1957 年 77 巻 9 号 p. 997-1003
Detailed investigations have been made on insularine, the main alkaloid of Cyclea insularis (MAKINO) DIELS and an assumed structural formula (I) was forwarded. However, steric configuration of the two asymmetric centers of insularine has been left unsolved. This question was solved in the present series of experiments by cleavage reaction of insularine with sodium in liquid ammonia.
Cleavage of insularine afforded two kinds of crystalline phenolic bases, A and B, and one kind of noncrystalline phenolic base, C. Of these, B base agreed with l-N-methylcoclaurine (IV). A is a new base, not found in any literature to date, corresponding to the composition of C20H25O3N, which was designated l-homoarmepavine and determined as l-1-(3-methyl-4-hydroxybenzyl)-2-methyl-6, 7-dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline (III).
O-Alkylation of the C base followed by second cleavage with sodium in liquid ammonia afforded l-homoarmepavine (III) and l-O, O-dialkyl-N-methylcoclaurine (VI), from which the C base was found to be a bis-type structure like (Va) formed by the partial cleavage of the depsidan ring in insularine.
These experimental results have proved that the steric configuration of the two asymmetric centers in insularine (I) is l-form in both and that the structure (I) proposed by Tomita and Uyeo is correct.