Alangiside

The structure of the monoterpenoid alkaloid alangiside (115 R = H) has been confirmed by synthesis of the O-methyl ether (115 R = Me) from secologanin and 3-hydroxy-4-methoxyphenethylamine 202 the isolation of loganic acid from the same plant (Alangium lamarckii) is consistent with biosynthetic theory. 

Details have appeared of the isolation and structural elucidation of alangiside (174 R = Me, = H) (c/. Vol. 3). The location of the free phenolic hydroxy-group is based on the non-identity of the alkaloid with a sample of its isomer (174 R = H, R = Me) synthesized from secologanin/ ... 

G. Ipecoside, Alangiside, and Related Tetrahydroisoquinoline-Monoterpene Alkaloid Glucosides... 

When the last review on the ipecac alkaloids and /3-carboline congeners (1) was prepared, the chemistries of (-)-ipecoside (7) and (-)-alangiside... 

Nagakura s group (24) reported on the isolation of 54 and 55 from the methanolic extracts of the dried fruits of A. lamarckii. Since both compounds were obtainable (albeit in a low yield) from alangiside (18) by treatment with MeOH at room temperature for 9 months, they have been considered (24) to be artifacts arising from 18, the co-occurring alkaloid. 

Nagakura and co-workers (18) isolated ipecoside (7), alangiside (18), 6-0-methylipecoside (8), ipecosidic acid (10), demethylalangiside (19), neoipecoside (15), 7-O-methylneoipecoside (16), and 3,4-dehydroneoip-ecoside (17) (possibly an artifact) from the roots of C. ipecacuanha. 

Alangiside C25H31NO10 [ ]d- 105° (MeOH) was isolated from the roots, leaves, and fruit of Alangium lamarckii Thw. (Alangiaceae). However, the best source was found to be the unripe fruit. The UV spectrum... 

Glucosidase cleaved alangiside to yield D-glucose and the aglucone 27. The mass spectrum of alangiside showed a weak M+ ion at m/e 505 and a medium peak at m/e 343. The base peak in the spectrum appeared at m/e 21 A, and there were characteristic fragments of isoquinoline ions at m/e 178... 

To distinguish between these structures, a synthesis of alangiside was undertaken. Attempted condensation of 4-hydroxy-3-methoxyphenyl-ethylamine with secologanin under a variety of conditions was not successful. However, 3-hydroxy-4-methoxyphenylethylamine condensed smoothly with secologanin at pH 5.2 to afford 33 and 34. No attempts were made to obtain the individual epimers in a pure form, and the crude mixture was treated with a solution of sodium carbonate when mainly the 5/8 epimer (26) which differed from alangiside was obtained, and this on treatment with diazomethane afforded O-methylalangiside. The phenolic hydroxyl of alangiside was thus located at C-7, and structure 25 is a complete representation of the molecule (16). 

Emetine and Related Alkaloids.—A review on the ipecac alkaloids has ap-peared. (— )-Alangiside (208) is a terpenoidal lactam recently isolated from Alangium lamarckii Thw. (Alangiaceae). The structure was proven by chemical correlation with desacetylipecoside (209) (Scheme 13). ... 

Feeding experiments with [2- C]geraniol and [O-methyl- H,6- H2]loganin showed that the Cio unit of ipecoside and the C9 unit of cephaeline were of iridoid monoter-pene origin. Furthermore, [0-methyl- H,6- H2]secologanin and [3 - C]deacetylipecoside served as specific precursors for ipecoside (114) (Kapil and Brown, 1979) and alangiside (115) (Fujii and Ohba, 1983). Contrary to some earlier reports, however, deacetylisoipecoside (116) (Fig. 32.37) (witii a la-H configuration) is the precursor of cephaeline (112) and emetine (111) (Fujii and Ohba, 1983). 

Alkaloids with both types of stereochemistry at C-1 are known to occur. For example, alangiside (115) (from Alan-... 

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