Strychnan and Secoangustilobine A Type Alkaloids from Alstonia spatulata. Revision of the C-20 Configuration of Scholaricine

Abstract

A total of 25 alkaloids were isolated from the leaf and stem-bark extracts of Alstonia spatulata, of which five are new alkaloids of the strychnan type (alstolucines A-E, 1-5) and the other, a new alkaloid of the secoangustilobine A type (alstolobine A, 6). The structures of these alkaloids were established using NMR and MS analysis and, in the case of alstolucine B (2), also confirmed by X-ray diffraction analysis. A reinvestigation of the stereochemical assignment of scholaricine (13) by NMR and X-ray analyses indicated that the configuration at C-20 required revision. Alkaloids 1, 2, 6, 7, 9, 10, and 13 reversed multidrug resistance in vincristine-resistant KB cells.

A sequential cycloaddition strategy for the synthesis of Alsmaphorazine B traces a path through a family of Alstonia alkaloids

“…NaBH 4 reduction of alstolucine B ( 46 ) provided echitamidine ( 64 ), [27,33b,d,i,j,52] while the similar reduction of alstolucine F ( 56 ) in the presence of CeCl 3 •7H 2 O led to demethylalstogustine ( 65 ). [33b,d,i,j,34,53] Simple acylation of demethylalstogustine with ethyl chloroformate provided alstolucine A ( 66 ). [25,33i,j] …”

Synthesis and Biological Evaluation of Pentacyclic Strychnos Alkaloids as Selective Modulators of the ABCC10 (MRP7) Efflux Pump

“…The optical rotation for synthetic 3 was [α] D 20 −307 ( c 0.29, CHCl 3 ), whereas the reported value was [α] D 20 −371 ( c 0.15, CHCl 3 ). 27 …”

“… 25 , 26 In 2010, Kam and co-workers isolated novel pentacyclic Strychnos alkaloids alstolucines A–F, from Alstonia spatulata (Figure 1 ). 27 In addition, they were evaluated for their ability to resensitize vincristine-resistant KB cells, which overexpress P-gp. Structurally, the alstolucines are closely related to the classical Strychnos alkaloid akuammicine ( 1 ), which we have prepared by total synthesis in both racemic 28 and asymmetric form.…”

Three New Monoterpenoid Indole Alkaloids from Ervatamia pandacaqui

“…Compound 6 had the molecular formula of C 20 H 22 N 2 O 4 , as deduced from its HR-ESI-MS at m/z 355.1658 ([M + H] + ), 16 mass units higher than that of 12-hydroxyakuammicine (7). [17] Detailed examination of 1D-and 2D-NMR spectra of 6 and comparison with those of 7 indicated that compound 6 was readily identified as 12-hydroxyakuammicine N(4)-oxide, which was confirmed by the characteristic downfield shifts of the carbon resonances for C-3 (d(C) 79.7), C-5 (d(C) 70.6), and C-21 (d(C) 74.1). The structure of 6 was thus characterized as 12-hydroxyakuammicine N(4)-oxide.…”

“…[6 -9] The plants Ervatamia pandacaqui are mainly distributed in southern Taiwan Province, which are used for the treatment of bellyache, headache, and hypertension in Chinese folk medicine. As part of searching for structurally unique and biologically interesting MIAs from the genus Ervatamia, [10 -13] three new monoterpenoid indole alkaloids, ervapandine A (1), (3R)-hydroxyibogaine (3), 12-hydroxyakuammicine N (4)-oxide (6), and four known compounds 19-epi-voacristine (2), [14] ibogaine (4), [15] taberdivarine I (5), [16] and 12-hydroxyakuamicine (7), [17] were isolated from the leaves and twigs of E. pandacaqui. The new alkaloids were elucidated by spectroscopic methods and sugar hydrolysis experiment, and the known ones were identified by comparing their spectroscopic data with those reported in the literature.…”