L-Altrose

Ionophoresis of Carbohydrates. Part VII. 2,5-Di-O-methyl-L-rhamnose Its Ionophoresis and Conversion into 6-Deoxy-2 5-di-0-methyl-L-altrose, A. B. Foster, J. Lehmann, and M. Stacey, /. Chem. Soc., (1961)4649-4653. 

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-Allose and L-altrose are components of the extracellular polysaccharides elaborated by Pseudomonas viscogena and Butyrovibrio fibrisol-vens, respectively. 

Using the C-5 epimeriztion strategy used to convert D-glucose into L-idose, but starting with a D-galactoseptanose derivative (such as 47) delivered the L-altrose isomer 50 (Scheme 10). Treatment of 5-O-benzyl-1,2-O-isopropylidene-a-D-galactoseptanose... 

L-Talitol has been synthesized by the catalytic hydrogenation of L-altrose. It was the last of the ten isomeric hexitols to be synthesized. 

These values indicate that the rate of reaction of D-altrose with D-tartrate is the same as that of L-altrose with L-tartrate and that other rates pair up similarly. Similar data were obtained for some other pairs of enantiomers. Unfortunately no kinetic data are available on these systems. 

L-talaric acid, which could also arise from L-talose or L-altrose. It was possible to eliminate the latter alternative, because talose was known to be the epimer of galactose, l-Talose thus has formula (22), and its enantio-morph is epimeric with D-galactose. Therefore, D-galactose has formula (14). 

Such a situation is rather common for D-galactose and the structurally related monosaccharides L-arabinose218 and D-fucose thus far, the latter monosaccharide has been identified only as the furanose form in the O-specific polysaccharide of Eubacterium saburreum.219 6-Deoxy-L-altrose is present as the pyranose in the lipopolysaccharide of Yersinia enteroco-litica,20 but as the furanose in a similar polymer220 of Y. pseudotuberculosis type VB. Paratose, which is usually present in polysaccharides as the a-pyranose, was identified as the /3-furanose in the O-specific polysaccharide221,222 of Y. pseudotuberculosis serotype IB. 

The benzyl ether 48, generated from (+)-20, afforded 49 which furnished L-altrose via route A and L-talose via route B through the hemiacetal 50 (Scheme 14).16... 

Crystalline L-altrose was described in 1934 by Austin and Humoller. After improving the methods for the preparation of L-ribose," they applied the cyanohydrin synthesis to 30 g. of that sugar and obtained 17 g. of crystalline calcium L-altronate and 14.5 g. of crystalline L-allono-7-lactone. Reduction of the latter with sodium amalgam yielded crystalline L-allose. The calcium L-altronate, by appropriate reactions, was converted to L-altrose, and the last of the sixteen theoretically possible aldohexoses had been prepared. Data on L-altrose and its derivatives are included in Table I. 

Crystalline L-altrose, which had been obtained through the reduction of L-altronolactone with sodium amalgam in cold, weakly acid solution,... 

Although no mutarotation was observed with the first small sample of D-altrose, its [a]D value of +32.6° in water was in agreement with the equilibrium rotation —32.3° recorded by Austin and Humoller for L-altrose. When a larger amount of the sugar became available, D-altrose was found to exhibit a complex mutarotation. From calculations of the velocity coefficients it would appear that the mutarotation consists of a very rapid interconversion of furanose and pyranose modifications, followed by a slower interconversion of o and /3 pyranose modifications. 

Haworth, Raistrick and Stacey discovered that the action of Peni-cillium varians on glucose produces a polysaccharide which they named varianose. By the usual methylation procedures, varianose was found to be composed of about 70% D-galactose, 14% D-glucose, and 14% of a third hexose which they believed to be either D-idose or L-altrose however, from the evidence presented by those authors, it is not clear to the reviewer how D-idose would be possible. The third component was isolated as a liquid methyl trimethylhexoside of —15.6° in 2%... 

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