Pentitols configuration

Lespieau, R., Synthesis of Hexitols and Pentitols from Unsaturated Poly-hydric Alcohols, II, 107-118 Levi, Irving, and Purves, Clifford B., The Structure and Configuration of Sucrose (oipta-D-Glucopyranosyl beta-D-Fructofuranoside), IV, 1-35 Liggett, R. W., and Deitz, Victor R., Color and Turbidity of Sugar Products, IX, 247-284... 

Digressing from reductive desulfurization into stereochemistry, we may use this experimental proof of the equivalent symmetry of D-mannitol as a basis for an independent proof of the configurations of D-mannitol and D-arabitol. The reduction of D-arabinose yields the optically active pentitol, D-arabitol application of the Sowden-Fischer synthesis to D-arabinose yields D-mannose86 which upon reduction gives D-mannitol. 

Polyols. Linear polyols containing two carbon to seven carbon atoms all evoked neural responses. Two important results were observed (Figure 8)s (1) The effectiveness (CR q.) of the polyols increased as the chain length increased up to five carbon atoms (2) In contrast to monosaccharides, the configurations of linear polyol may not play a role in the taste response. This is indicated by the identical responses to the four pentitols D-arabinitol, L-arabinitol, D-ribitol, or D-xylitol. 

An interesting point arose in connection with the periodate oxidations of XLVI and XLVII. On examination of the rotations of the crude aldehydes, XLVIII and XLIX, as well as the rotations of the crude acids, L and LI, obtained on subsequent oxidation, it was concluded that the periodate oxidations of XLVI and XLVII had been attended by slight racemization, and that the extent of racemization was determined by the configuration of the 1-C-phenyl-n-pentitol undergoing oxidation. This is the first report of racemization attending periodate oxidation in the carbohydrate series. 

Xylitol 3 is a non-chiral, all-t/zreo-configured pentitol which allows grouping of all its hydroxyl functions on the same side of the C5 chain with a zigzag conformation. In the dinuclear cobalt(III) complex 25 (O Fig. 5) two entirely deprotonated zigzag conformers provide a proper Oio set of an edge-shared C02O10 dioctahedron, whereas in the similar diferrate(III) 16 (O Fig. 3) with the smaller aW-threo configured L-threitol, two hydroxyls are required to complete the dioctahedron [36]. 

Ribitol 5 is a completely eryf/tro-configured pentitol. No crystal structure analyses of a ribitol complex have been reported so far. However, solution studies have been performed with pal-ladium(II) and with molybdenum(VI) and tungsten(VI). 

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