Chemistry. 1996 May;2(5):502-510. doi: 10.1002/chem.19960020508.

C-Disaccharides of Ketoses.

Chemistry (Weinheim an der Bergstrasse, Germany)

Hansjörg Streicher, Armin Geyer, Richard R Schmidt

PMID: 29178224 DOI: 10.1002/chem.19960020508

Abstract

Reaction of gluconolactone 2 with allylmagnesium bromide at low temperatures afforded ketopyranose 3, which could easily be converted into open-chain ketoses (R)-6 and (S)-6. Their reaction with lithioacetylide 9 afforded propargylic alcohol derivatives (R)-10 and (S)-10, which could not be cyclized directly to the desired C-ketosides. They were converted by standard procedures into (R)-14 and (S)-14 and then into dicobalthexacarbonyl complexes (R)-16 and (S)-16. A facile acid-catalyzed ring closure gave the desired C-ketosides (R)-18 α/β and (S)-18α/β, respectively, in different ratios. In order to demonstrate that removal of the protective groups and hydrogenation of the CC triple bond proceed smoothly, (R)-18 α was transformed into the deprotected target molecule (R)-1 α. For the assignment of the new chiral centers at C-2/2' and at C-8, (S)-18α was transformed into azido derivative (S)-22α, which underwent intramolecular cycloaddition to afford the spiro derivative (S)-25α. Because of the conformational constraints in this molecule, unequivocal configurational assignment was possible with the help of NMR data.

Copyright © 1996 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Keywords: C-glycosides; alkynes; cobalt complexes; cyclizations; enzyme inhibitors

Publication Types

• Journal Article