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Conformational Behaviour of Azasugars Based on Mannuronic Acid
Author(s) -
van Rijssel Erwin R.,
Janssen Antonius P. A.,
Males Alexandra,
Davies Gideon J.,
van der Marel Gijsbert A.,
Overkleeft Herman S.,
Codée Jeroen D. C.
Publication year - 2017
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.201700080
Subject(s) - chemistry , amide , stereochemistry , ring (chemistry) , cyclohexane conformation , carboxylic acid , oxocarbenium , conformational change , chemical shift , hydrogen bond , organic chemistry , molecule , catalysis , nucleophile
A set of mannuronic‐acid‐based iminosugars, consisting of the C‐5‐carboxylic acid, methyl ester and amide analogues of 1deoxymannorjirimicin (DMJ), was synthesised and their pH‐dependent conformational behaviour was studied. Under acidic conditions the methyl ester and the carboxylic acid adopted an “inverted” 1 C 4 chair conformation as opposed to the “normal” 4 C 1 chair at basic pH. This conformational change is explained in terms of the stereoelectronic effects of the ring substituents and it parallels the behaviour of the mannuronic acid ester oxocarbenium ion. Because of this solution‐phase behaviour, the mannuronic acid ester azasugar was examined as an inhibitor for a Caulobacter GH47 mannosidase that hydrolyses its substrates by way of a reaction itinerary that proceeds through a 3 H 4 transition state. No binding was observed for the mannuronic acid ester azasugar, but sub‐atomic resolution data were obtained for the DMJ ⋅ Ck GH47 complex, showing two conformations— 3 S 1 and 1 C 4 —for the DMJ inhibitor.