L-Mannose

D,L-Mannitol has been obtained by sodium amalgam reduction of D,L-mannose. The identical hexitol is formed from the formaldehyde polymer, acrose, by conversion through its osazone and osone to D,L-fmctose (a-acrose) followed by reduction (83). 

Chain extension of the aldopentose ( —)-arabinose by way of the derived cyanohydrin gave a mixture of (-l-)-glucose and (-l-)-mannose. 

Nucleophilic Displacement Reactions in Carbohydrates. Part XI. Reaction of Methyl 6-Deoxy-2,3-O-isopropylidene-4-O-methyl-sulphonyl-a-L-talopyranoside with Sodium Azide A Synthesis of L-Perosamine (4-Amino-4,6-dideoxy-L-mannose) Derivatives, J. S. Brimacombe, O. A. Ching, and M. Stacey, J. Chem. Soc. C, (1969) 1270-1274. 

Dideoxy-3-[3-hydroxy-2-(hydroxymethyl)propyl]-4-C-methyl-L-mannose (not the alternative /Ztrco-hexose)... 

Six of the 18 aldohexoses, namely, D-glucose, d- and L-mannose, D-galac-tose, D-allose, and L-altrose have been found in bacterial polysaccharides. 

D-Mannose is common, but L-mannose has only been found in a small group of extracellular polysaccharides of related structures, one of which is elaborated by Alcaligenes ATCC 31555. In these polysaccharides, it is a-linked and partially replaces an a-L-rhamnopyranosyl residue in the pentasaccharide repeating-unit. It seems possible that these sugar residues are scrambled, but the other possibility, that there are two populations of polysaccharides, has not yet been excluded. 

Deoxy-L-mannose (L-rhamnose) is common, but D-rhamnose has only been found in some 0-antigens, as in that of Pseudomonas cepacia IMV 3181, which is a homopolysaccharide containing both a- and y -pyranosyl residues. 

Wellan gum is produced by aerobic fermentation. The backbone of wellan gum is identical to gellan gum, but it has a side chain consisting of L-mannose or L-rhamnose. It is used in fluid loss additives and is extremely compatible with calcium ions in alkaline solutions. 

It was observed in those cases in which the oxidation was arrested too soon that an appreciable amount of silver chloride was deposited when the solution was concentrated. Furthermore, the mother liquor, when treated with phenyl-hydrazine in acetic acid, deposited some yellow crystalline D,L-mannose phenylhydrazone, m. p. 195-200° (Maquenne block). It is apparent that too vigorous oxidation results in the formation of hexoses. 

Bacillus krzemieniewski(f). This soil bacillus forms thick, gelatinous capsules on carbohydrate media and yields a polysaccharide which on hydrolysis is stated to produce L-mannose.660 This claim is based upon the melting point of the isolated mannose phenylhydrazone and upon the rotation of the hydrolyzed reaction mixture. It requires further confirmation. 

C-Nucleoside analogue 464 of this ring system was prepared (86SC35) from 2,5-anhydro-3,4,6-tri-0-benzoyl-L-mannose dimethyl acetal 462 and 6-(2-aminophenyl)-3-methylthiotriazin-5(2//)-one 463 in the presence of acetic and hydrochloric acids. 

L-Gluconic acid 1 L-mannose D-mannose 1 D-gluconic acid 1... 

Fig. 1.—Fischer s Total Synthesis of D-Glucose, D-Mannose, and D-Fructose and of L-Glucose, L-Mannose, and L-Fructose.

Deoxy-3-0-methyl-L-mannose (3-O-methyl-L-rhamnose) HO HO H H HsC—C—C C—C—CHO H H MeO HO black-spruce hemicellulose Strophanthus sp. 

L-Fructose from L-fructose, L-mannose, L-psicose CaY Water [224]... 

L-Mannitol has been prepared by the reduction of L-mannosaccharo-dilactone or L-mannose. By far the most convenient procedure is that used by Baer and Fischer for their preparation of L-glyceraldehyde by the oxidative cleavage of l,2 5,6-diisopropylidene-L-mannitol with lead tetraacetate. L-Arabinose was converted to L-mannonolactone by the cyanohydrin synthesis and this was hydrogenated over platinum oxide to the desired L-mannitol. High hydrogen pressures, rather than low as usually employed with this catalyst, were used. 

The enantiomorphs of a given sugar were found to exhibit no appreciable difference in Ka for example, the values for D- and L-mannose were 0.626 and 0.627, respectively. It appears, therefore, that stereospecific adsorption to the gel, which could possibly result from the presence of the dissymmetric residues of D-glucopyranose in the dextran matrix, is not a significant factor. 

The crystal structure of a-D and a-L-mannose has been solved,22 but full details are not yet available. With calcium chloride, D-raan-nose forms a crystalline compound (C6H,206 CaCl2 4HzO) which appears to contain the furanose ring.23 The crystal structure is of interest because of the furanose ring and the nature of the presumed complex. In the complex are three heavy atoms (one calcium and two chloride ions) which could help in solving the structure. 

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