Studies on the Constituents of Digitalis purpurea L. IX. The Structures of Gitostin and Neogitostin.

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The structure of neogitostin, newly isolated from digitalis seeds by the writer and described in the preceding paper, was examined by enzymatic decomposition using the same enzyme isolated from a snail (Euhadra quaesita DESHAYES) as described in Part IV of this series. It was found that hydrolysis of amorphous neogitostin afforded strospeside and digitalinum verum. However, hydrolysis of monoacetates of gitostin and neogitostin, under the same conditions as those used in the partial decomposition of gitostin to form digitalinum verum but by shortening the duration of hydrolysis, glucose alone was found to be hydrolyzed from these monoacetates, affording digitalinum verum monoacetate. From these results, it was found that gitostin and neogitostin are isomeric triglycosides whose terminal glucose is linked to the terminal glucose in digitalinum verum. By respective acetolysis of gitostin nonaacetate and neogitostin nonaacetate, it was established that gitostin is gitoxigenin-β-cellobiosido-β-D-digitaloside and neogitostin is gitoxigenin-β-gentiobiosido-β-D-digitaloside.