Pentitols acetals

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... 

The acetals and ketals which will be considered are those formed from the tetritols, pentitols, and hexitols, on the one hand, and the simpler carbonyl compounds (e.g. acetone and benzaldehyde), on the other. 

The Oxidation of Acetals and Ketals of the Pentitols with Glycol-splitting Reagents... 

With the aid of these rules, we have predicted the structures of the acetals which would be expected to result from the benzylidenation, ethylidenation and methylenation of all the tetritols, pentitols and hexi-tols. As will be seen from Table IV, the predicted structures agree very well with the accepted structures of the compounds. The rules explain, too, the syntheses of 3,5-benzylidene- and 3,5-methylene-gluco-[Pg.180]

A similar approach to enantiomericaUy pure norbornene derivatives was developed by Nouguier et al. who employed l,3 2,4-di-0-methylene acetals of pentitols as chiral templates [62]. Hence, the 5-(5-acryloyl-D-arabinatol derivative 82 underwent highly stereoselective Lewis acid catalyzed cycloaddition with cyclopentadiene, giving 83 (Scheme 10.28). The stereochemical outcome of the reaction was explained in terms of the chelate complex 84, in which the chair-like dioxane ring and the acrylic moiety are fixed in two parallel planes, forcing the diene to approach the cisoid acrylate from the ii-face. The synthesis and utihty of various methylene protected glycosides have also been reported by this group [63-66]. 

Attempts to prepare esterified glycals by the reduction of glycofuranosly halides with zinc in acetic acid failed, because of the reactivity of this class of compound (see p. 92). When, however, 3,5-di-0-benzoyl-2-0-(p-nitrophenylsulfonyl)-/3-D-ribofuranosyl bromide (8) in acetone is treated at 5° with sodium iodide, a facile elimination takes place and 3,5-di-O-benzoyl-1,2-dideoxy-D-er2/i/iro-pent-l-enofuranose (9) is obtained crystalline, in 72% yield. The product was characterized by identifying its hydrogenation product as the known l,4-anhydro-3,5-di-0-benzoyl-2-deoxy-D-er2/nuclear magnetic resonance spectrum, which showed clearly that the glycal structure was present. 

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