Anhydrides of hexitols

4-Anhydro-D-mannitol is also obtained by a novel route from 1,6-dibenzoyl-D-mannitol. When this compound is heated with p-tolu-enesulfonic acid in acetylene tetrachloride, it suffers partial dehydration and one of the products is a dibenzoyl derivative of mannitan. On debenzoylation of this substance it yields crystalline 1,4-anhydro-D-mannitol.67 The formation of dibenzoyl-1,4-anhydro-D-mannitol has involved the migration of at least one benzoyl group and Hockett and coworkers6 believe that the initial product is either 2,6- or 3,6-dibenzoyl-1,4-anhydro-D-mannitol. 

The same anhydride of mannitol has been obtained recently by the deamination of 1-amino-l-desoxy-D-mannitol.8 It is interesting to note that this method of formation of anhydro rings is of fairly general application. Thus 1,4-anhydro-D-sorbitol is obtained from 1-amino-l-desoxy-D-sorbitol. Similarly, methyl 2,3-anhydro-4,6-benzylidene-a-D-manno-pyranoside and methyl 2,3-anhydro-4,6-benzylidene-a-D-allopyranoside9 

Crystalline 1,4-anhydro-D-sorbitol is of much more recent origin than 1,4-anhydro-D-mannitol, inasmuch as its preparation was first recorded in 1946.10 It was obtained by the restricted dehydration of D-sorbitol and has been given the trivial name arlitan. Two groups of workers simultaneously effected proof of its constitution. Hockett and coworkers11 treated the anhydride with lead tetraacetate and since its rate of oxidation coincided with that of ethyl D-galactofuranoside and since one molecular proportion of formaldehyde was formed, the authors concluded that the ring must involve Cl and C4 of a hexitol chain. Assuming that no other carbon atoms are involved, sorbitan is either 1,4-anhydro-D-sorbitol or 1,4-anhydro-D-dulcitol (Walden inversion at C4 of the sorbitol molecule). They therefore synthesized 3,6-anhydro-D-dulcitol (enantio-morphous with 1,4-anhydro-L-dulcitol) but found it to be different from arlitan. 

Soltzberg, Goepp and Freudenberg10 proved the constitution of arlitan by a synthetic method. They obtained a liquid tetramethyl derivative of arlitan, characterized it by its boiling point, density and refractive index, and compared it with 2,3,5,6-tetramethyl-l,4-anhydro-D-sorbitol (V) synthesized by the following method. Tetramethyl-D-glucofuranose 

A further proof of the structure of arlitan has been given by Bashford 

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Although the polyhydric alcohols derived from sugars have been the subject of numerous investigations over many years, the inner ethers or anhydrides of these substances have been for the most part neglected, despite the fact that many of them were isolated and some description of their properties recorded before the advent of the twentieth century. In recent years, however, the anhydrides of polyhydric alcohols derived from sugars have received marked attention in several countries. Some indeed have achieved importance in chemical industry. Most interest has been centered on the anhydrides of pentitols and hexitols and this article will be restricted to a discussion of the chemistry of these substances. 

An article on the anhydrides of polyhydric alcohols appeared in Volume 5 of this Series,1 and it is the purpose of the present article to bring the subject up to date. Wiggins article1 was limited to the anhydrides of the pentitols and hexitols the present article will include the anhydrides of tetritols and of alditols higher than the hexitols. However, anhydrides having the three-membered (oxirane) ring will not be considered, as they are discussed elsewhere in this Volume.13 2,5-Anhydrides of aldoses are also treated in this Volume.lb... 

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