The effect of double-bond geometry on the crystallographic conformations of two enopyranuronates

✍ Scribed by John C. Barnes; John S. Brimacombe; Derek J. Irvine

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 767 KB
• Volume: 200
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(90)84183-u

✦ Synopsis

In the crystal structure of methyl (Z)-8,9-dideoxy-l,2:3,4:6,7-tri-0-isopropylidene-a-~-fhreo-ogalacto-dec-8-enopyranuronate (lo), the allylic system adopts an eclipsed conformation with the smallest group, H-7, at the adjacent stereocentre eclipsing the olefinic double bond. The allylic system of methyl (Q-6-0-benzyl-7,8-dideoxy-l,2:3,4-di-O-isopropylidene-a-D-glycero-D-galcto-non-7-enopyranuronate (11) also adopts an eclipsed conformation in the crystal, but with the benzyloxy group at the adjacent stereocentre eclipsing the olefinic double bond. These ground-state conformations in the solid state provide some insight into the vastly different facial stereoselectivitk of 10 and 11 towards catalytic osmylation.