Ribopyranose hydrolysis

Trimethyl-D-ribopyranose has been obtained51 by the methylation of methyl ribopyranosides (a/3 mixture) with methyl sulfate and sodium hydroxide, followed by hydrolysis. 

Free 5-thio-D-ribopyranose (227) may be prepared by hydrolysis of the D-ribofuranoside 228 with sulfuric acid on standing for several months, the product crystallized as an anomeric mixture. The thiopyranoid ring form is established by the absence of the thiol band in the infrared spectrum of 227. 

Thio-D-ribopyranose derivatives have been prepared by similar procedures. " " Thiolacetate replacement of the 5-substituent in methyl 2,3-0-isopropyhdene-5-0-p-tolylsulfonyl-/3-D-ribofuranoside (127), followed by saponification and acid hydrolysis in an inert atmosphere, gave a sirup formulated as 5-thio-D-ribopyranose (128) on the basis of its slow reaction with iodine acetylation converted it into a crystalline. 

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