Cyclohexanepentols

The deoxyinositols (quercitols, cyclohexanepentols) are useful model compounds which display many of the physical and chemical properties of true deoxy sugars. Although (-b)-proto-quercitol, the best known isomer, was isolated from nature 118 years ago, no synthesis has been reported up until now. The synthesis here described is actually that of the (-)-enantiomer, starting with (-)-inositol however, identical procedures applied to the readily available ( + ) or dl-inositol would give (- -) or DL-proto-quercitol, respectively. The natural occurence of, )-proto-quercitol has... 

The cyclohexanediols, -triols, and -tetrols each have three structures (e.g,. 1,2 1,3 and 1,4 for the diols), but the cyclohexanepentols and -hexols and cyclohexanol itself each have only one structure. For these twelve structures a total of fifty diastereomeric forms (28 meso, 22 racemic) is possible. Cyclohexanol and the -diols have long been known,... 

The Synthesis of (— -proto-Quercitol, Although proto-quercitol (dextro) was discovered in 1849 ( 5), its cyclohexanepentol structure was not established until 1885 (13), and its configuration not until 1932. (38). The synthesis of this well-known cyclitol has been a difficult problem, since it appears that nearly every synthetic reaction commonly employed for other cyclitols would lead stereospecifically to the wrong product. 

In an attempt to elucidate the reaction sequence by which the cyclohexanepentols are oxidized, we recorded simultaneously the time curves of periodate reduction and of malonaldehyde production during the oxidations. By this procedure, it is, in fact, possible to propose a reaction sequence for (1 d)-1, 2, 5/3, 4-cyclohexanepentol. 

Figure 3. Oxidation of (1 i.)-l,2,4/3,5-cyclohexanepentol (curve A minutes Curve C hours) and of (+)-quercitol (curve B minutes curve D hours) with sodium metaperiodate (c.f. Table I).

In the cases of the slowly reacting cyclohexanepentols, more complicated results are obtained. This is probably because of the fact that, as has been pointed out by Angyal and McHugh (2), the rate of oxidation of the product of ring fission is likely to be more rapid than the rate of fission itself. 

Figure 4. Periodate uptake (10f) and malonaldehyde formation (MA) during the oxidation of (1 d)-1,2,5/3,4-cyclohexanepentol with sodium metaperiodate...

No hypotheses can be advanced for the sequences involved in the oxidation of cyclohexanepentols which react even more slowly with periodate than does (+)-quercitol. For instance, when the all-trans l 3, 5/2, 4-cyclohexanepentol (33) is oxidized (Figure 6), production of malonaldehyde starts very early and the time curve of periodate reduction indicates a very complex reaction. Nor is it possible to analyze satisfactorily the curves obtained with (1 l)-1, 2, 4/3, 5-cyclohexane-pentol (34) or with dl-1, 2, 3, 4/5-cyclohexanepentol (35) [this is the configuration predicted for the (1 D)-entantiomorph (41)]. 

It is, in fact, interesting to note that the latter cyclohexanepentol, which has four adjacent cis-hydroxyl groups, reacts slowly with periodate. Perhaps further light will be thrown on this problem when the results of periodate oxidations of dl-1, 2, 3, 5/4-cyclohexanepentol (36), 1, 2, 4, 5/3-cyclohexanepentol (37), and (1 d)-1, 2, 3/4, 5-cyclohexanepentol (38) will be available. 

We are greatly indebted to S. J. Angyal, J. E. Courtois, G. E. McCasland, M. Nakajima, and T. Postemak for gifts of the cyclohexanepentols mentioned, and to A. M. Staub and G. Bagdian who provided us with the polysaccharide material from Salmonella typhimurium. 

Quercitol is a deoxyinositol (1,3,4/2,5-cyclohexanepentol) which appears in certain Dicotyledons including all the Quercus genus (Plouvier 1963). This compound has been found in wines aged in contact with oak wood (barrels or chips) but not in wines aged in bottles (Carlavilla et al. 2006). 

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