Alditols dehydration

Efforts were made by Garcia Gonzalez and his coworkers to elucidate the mechanism of this reaction. In one of the working hypotheses, it was considered that the aldehydo form of the sugar and the 1,3-dicarbonyl compound undergo an aldol reaction to yield a 2-C-(alditol-l-yl)-l,3-dicar-bonyl compound, which is then dehydrated to form the furan. This hypothesis was supported by the isolation of the aldol-addition product of... 

Hough and Richardson58 explored the reaction of unacetylated hexose dithioacetals with peroxypropanoic acid the sulfone 15 initially formed is only marginally stable, and undergoes dehydration to mixtures of the unsaturated disulfone (18) and the 2,6-anhydro-l-deoxy-l,l-bis(ethylsulfo-nyl)alditol (19). All three products are degraded by aqueous ammonia to the next lower sugar (16) and bis(ethylsulfonyl)methane (17). This degradation is much slower for 18 than for 15, and it was concluded that hydration of 18 to 15 precedes disproportionation (Scheme 8). 

The 1,2,4-triazine homo C-nucleosides prepared so far are the 1,2,4-triazin-6-yl type. Acid-catalyzed dehydrative cyclization products of the polyhydroxyalkyl chains of 6-(alditol-l-yl)l,2,4-triazines (1065) (Section XXX,D) were first assigned the corresponding 6-()3-glycofuranosyl)-l,2,4-... 

K. Bock, C. Pedersen, and H. Thogersen, Acid catalyzed dehydration of alditols. Part I. o-glucitol and D-mannitol, Acta Chem. Scand., B35 (1981) 441 49. 

Anhydro-alditols. - The solvent-free thermal dehydration of tetritols on zeolites has been studied. At temperatures in excess of 250 C a mixture of products is obtained arising predominantly from intramolecular dehydra-... 

I. 2 Anhydro-alditols. - A review (in Polish) on the dehydration-cyclization of pentitols and hexitols of plant or mammalian origin in aqueous acid or of O-tosyl derivatives under basic conditions has appeared. ... 

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