Cyclic Polyhydroxy Ketones II. xylo-Trihydroxycyclohexenediolic Acid and Keto-Inositols

A new crystalline compound, dl-xylo-trihydroxycyclohexenediolic acid (dl-xylo-pentahydroxy-2-cyelohexen-1-one) (I), has been isolated from the products of oxidation of myo-inositol with nitric acid, and its structure has been established. Compound (I) reduces Tillmans reagent, reacts with iodine in neutral or slightly acidic solution, produces a blue color with ferric chloride solution, and exhibits other properties characteristic of an enediolic acid. On catalytic reduction, it gives both scyllo-inositol and myo-inositol. On oxidation, it yields a new triketo-inositol, xylo-4,5,6-trihydroxycyclohexane-l,2,3-trione (II). Under acidic conditions, catalytic acetylation of I gives two pentaacetates, the infrared spectra of which are similar but not identical. One of these acetates exists in two forms, both of which, on deacetylation, yield the parent acid I. The product formed by deacetylation of the other pentaacetate has not been identified. Benzoylation of I gives a crystalline pentabenzoate. Under basic conditions, acetylation of I proceeds with simultaneous aromatization, resulting in the formation of pentaacetoxybenzene, from which pentahydroxybenzene is obtained by hydrolysis. xylo-4,5,6-Trihydroxycyclohexane-l,2,3-trione (II) gives a crystalline bis(phenylhydrazone). By acetylation under basic conditions, it yields hexaacetoxybenzene. Mechanisms are presented for the aromatization of keto-inositols by enolization and beta elimination-reactions, and certain observations reported in the literature are rationalized. Infrared and ultraviolet absorption spectra are reported for the new compounds.