Hofmann degradation of ushinsunine (I) gives an optically inactive methine base of m.p. 108-109°, whose composition agrees with the formula C₁₉H₁₇O₂N. The ultraviolet and infrared spectra of this substance indicated new formation of a double bond conjugated to the benzene ring, disappearance of a hydroxyl group, and new formation of a terminal vinyl group. From these evidences, formula (III) was assumed for this methine base.
Treatment of ushinsunine (I) with phosphoryl chloride in pyridine solution produces optically inactive anhydroushinsunine (VI), m.p. 88-89°, C₁₈H₁₅O₂N. This fact suggests the presence of alcoholic hydroxyl in the 6a- or 7-position of the aporphine ring. It had been found in the previous work that ushinsunine is easily acetylated and quantitatively forms a basic monoacetate. This fact endorses the presence of a secondary hydroxyl in 7-position in ushinsunine molecule.
The Clemmensen reduction of (I) afforded an optically inactive dehydroxyushinsunine, m.p. 87-88°, C₁₈H₁₇O₂N, which was identified with dl-roemerine (VIII). It follows, therefore, that the methylenedioxy group in ushinsunine is in the 1-2 position of the aporphine ring.
Oxidation of ushinsunine (I) with chromium trioxide-pyridine afforded oxoushinsunine, C₁₇H₉O₃N, as pale yellow needles, m.p. 280-282°(decomp.), which was found to be entirely identical with liriodenine (XIII), synthesized by Taylor independently. It had already been reported that this oxoushinsunine is contained in the heartwood of this plant, together with ushinsunine. The same oxoushinsunine is obtained on oxidation of ushinsunine with manganese oxide in chloroform but Oppenauer oxidation of (I) results in the recovery of the starting base. Oxidation of l-roemerine (VIII) with chromium trioxide-pyridine also affords oxoushinsunine.
All these facts may be explained by the formation of (XV) to (XVI) to (XIII), during the oxidation of ushinsunine (XII) or roemerine (VIII) to oxoushinsunine (liriodenine) (XIII), and ushinsunine may be considered as the initial oxidation product of roemerine.