Rotation, hindered, of acetyl group

Aldofuranoses, 4-acetamido-4-deoxy-, hindered rotations of acetyl groups, 196, 197... 

Hindered Rotation of the Acetyl Group in Monosaccharides Containing an Acetamido Croup in the Ring... 

At about 50°, the hindered rotation of the amide group in the six-membered-ring amide is no longer observable, and only two rotamers remain as a result of the hindered five-membered-ring amide in the 1,6-anhydro ring (cis t 4.01, trans t 4.19). At 96°, the rotation of this amide group also is so rapid that only one signal appears for the ano-meric proton at t 4.10, and one for the N-acetyl methyl protons at t7.80. 

Abequose, 272 Abequoside, methyl fi-, 272 Acetolysis, of cyclic monosaccharides, ring contraction in, 187 Acetyl group, hindered rotation of, in monosaccharides, 193, 197 Acetylimino group, monosaccharides containing, 166... 

Rotation, hindered, of acetyl group in monosaccharides, 193,197 Ruthenium tetraoxide, for oxidation of carbohydrate sulfonic esters, 258... 

Chiral imidazoUdin-2-thione or 2-one were prepared from o-glucoseamine by reaction with o,o -disubstituted arylisothiocyanates to give 39 which can be cycHzed to 40 [76]. Thus, a variety of derivatives were prepared carrying different aryl groups and as a consequence of hindered rotation, some of them exist as stable rotamers (Fig. 7). Treatment of 39 with acetic anhydride in pyridine at low temperature gave the respective per-O-acetyl derivative imidazolidine thione, which upon elimination of acetic acid gave the imidazoline thion 41 as a mixture of atropisomers [76]. 

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