防已科植物アルカロイド研究 (第207報)

TrilobineおよびIsotrilobineの構造 その17 OxyacanthineよりIsotrilobineの合成

抄録

Following the previous work on the synthesis of the antipode of isotrilobine (VI) from the antipode (N-methyl-dihydroepistephanine-B) of O-methylrepandine (II), O-methylanhydrodemethylrepandine (VI) was synthesized from repandine (III), obtained by the treatment of oxyacanthine (I) with dilute hydrochloric acid, by demethylation with hydrogen bromide in acetic acid solution, dehydrative cyclization with saturated aqueous solution of hydrogen bromide, and subsequent O-methylation. The infrared spectrum (chloroform) of this free base (VI) was in complete agreement with that of natural isotrilobine. Its picrate of m. p. 188-190°, [α]_D¹⁴+200° (Me₂CO), was identified with isotrilobine picrate through infrared spectrum (KBr) (cf. Table I).