No abstract

.IRs'l-RACT The main slime polysaccharide produced by Sacchnrornyces r o z~z i i during the fermentation of D-glucose to D-arabitol is a nlannan. i\cetolysis of the polymer has afforded di-and tri-saccharides in good yield, but 110 higher oligosaccharides \irere produced. T h e disaccharide is shown by methylation and lead tetraacetate oxidation to be 2-O-ol-~-ma11nopyranosp~-~-mannose, establishing the presence of a 1,2-a-1inl;agc in the polysaccharide. On acid hydrolysis the methylated mannan gives mainly 2,3,4,6-tetra-O-methyl-~-1l1a1mose, 3,4,G-tri-0-methyl-Dmannose, and 3,4-di-O-methyI-~-1nannose; lesser components found are 2,4,6-tri-0-methyl-D-mannose and 3-0-111ethyI-~-n1annose. The ~nethylation and acetolysis data together suggest an average structural unit consisting of a main chain of D-mannopyranose units containing alternate 1,2-and 1,G-linlcages, t o which single D-mannopyranose units are attached by 1,2-1inl;ages as side chains; alternatively, 1,2-disaccharide n nits are attached as side chains by 1,2-li11lcages to a l,6-linlced main chain.During the fermentation of D-glucose to D-arabitol by .Sncclzaromyces roz~rii (14) a slime is produced in the cultul-e medium. The slime was isolated from an active culture filtrate by repeated precipitation with ethanol from \\rater as a light brown powder containill:: approximately 15% protein. I t yielded mainly mannose, on acicl hydrolysis, although traces of pentose and another hexose were detected in its h~drolyzate on paper chromatograms. After acetylation, followed by deacetylation of the product, a polysaccharide was obtained which nras v i r t~~a l l y free of protein and contained only mannose. This purified material had [a]* +58", ancl in common with other mannans formed an insoluble copper complex.Partial acetolysis of the polysaccharide gave rise to a mixture ol mono-, di-, and tri-saccharide acetates which, after saponification, \\rere chromatographed 011 charcoal (15) and then 011 cellulose (10). The yields of the di-ancl trisaccharide were 109; and 25%, respectively. The disaccharide fraction was a m o r p h o~~s but appeared, from paper chromatographic examination, to be comprised of a single component. I t yielded a crystalline octa-0-methyl ether, which on hydrolysis gave only crl-stalline 3,4,6-tri-0-methyl-D-mannose (1) and 2,3,~,G-tetra-O-methyl-~-rnannose, characterized as the phenylhy-dsazide of the corresponcling acid ( 5 ) . The clisaccl~aricle, therefore, was 2-0-D-mannopyranosjil-D-~nar~~~ose; as it has not been crystallized, its possible iclentity wit11 the crystalline l,%nlannobiose synthesized by Gakhol;iclze and Icutidze (6) is not determinecl. Socliu~ll borohj~dricle reduction oi the compound gave crystalline 2-0-D-n~a~~nopyra~~osyl-D-mannitol, which, in agreement with the formulated structure, consumed 5 moles of leacl tetraacetate per mole (12), producing 1 Inole of foi-malclehycle per mole. The configuration of the glycosidic linkage was established bj-controllecl lead tetraacetate oxic1;ltion of the '~l f a ?~u s c r i p t

No abstract

Partial acid hydrolysis of an a-cellulose prepared fro111 white birch (Betula papyrifera) wood has led to the isolation of a new disaccharide (1). The disaccharide is now shown to be 4-0-P-D-galactopyranosyl-D-galactose.

A comparison of nuclear magnetic resonance spectra for isomeric cyclohexane derivatives (methyl, hydroxyl, halogen) shows that net shielding of carbon-13 nuclei of these compounds increases additively with an increase in repulsive non-bonding interactions, and thus with decreasing enthalpy in the series. By contrast, an inverse shielding pattern is found for the appended protons. Hence, a destabilizing interaction in these compounds alters polarization of the C—H bond, placing greater electron density on carbon, and its impact appears to be delocalized over many C—H bonds of the molecule.