Pentitols

All of the pentitols predicted by theory are known. As in the case of the tetritols, only the D-configurations of the optically active polyols will be indicated. 

D-Arabitol (III), m.p. 102°, [a] +7.82° (borax) pentaacetate, m.p. 76° has been found in many lichens 13) both in the free form and as umbilicin, 

CH2OH (III) D-Arabitol (o-Lyxitol) CH2OH (IV) Xylitol (meso) 1 CH2OH (V) Ribitol (Adonitol) (meso) 

Synthetically, D-arabitol has been obtained by the reduction of either D-arabinose (15) or D-ljrxose (16) by means of sodium amalgam. 

The reported physical constants of L-arabitol agree with those of the D-form except that the rotation in borax solution is somewhat smaller (Wd 5.4° (17). It does not occur naturally and has been prepared by the reduction of L-arabinose (18) and by employing the Cannizzaro reaction with L-arabinose in the presence of nickel (19). 

The following formulas show the structures of the four pentahydric alcohols or pentitols  

The sugar alcohols with five carbon atoms have never been studied physiologically. These compounds have not been readily available in quantities sufficient to warrant metabolic study. This remains, therefore, an unexplored field. 

As these compounds approximate more closely n-glucose than the other sugar alcohols, those which are readily available have been the subjects of intensive metabolic study.  

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Fig. 1. Stmctures of the tetritols (a) erythritol, (b) D-threitol, and (c) L-threitol and the pentitols (d) ribitol, (e) D-arabinitol, (f) L-arabinitol, and (g) xyhtol.

Polarimetric analysis of sorbitol and mannitol in the presence of each other and of sugars is possible because of their enhanced optical rotation when molybdate complexes are formed and the higher rotation of the mannitol molybdate complex under conditions of low acidity (194). The concentration of a pure solution of sorbitol may be determined by means of the refractometer (195). Mass spectra of trimethylsilyl ethers of sugar alcohols provide unambiguous identification of tetritols, pentitols, and hexitols and permit determination of molecular weight (196). 

Generally speaking, the phosphorylated deoxysugars undergo the usual reactions of carbohydrates without complication. For instance, both 2-deoxy D-ribose 5-phosphate (52, 59) and 2-deoxy D-xylose 5-phosphate (2) can be reduced to the corresponding 2-deoxy d-erythro- (48) and 2-deoxy D-threo-pentitol 5-phosphates (49). 2-deoxy ribose 5-phosphate has also been oxidized (52) to the corresponding phosphorylated acid (50). 

Deoxy-1 - O-methyl-D- fhreo-pent-1 -ynitol or 1,1,2,2-tetradehydro-2-deoxy-1-0-methyl-D-tfjreo-pentitol... 

The Enzymes II (E-IIs) of the phosphoenolpyruvate (P-enolpyruvate)-dependent phosphotransferase system (PTS) are carbohydrate transporters found only in prokaryotes. They not only transport hexoses and hexitols, but also pentitols and disaccharides. The PTS substrates are listed in Table I. The abbreviations used (as superscripts) throughout the text for these substrates are as follows Bgl, jS-gluco-side Cel, cellobiose Fru, fructose Glc, glucose Gut, glucitol Lac, lactose Man, mannose Mtl, mannitol Nag, iV-acetylglucosamine Scr, sucrose Sor, sorbose Xtl, xylitol. 

C20H22O4 2(S)-4-0-Acetyl-3,5-0-benzylidene-l,2-dideoxy-2-C-phenyl- D-en/t/iro-pentitol ABYPEP 38 472... 

CnHJ7FN206S 1 -S-Ethyl-1 -(5-fluorouracil-1 -yl)-1 -thio-D-giuco-pentitol DETFUA10 38 493... 

SYNTHESIS OF HEXITOLS AND PENTITOLS FROM UNSATURATED POLYHYDRIC ALCOHOLS... 

The syntheses of certain hexitols and pentitols that are reviewed in the present article were begun about 1928. Their origin is related to an investigation made by G. Griner thirty-six years previously, the essential results of which will now be described. 

III. Synthesis of Pentitols from Unsaturated Intermediates 1. Methods of Preparation... 

Very little work on the synthesis of pentitols had been carried out before 1928. Those pentitols which had been synthesized were made by the reduction of pentoses. Several pentitol intermediates had been synthesized" and it seemed desirable to attempt to complete the synthesis of pentitols from the unsaturated intermediates, using the methods which had been successfully employed in the synthesis of hexitols. 

Triacetoxypentanediol-l,8. The preceding triacetoxypentene was converted to a mixture of two isomeric pentitol triacetates, CHaOAc—... 

Hydrogenation of the pentenynol with Bourguel s catalyst5 gives the corresponding divinylcarbinol, CH2=CH—CHOH—CH=CH2, b. p. 114.5-116°, dig 0.8648, mdw 1.4452. Treatment of this divinylcarbinol with the theoretical quantity of silver chlorate and a little osmic acid yielded a sirup which has not crystallized. From the acetylation of this sirup there was obtained a small quantity of D,L-arabitol pentaacetate and a viscous liquid which has not been studied further but certainly contains one or both of the other pentitol pentaacetates. 

A MS to promote thermal cyclodehydration has been reported for such pentitols as... 

M. Kurszewska, E. Skorupowa, J. Madaj, and A. Wisniewski, Solvent-free thermal dehydration of pentitols on zeolites, J. Carbohydr. Chem., 23 (2004) 169-177. 

Barker, S. A., and Bourne, E. J., Acetals and Ketals of the Tetritols, Pentitols and Hexitols, VII, 137-207 Barrett, Elliott P., Trends in the Development of Granular Adsorbents for Sugar Refining, VI, 205-230 Barry, C. P., and Honeyman, John, Fructose and its Derivatives, VII, 53-98... 

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... 

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