G. Subramaniam

Alkaloids from Kopsia dasyrachis

Abstract A total of 32 alkaloids were obtained from the stem extract of Kopsia dasyrachis,of which ten are new, viz., kopsiflorine N (4)-oxide, 11-methoxykopsilongine N (4)-oxide,kopsifine, decarbomethoxykopsifine, kopsinarine, 11,12-methylenedioxykopsine, dasyrachine,rhazinicine, (+)-19 (R)-hydroxyeburnamine and (−)-19 (R)-hydroxyisoeburnamine.

Reversal of multidrug resistance (MDR) by aspidofractinine-type indole alkaloids.

A series of indole alkaloids of the aspidofractinine-type was assessed for their potential in reversing MDR in vincristine-resistant KB cells. Of the compounds tested, kopsiflorine, kopsamine, pleiocarpine, 11-methoxykopsilongine, lahadinine A and N-methoxycarbonyl-11,12-methylenedioxy-delta 16,17-kopsinine were found to show appreciable activity.

Rhazinal, a Formylrhazinilam Derivative from a Malayan Kopsia

Abstract A new rhazinilam-type alkaloid, rhazinal, was obtained from the stem extract of Kopsia teoi and its structure established by spectral analysis.

Mersinines A and B and mersiloscine, novel quinolinic alkaloids from Kopsia

Abstract Three novel quinolinic alkaloids, viz., mersinines A and B and mersiloscine, were obtained from a Malayan Kopsia species and the structures established by spectroscopic analysis.

Oxo-Derivatives of Kopsine- and Rhazinilam-Type Alkaloids from a North Borneo Kopsia

Abstract Two new alkaloids, kopsifine and rhazinicine, which are oxo-derivatives of kopsine and rhazinilam respectively, were obtained from the stem extract of Kopsia dasyrachis and their structures were established by spectral methods.

17-α-Hydroxy-Δ14,15-kopsinine and a bisindole alkaloid from Kopsia teoi

Abstract The structure of 17-α-hydroxy-Δ14,15-kopsinine has been confirmed by a detailed NMR analysis. A bisindole alkaloid was obtained from the leaf extract of Kopsia teoi and its structure established by spectral methods.

Danuphylline, a novel pentacyclic indole from Kopsia

Abstract A novel pentacyclic indole alkaloid, danuphylline, was obtained from the leaf-extract of Kopsia dasyrachis and its structure elucidated by spectral analysis.

19(R)-Hydroxyeburnamine and 19(R)-Hydroxy-Isoeburnamine from Kopsia Dasyrachis

Abstract Two new alkaloids, (+)-19(R)-hydroxyeburnamine and (-)-19(R)-hydroxy-isoeburnamine, in addition to the known eburnane compounds, (+)-eburnamonine and (+)-isoeburnamine, and the bisindole, kopsoffinol, were obtained from the stem extract of Kopsia dasyrachis and their structures were established by spectral methods and X-ray analysis.