Dulcitol tetraacetate

Oxidation of l,2,5,6-tetraacetoxyhexene-3 led to the formation of dulcitol tetraacetate. In a typical experiment 22 g. of the tetraacetate was oxidized with 4.4 g. of silver chlorate and 0.1 g. of osmic acid and yielded a sirujj which did not crystallize. The sirup was acetylated again and yielded the corresponding hexitol hexaacetate. The crystals which deposited first were collected and recrystallized from methanol, in which they are difficultly soluble in the cold. The product melted at 166-166.5° and analyzed correctly for a hexitol hexaacetate. Now there was found in the collections of the Ecole Normale Sup rieure an old bottle containing dulcitol hexaacetate, m. p. 167-168°. A mixture of the new and the old hexaacetates was found to melt at 166.5-167.5° the identity of the two compounds was thus beyond doubt. 

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. 

Anhydro-D-dulcitol (XXXV) has been prepared by a method which demonstrates its structure. Hockett and coworkers11 prepared it from methyl 3,6-anhydro-a-D-galactopyranoside but both the anhydride itself and its tetraacetate were liquid. Carr63 obtained another anhydro derivative of dulcitol by heating it with phosphoric acid. This also was a liquid but gave rise to a crystalline dibenzoate and a dicarbanilate and was a dianhydro derivative, but no constitutional studies have yet been carried out on this substance. 

D-Mannitol, sorbitol and dulcitol are oxidized at the same rate by lead tetraacetate. 

Reeves88 that a benzylidene-l,4-anhydro-D-mannitol rearranges in this solvent. The use of lead tetraacetate in glacial acetic acid at a high temperature led Pizzarello and Freudenberg61 to assign an incorrect structure to a-diisopropylidene-dulcitol, as was shown by Hann, Maclay and Hudson.86... 

In 1942, Hann, Haskins and Hudson48 reported that the di-(o-nitro-benzylidene)-dulcitol described by Tanasescu and Macovski was not oxidized by lead tetraacetate and therefore could not possess the structure (1,2 5,6) arbitrarily assigned to it by the earlier workers. In view of the fact that the diacetal gave the known l,3,4,6-tetraacetyl-2,5-diben-zoyl-dulcitol when it was benzoylated in pyridine and then acetylated under acidic conditions, they regarded it as l,3 4,6-di-(o-nitrobenzyli-dene)-dulcitol, but of course this conclusion is not unequivocal. 

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