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O ‐Benzoyl side‐chain conformations in 2,3,4,6‐tetra‐ O ‐benzoyl‐β‐ d ‐galactopyranosyl‐(1→4)‐1,2,6‐tri‐ O ‐benzoyl‐β‐ d ‐glucopyranose (ethyl acetate solvate) and 1,2,4,6‐tetra‐ O ‐benzoyl‐β‐ d ‐glucopyranose (acetone solvate)
Author(s) -
Turney Toby,
Pan Qingfeng,
Zhang Wenhui,
Oliver Allen G.,
Serianni Anthony S.
Publication year - 2019
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229619000822
Subject(s) - chemistry , bond length , tetra , molecular geometry , double bond , stereochemistry , dihedral angle , d glucopyranose , crystallography , side chain , medicinal chemistry , crystal structure , hydrogen bond , molecule , polymer chemistry , organic chemistry , polymer
The crystal structures of 2,3,4,6‐tetra‐ O ‐benzoyl‐β‐ d ‐galactopyranosyl‐(1→4)‐1,2,6‐tri‐ O ‐benzoyl‐β‐ d ‐glucopyranose ethyl acetate hemisolvate, C 61 H 50 O 18 ·0.5C 4 H 8 O 2 , and 1,2,4,6‐tetra‐ O ‐benzoyl‐β‐ d ‐glucopyranose acetone monosolvate, C 34 H 28 O 10 ·C 3 H 6 O, were determined and compared to those of methyl β‐ d ‐galactopyranosyl‐(1→4)‐β‐ d ‐glucopyranoside (methyl β‐lactoside) and methyl β‐ d ‐glucopyranoside hemihydrate, C 7 H 14 O 6 ·0.5H 2 O, to evaluate the effects of O ‐benzoylation on bond lengths, bond angles and torsion angles. In general, O ‐benzoylation exerts little effect on exo‐ and endocyclic C—C and endocyclic C—O bond lengths, but exocyclic C—O bonds involved in O ‐benzoylation are lengthened by 0.02–0.04 Å depending on the site of substitution. The conformation of the O ‐benzoyl side‐chains is highly conserved, with the carbonyl O atom either eclipsing the H atom attached to a 2°‐alcoholic C atom or bisecting the H—C—H bond angle of an 1°‐alcoholic C atom. Of the three bonds that determine the side‐chain geometry, the C—O bond involving the alcoholic C atom exhibits greater rotational variability than the remaining C—O and C—C bonds involving the carbonyl C atom. These findings are in good agreement with recent solution NMR studies of the O ‐acetyl side‐chain conformation in saccharides.