Mannose methyl ethers

Aspinall, G. 0., The Methyl Ethers of Hexuronie Acids, IX, 131-148 Aspinall, G. 0., The Methyl Ethers of D-Mannose, VIII, 217-230... 

The same procedure has revealed that the aldobionic acid obtained from damson gum and cherry gum by acid hydrolysis has the structure V. Methylation gives the methyl ether VI and when this is subjected to hydrolysis with dilute mineral acid there results 3,4,6-trimethyl-D-mannose (VII) and 2,3,4-trimethyl-D-glucuronic acid (VIII). 

An analogous phenomenon has also been observed with D-mannose pentaacetate and D-altrose pentaacetate. The increase in intensity of the Ai peak in the mass spectra of a-(d or l) anomers may be explained as due to the unfavorable steric position of the OAc group at C-l, analogous to that in the methyl ethers. 

The importance of the methyl ethers of D-mannose lies largely in their occurrence in structural studies in the polysaccharide field. Since previous articles in this series14 have discussed the basic principles involved in the preparation and elucidation of the structure of partially methylated aldoses, it is not intended to give unnecessary details in cases where general procedures are already familiar. 

The following Tables (II, III, and IV) record appropriate data and references relating to the methyl ethers of some hexuronic acids and their derivatives. In the case of methyl ethers of aldobiouronic acids (Table V), data have been recorded only for crystalline derivatives. Where uronic acids have been characterized by reduction to the corresponding hexose, reference should be made to the previous articles in this series dealing with the methyl ethers of D-glucose,71 D-galactose,72 and D-mannose.73... 

In this manner 6-methyl-D-glucopyranose (XXIX) and some of its derivatives were synthesized from n-glucose derivatives containing a free hydroxyl group only in the 6-position. The 6-methyl ethers of D-mannose and of methyl a-n-mannoside were obtained similarly. Haworth and coworkers synthesized 2,3,4-trimethyl-n-glucose from 6-trityl-D-glucose and used the ether for the elucidation of structural problems. 

G. O. Aspinall, and G. Zweifel, Selective esterification of equatorial hydroxyl groups in the synthesis of some methyl ethers of D-mannose, J. Chem. Soc. (1957) 2271—2278. 

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