K. Pachler, E. Rathbone, G. R. Woolard
Feb 1, 1980
Citations
0
Influential Citations
7
Citations
Journal
Carbohydrate Research
Abstract
Abstract The pyranoid conformations of 7-acetamido-6,7,8-trideoxy-1,2:3,4-di- O -isopropylidene- d - glycero -α- d - galacto -octopyranose ( 3 ) and 7-acetamido-7,8-dideoxy-1,2:3,4-di- O -isopropylidene- l - threo -α- d - galacto -octopyranose ( 4 ) in solution have been determined by calculation of the dihedral angles from the vicinal, proton-proton coupling-constants, using three modifications of the Karplus equation. Of these, only the equation 3 J (HCCH)(φ) (7.48 0.74 -ΣδE x ) (2.03 0.17 ΣE x )cos φ + (4.60 0.23 ΣδE x )cos 2φ + 0.06 (Σ ± ΔE x )sin φ + 0.62 (Σ ± ΔE x )sin 2φ indicates that the pyranoid part of 3 and 4 has the ° S 2 conformation, very slightly distorted towards ° H 5 , in agreement with the conformations determined for the crystalline state. Analysis of the 1 H-n.m.r. data for a series of 1,2:3,4-di- O -isopropyl-idene-α- d - galacto -octopyranose derivatives shows that the pyranoid parts of these compounds adopt the same conformation as that found for 3 and 4 .