メギ科植物アルカロイド研究 (第27報)

ナンテンのアルカロイド その6 Domesticineの液体アンモニア中金属ナトリウムによる開裂反応

抄録

Domesticine (IV), the main phenolic base of Nandina domestica THUNB. (Japanese name “Nanten”), was submitted to cleavage reaction of its methylenedioxy group by metallic sodium in liquid ammonia, as in the case of O-methyldomesticine (I) reported in the preceding paper. As a result, only one kind of decomposed phenolic base (V) (hydrochloride: m. p. 277°(decomp.), C₁₈H₁₉O₃HCl) was obtained. This substance (V) no longer contains methylenedioxy group but has one methoxyl group. Its O-methylated compound (VIa), m. p. 122-124°, [α]_D²⁵+150.6°(MeOH), C₂₀H₂₃O₃N, was found to have three methoxyls and its infrared spectrum failed to show the presence of a phenolic hydroxyl. Its ultraviolet spectrum (Fig. 1) clearly indicated that it is an aporphine-type base and the presence of one methoxyl at 10-position was assumed.
On the other hand, synthetic procedure for dl-1, 2, 10-trimethoxyapophine (VIb) appearing in the literature was followed by the route shown in Chart 1 and the objective racemic compound (VIb), m. p. 140-141°, was obtained.
Comparison of the synthesized product (VIb) and the foregoing cleaved O-methylated base (VIa) showed that the two are entirely identical, possessing the same planar structure.
From the foregoing experimental results and the fact that methylenedioxy group undergoes one-sided cleavage to produce a new hydroxyl group, the methylenedioxy group in domesticine (IV) must have similarly undergone one-sided cleavage to produce a new phenolic hydroxyl and to form 1, 10-dihydroxy-2-methoxyaporphine (V).