New Morphinane and Hasubanane Alkaloids from Stephania cepharantha

Abstract

Six morphinane alkaloids, cephasamine (3), cephakicine (4), tannagine (6), 14-episinomenine (7), FK-3000 (8), and sinoacutine (9), and five hasubanane alkaloids, cephatonine (5), cepharamine (10), aknadinine (11), aknadicine (12), and aknadilactam (13), were isolated from the tuber of Stephania cepharantha Hayata (Menispermaceae) cultivated in Japan. Three of these (3−5) were new alkaloids. Structures were spectroscopically determined by comparison of their 1H and 13C NMR data with that of cephamonine (1), cephamuline (2), and other known alkaloids (6−13).

Model Studies Towards Stephaoxocanes: Construction of the 2‐Oxa‐4‐aza‐ phenalene Core of Stephaoxocanidine and Eletefine

“…0.7:1) in 90 % yield, which was equilibrated to the most stable isomer (E)-7 (E/Z Ͼ 20:1) with thiophenol in toluene at 80°C under AIBN promotion, in almost quantitative yield. The stereochemical assignment of (E)-7 was supported by 1 15.6 Hz), especially differential NOE spectroscopy. The H-2 proton coupled to the methyl group (J ϭ 6.6 Hz) showed a signal enhancement of 14 % upon irradiation of its aromatic neighbor (H-3Ј), whereas irradiation of H-2 produced a 6 % increase in the size of H-3Ј doublet.…”

“…The novel tetracyclic stephaoxocane skeleton 1a is common to a small family of isoquinoline alkaloids, revealed in recent years through the work of Japanese, [1,2] Chinese [3,4] and Brazilian [5] research groups. To date, the isolation of only five stephaoxocanes (1bϪf) has been reported, their source being plants of the Menispermaceae family employed in folk medicine.…”

Synthesis of the Carbon Framework of the Stephaoxocanes Employing a Sequential RCM/Pomeranz–Fritsch Approach

“…[1] Recent studies on Chinese, Japanese and Brazilian Menispermaceae unveiled a small and structurally unusual family of isoquinoline-type natural products carrying an oxocane ring, for which the name stephaoxocanes was coined. [2] The same designation was proposed for their common tetracyclic ring system 1a ( Figure 1). …”

Short, Enantioselective Total Syntheses of (−)‐8‐Demethoxyrunanine and (−)‐Cepharatines A, C, and D

“…[7] The structural similarities between the hasubanans and the cepharatines have led to the hypothesis that both arise biosynthetically from common precursors. For example, 3, 7, and 8 are proposed to derive from sinoacutine (11), [7,8] a compound related, although of the opposite enantiomeric series, to morphine. Indeed, owing to the topographical similarities between compounds 1-5 and morphine, there is speculation that the unnatural enantiomers of the hasubanans may exhibit analgesic properties.…”