Mannose pentaacetate

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. 

Anomeric ediyl hemiacetals of the methyl ester of aldehydo-D-galacturonic acid tetraacetate were prepared by Dimler and Link. In chloroform, these isomers mutarotated to an intermediate value over a period of several hours, and the mutarotation was complex. Solvent-free oldehydo-D-galactose pentaacetate was obtained in crystalline form, and did not show mutarotation in 1,1,2,2-tetrachloro-ethane. " In the presence of water, the corresponding crystalline aldehydrols of aZde/tydo-D-galactose pentaacetate and aldehydo-T>-mannose pentaacetate were obtained. 

Aldehydo-d-Mannose Pentaacetate Ethyl Hemiacetal, M. L. Wolfrom, M. Konigs-berg, and D. I. Weisblat.J- Amer. Chem. Soc., 61, 574-576 (1939). 

D-Mannose diethyl thioacetal pentaacetate to 1-desoxy-D-mannitol — — — — 36 22... 

The compound of Micheel and Micheel was obtained in small amount after treatment of 2,3,4,6-tetra-O-acetyl-a-D-mannosyl bromide with tri-methylamine the bulk of the material remained unchanged. The product apparently resulted from hydrolysis by moisture from the air. The composition was established by analyses, but the identification was reported with a question mark. A 2,3,4,6-tetra-O-acetyl-D-mannose with different physical constants (m.p. 93°, [c ]d +26.3°) was obtained by Levene and Tipson63b by the deliberate addition of water and silver carbonate to tetra-O-acetyl-D-mannopyranosyl bromide its structure was confirmed by conversion to the known pentaacetates. If Micheel and Micheel were correct in their identification, the two acetates could be anomers. The acetylation and deacetylation reactions performed by Maurer and Bohme are additional evidence in favor of this relationship. 

Gomez, A M, Moreno, E, Valverde, S, Lopez, J C, Stereodivergent synthesis of carbasugars from d-mannose. Syntheses of 5a-carba-alpha-D-allose, beta-L-talose, and alpha-L-gulose pentaacetates, Synlett, 891-894, 2002. 

On the other hand, the amorphous D-mannose phenylhydrazone acetate described by Hofmann,and more recently by Stepanenko and coworker underwent reaction but failed to produce the readily crystalline D-mannose diphenylformazan pentaacetate obtained by the acetylation of D-mannose diphenylformazan. The amorphous, acetylated D-mannose phenylhydrazone has a wide melting-point range and appears to be a mixture of partially acetylated phenylhydrazones in which the presence of the aldehydo form can be readily demonstrated by the formazan reaction. 

In a reapplication of the cyanohydrin synthesis to L-rhamnose, the crystalline T-deoxy-L-jfZj/cero-L-gfalacto-heptose was further characterized as the pentaacetates and methyl glycosides. The heptoses derived from D-galactose and n-mannose have been prepared by the nitromethane synthesis, and this can be the method of choice for sugars which are not preferred epimers in cyanohydrin synthesis. 

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