Xylose diethyl dithioacetal, methylation

Tetra-Me 2,3,4,5-Tetra-O-methyl-D-xylose diethyl dithioacetal [52545-19-4]... 

Tri-O -methyl-D-xylose, M-307 Xylose dibenzyl dithioacetal T>-form, X-82 Xylose diethyl dithioacetal xy-form, X-83 Xylose diethyl dithioacetal . -form, X-83... 

Acid-catalyzed acetonation of L-sorbose gave a mixture of di-O-iso-propylidene and mono-O-isopropylidene derivatives, easily separated by the solubility of the former in benzene. Isopropylidenation of 2-acetamido-2-deoxy-D-xylose diethyl dithioacetal gave the 4-j5- -iso-propylidene derivative accompanied by some 3-0- 1-methoxy-1-methyl-ethyl ) -derivative (/i) when copper(Il) sulphate was used as catalyst with either propanone - 2,2-dimethoxypropane or propanone - 2-meth-oxypropene. The 3,4--0-isopropylidene derivative was obtained when sulphuric acid was used as catalyst in propanone - 2,2-dimethoxypropane. The former was considered the kinetic, and the latter the thermodynamic product. 3,4-0-Isopropylidene-L-fucopyranose... 

Further examples of rearrangements involving cyclic sulphonium ions have been reported. Thus 2,3,5-tri-0-methyl-4-0-toluene-/>-sulphonyl-D-ribose diethyl dithioacetal (184) and dibenzyl dithioacetal (185) gave 4- S -ethyl-2,3,5-tri-0-methyl-4-thio-L-lyxose (186) and benzyl 2,3,5-tri-0-methyl-l,4-dithio-a-L-lyxo-furanoside (187) (Scheme 46) when heated either in aqueous pyridine or with sodium iodide in acetone similar rearrangements to the 4-thiofuranosides were observed with 2,3,5-tri-0-methyl-4-0-toluene-p-sulphonyl-D-xylose and -lyxose... 

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