ketose derivatives 13a, b. Treatment with Et~2~O–BF~3~ afforded under concomitant 6‐O‐debenzylation the spiroketals 15a, b. Hydrogenolytic O‐debenzylation and subsequent O‐acetylation led to compounds 16a and 16b, respectively. The anomeric ketoside configuration was derived from NOE experiments.