Glycofuranosides and Thioglycofuranosides. VII. Crystalline Alkyl Furanosides and Dimethylacetal of d-Mannose

Abstract

The general method of Pacsu and Green2 for the preparation of glycofuranosides from the sugar mercaptals was applied to mannosediethylmercaptal which was previously obtained3 from sirupy mannose by Fischer and from crystalline mannose by Levene and Meyer.4 It was found that this starting material could be prepared conveniently and in good yield directly from the readily available a-methyl-¿-mannopyranoside5 by the action of hydrochloric acid and ethyl mer-

Cellulose Studies

“…If the classical concept of cellulose structure is correct-that is, if only normal methyl glucopyranoside end-groups are presentthen the rate of acid hydrolysis, as measured by the increase in the reducing power, should be of the order of magnitude shown by the normal methyl glucopyranosides. On the other hand, a very fast rate of hydrolysis, which is characteristic for the openchain dimethyl acetals of the sugars [5,10,12], would constitute evidence for the presence of residues of this type; hence, it would favor the new concept of cellulose structure.…”

Anomeric Effect

“…Already in 1929 W.N. Haworth[#] had pointed out that pyranose rings could exist in two chair and four "classical" boat conformations (the flexible boat had not yet been thought of), and in the 30's and 40's other workers [9,70] (particularly Hassel and Ottar[77]) had given reasons to believe most pyranose rings existed in one of the two possible chair conformations.…”

Construction of complex molecular models with application to carbohydrates

“…There are eight strainless forms which can be constructed for any given pyranose sugar ((?). Scattergood and Pacsu (8) give particularly good illustrations of how the eight types of ring appear when formed from the Fisher-Hirschfelder models. The eight forms are based on one "trans" or "chair-shaped" ring and three "cis" or "boat-shaped" rings, each of the four being translatable into two different configurations for a given sugar by numbering the carbon atoms in the two possible directions from the oxygen.…”

“…2. Scattergood and Pacsu (8) cite reasons for eliminating all but one of the eight models for the aldohexoses. The favored model is based on a trans ring form, arguments being grounded largely in the absence of steric hindrance when -OH, -CH2OH, and -H groups are placed at proper locations.…”

“…The particular cis ring used by these investigators is one with carbon atoms 1 and 4 in a plane which is different from that containing the other atoms of the ring. While this configuration was discarded by Scattergood and Pacsu (8), because of slight steric difficulties involving the -OH and -H on carbon atoms 1 and 4, this is perhaps not serious, particularly in view of the possibility of avoiding the difficulty by slight simultaneous atom rotations about ring bonds, as mentioned above. Also, until the repulsive forces used to discard the cis configurations in general are more definitely known, the possibility of the Freudenberg model cannot be disregarded.…”