Rhazinilam and Quebrachamine Derivatives from Yunnan Kopsia arborea

Abstract

Three new rhazinilam-derived alkaloids, kopsiyunnanines C1, C2, and C3, and a new quebrachamine-type alkaloid, kopsiyunnanine D, which possess an unusual methoxymethyl or ethoxymethyl function, were isolated from the aerial parts of Yunnan Kopsia arborea. This is the first report of the presence of these functions in natural alkaloids. The structures and absolute configurations of the alkaloids were determined by spectroscopic methods and confirmed by semisynthesis.

Total Synthesis of Quebrachamine through Macrolactamization

“…The hemiaminal 21 was harvested by shortening the reaction time (30 min) and was converted into kopsiyunnanine D ( 2 ) under anhydrous acidic conditions. The 1 H NMR and 13 C NMR spectra of the synthetic quebrachamine and kopsiyunnanine D are consistent with the reported data 6g,3b. A nucleophilic substitution reaction between the alkali quebrachamine anion and methoxymethyl chloride (MOMCl) was applied in the previous semisynthesis of kopsiyunnanine D 3b.…”

“…Here we report our studies based on this direct approach to construction of the nine‐membered ring of quebrachimine by the lactamization of an amino acid bearing a cis ‐olefin. A recently discovered quebrachamine‐derived alkaloid, kopsiyunnanine D,3b was also prepared by the direct conversion of the indolyl carbamate to the hemiaminal ether.…”

Kopsiyunnanines F and isocondylocarpines: new tubotaiwine-type alkaloids from Yunnan Kopsia arborea

“…The leaves and fruits of Yunnan K. arborea are used to treat rheumatoid arthritis, dropsy, and tonsillitis [8]. We have previously reported the structure elucidation and semisynthesis of several unusual alkaloids isolated from the crude base of the aerial part of Yunnan K. arborea [9,10]. These alkaloids include kopsiyunnanine A, a new cytotoxic modified corynanthe-aspidospermatan-type bisindolic alkaloid; kopsiyunnanine B, a new D ring rearranged corynanthe-type oxindole alkaloid; and kopsiyunnanines C and D, which are unusual methoxymethyl or ethoxymethyl functionalized indole alkaloids.…”

Two New Aspidosperma Indole Alkaloids from Yunnan Kopsia arborea

“…20) The alkaloids were partitioned primarily by silica open column chromatography using gradient MeOH/CHCl 3 solvent system. Eburenine (3, 7.1 mg) was obtained from the fraction eluted with 10-20% MeOH/CHCl 3 .…”

“…7 formationally flexible nine-membered ring, taking together all the data mentioned above, the hydroxyl group on C-16 might have an alpha orientation. The positive Cotton effect at approximately l max 230 nm in the circular dichroism (CD) spectrum could be used to deduce the R absolute configuration at C-20 in compound 2, 20) leading to the S configuration at C-16.…”