13 Gardneria属塩基Gardneramineの構造

概要

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Some time ago four kinds of new alkaloids were isolated from Gardneria nutans Sieb. et Zucc. (Loganiaceae) by us. The structures of three of them, i.e. gardnerine, gardnutine and hydroxygardnutine, were fully established and reported. The present paper deals with the structure elucidation of the last base gardneramine (I), C_<23>H_<28>N_2O_5, mp. 134-135, [α]_D=-287.7 (c=1.06, MeOH), to which the structural formula (I) has been deduced on the basis of the chemical and spectroscopic evidences. The iminoether ring of I can be cleaved by various reagents including HCOOH, AcOH, dil. HCl and CH_3I to give an oxindole derivative. (Chart 1). The revers reaction occurs when the oxindole with an adequate leaving group at C-22 (e.g. V or X) is treated with ethanolic KOH. Demethylgardneramine (XIII) derived from I was proved to be identical with Alkaloid G which had been isolated from G. multiflora Makino in our laboratory. Some efforts are under progress to determine the positions of the methoxyl groups on the benzene ring. Gardneramine is the first natural base with a masked oxindole system in its molecule.
天然有機化合物討論会の論文
1970-10-01