Mannans methyl ethers

Yeast mannan Methyl ether O. P. CHCl. (18-76)10 90-380 — Branched 67... 

Methyl ethers of Man, mono-substituted at the 2, 3, 4 or 6 positions have been reported in the lipopolysaccharides of photosynthetic procaryotes [82, 83]. The reducing end of the mannans from Mycobacterium smegmatis and Streptomyces griseus have a terminal a-O-methyl group on C-l and Man30Me in the polymer chain. The lactic acid ether 4-0-[-(S)-l- carboxyethyl]-D-mannose is a component of extracellular polysaccharides of Mycobacterium spp., and a-amino-3-0-[-... 

In a model study on the methyl ethers of n-mannose, the 2,3,4,6-and 2,3,5,6-ethers, as well as the 2,5,6- and 3,5,6-tri-O-methyl-D-mannoses, were best distinguished as the trimethylsilyl derivatives of the free sugars, and Gray and Ballou used these derivatives in their examination of a mannan from Mycobacterium phlei. 

Bacillus polymyxa mannan. The purified mannan [a]n -f-82 was electro-phoretically homogeneous but appeared to contain some 13 % bound protein or peptide. Methylation with dimethyl sulphate/NaOH and later silver oxide/methyl iodide in dimethylformamide afforded a methyl ether [a]n +92 in chloroform and containing OCH3, 38.2%. Formic acid hydrolysis followed by further treatment with o.i N hydrochloric acid gave a mixture of ethers characterised as 2,3,4,6-tetra-O-methyl-D-mannose (identified by oxidation to the lactone and isolation of a crystalline phenylhydrazide),... 

Preliminary to a second-generation synthesis of the 3-(9-methyl-y-( 1 -4)-mannans, Kishi and co-workers screened a series of mannosyl phosphates for the influence of the 0-2 protecting group and the anomeric stereochemistry of the donor on the outcome of the glycosylation reaction. As may be seen from Scheme 26, the use of benzyl ether protection under these homogeneous solution-phase conditions gave selectivities that were insufficient, whereas the 2-benzoates gave exquisite a-selectivity.34... 

The presence of 2,3,4- and 2,4,6-tri-O-methyl-D-mannoses had been overlooked in earlier work in which the separation of the methyl mannosides had been attempted on Apiezon M. When the methyl glycosides were separated as their trimethylsilyl ethers on Carbowax 6000, resolution of the 2,3,4, 2,4,6, and 3,4,6 isomers was achieved. Bauer and coworkers have continued with the application of this method in their work on yeast mannans. 

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