As a model experiment for the synthesis of A, B rings of tetracyclines, the synthesis of 9-hydroxydecalin-l, 3-dione(Ⅷ) is reported.Ethyl 2-ethynyl-2-hydroxycyclohexaneacetate(Ⅲ), b.p.105-7°/0.1mm, and its corresponding acid(Ⅳ), m.p.100-1°, were obtained by the ethynylation of ethyl cyclohexanone-2-acetate(Ⅱ).Hydration of Ⅲ, followed by hydrolysis, gave 2-acetyl-2-hydroxycyclohexaneacetic acid(Ⅴ), m.p.115-7°, which on esterification with diazomethane yielded its methyl ester(Ⅵ), m.p.37-8°.The latter was cyclized by sodium methoxide to form 9-hydroxydecalin-1, 3-dione(Ⅷ), m.p.182-3°, which showed characteristic concentration-dependent ultraviolet absorption spectra of cyclic 1, 3-diketones.