Pentitols synthesis

Pentitol synthesis An asymmetric synthesis of L-arabinitol involves condensation of the (E)-a,fJ-unsaturated ester (2) with the anion of methyl (R)-p-tolyl sulfoxide (1). The resulting p-keto sulfoxide (3) is reduced stereoselectively by ZnCl2/DIBAH (13, 115-116) to 4. Osmylation of 4 with (CH,)3NO and a catalytic amount of 0s04 (13, 224-225) yields essentially a single triol (5). Finally, a Pum-merer rearrangement of the sulfoxide followed by reduction of an intermediate... 

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

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. 

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... 

This approach provides a new method for carbohydrate synthesis. In the synthesis of tetritols, pentitols, and hexitols, for example, titanium-catalyzed asymmetric epoxidation and the subsequent ring opening of the thus formed 2,3-epoxy alcohols can play an essential role. 

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. 

R. Lespieau, Synthesis of Hexitols and Pentitols from Unsaturated Polyhydric... 

In the context of the synthesis of carbohydrate-based amphiphilic (alkylsulfanyl) polyols, Beaupere and co-workers explored the access to 5- and 6-alkylsulfanyl derivatives of pentono- and hexonolactones and their corresponding 1-(alkylsulfanyl) pentitol or l-(alkylsulfanyl)hexitol [38, 39]. Bromolactones 27 and 30 were treated... 

In an extension of diis process, the intramolecular hydrosilylation of a-hydroxy enol ediers has been presented as a new, syn selective route to 1,2,3-tiiols (Scheme 11). Witii such sensitive substrates, a neutral hydrosilylation catalyst, Pt [(CH2>—C MeaSiljO) . must be used. The utility of this method has been demonstrated in a synthesis of the pentitols, o-ar inol and xylitol (as tiieir pentaacetates), in optically pure form. 

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]. 

Gras, J L, Poncet, A, Nouguier, R, Ligand assisted asymmetric synthesis. II. Diastereoselective Diels-Alder additions with Lewis acid attracting auxiliaries derived from pentitols. Tetrahedron Lett, 33, 3323-3326, 1992. 

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