Regiocontrolled incorporation and annulation of glucose into spirothiazoleand spirothiazoloxazole derivatives

Cyclic ketones 1a-f reacted with mercaptoacetic acid in benzene and/or tolu ene in the presence of p-toluenesulfonic acid afforded the corresponding sp iro-1,3-oxathialanone derivatives (2a-f). Compounds 2a-f reacted with gluco samine hydrochloride in a mixture of pyridine and ethanol to yield 3-(2'-gl ucosyl)-2-spiro[1'-cycloalkyl]thiazolidin-4-one derivatives 4a-f. Reaction of 4a-f with fused sodium acetate in a mixture of acetic anhydride and acet ic acid gave annulated spirothiazoloxazologlucose derivatives 6a-f. All the synthesized spiro derivatives were identified by conventional methods (IR, H-1 NMR spectroscopy and elemental analyses).