Studies on the 6-homologation of β-D-idopyranosides. (5th June 2017)

• Record Type: Journal Article
• Authors: Hevey, Rachel; Ling, Chang-Chun
• Is Part Of: Carbohydrate research. Volume 445(2017)
• Page Start: 65
• Page End: 74
• Publication Date: 2017-06-05
• Subjects: Idopyranoside -- 6-Homologation -- 4, 6-O-benzylidene -- Reductive opening -- O-benzyl ether -- Heptopyranosides; Carbohydrates -- Periodicals; Chemistry, Organic -- Periodicals; Biochemistry -- Periodicals; Carbohydrates -- Periodicals; Chimie organique -- Périodiques; Glucides -- Périodiques; Biochemistry; Carbohydrates; Chemistry, Organic; Periodicals; Electronic journals; 507.78
• DOI: 10.1016/j.carres.2017.04.007
• Languages: English
• ISSNs: 0008-6215

Abstract

Abstract: β-D-Idopyranosides are interesting sugars because of their unusual conformational flexibility in the pyranosyl ring, and also their β-1, 2- cis -anomeric configuration. Here we report our studies of the regioselective opening of 4, 6- O -benzylidene-protected β-D-idopyranosides under reducing conditions, and the subsequent 6-homologation via Swern oxidation and Wittig olefination to afford a 6, 7-dideoxy-β-D- ido -hept-6-enopyranoside. This olefination product was found to adopt predominantly 1 C4 conformation in solution by NMR experiments, which places the vinyl group at a more sterically hindered axial position and creates difficulty in subsequent hydroborations. Graphical abstract: Highlights: Reductive opening of 4, 6- O -benzylidene acetals of β-D-idopyranosides has been studied. DIBAL-H/toluene and borane/TMSOTf/dichloromethane give different regioselectivities. 6-Homologation was successful via Wittig olefination with a sterically unhindered ylide. β-D-Idopyranosides were found to adopt different conformations depending on the substitution patterns. Intramolecular H-bonding likely plays a role in stabilizing ring conformations of β-D-idopyranosides.