Of cephalotaxus alkaloids

It was noted that chromatography of Cephalotaxus alkaloid fractions over neutral alumina resulted in considerable losses (111). Further elution with dilute aqueous acetic acid resulted in the isolation of a new alkaloid, desmethylcephalotaxinone ([a]D +2.3°). The IR spectrum of this alkaloid was consistent with the presence of a vinylic hydroxyl group (3520 cm-1) and a conjugated carbonyl group (1690 cm 1). The NMR spectrum obtained in deuterochloroform contained features of the cephalotaxine structure, but included a singlet attributable to an isolated methylene (<5 2.54 ppm). In DMSO-c/6 this resonance appeared as an AB quartet. Acetylation... 

Spencer GF, Plattner RD, Powell RG. Quantitative gas chromatography and gas chromatography-mass spectrometry of Cephalotaxus alkaloids. J. Chromatogr. 1976 120 335-341. Grem JL, Cheson BD, King SA, Leyland-Jones B, Suffness M. Cephalotaxine esters antileukemic advance or therapeutic failure J. Natl. Cancer Inst. 1988 80 1095-1103. 

EXPERIMENTAL CONDITIONS USED FOR GAS CHROMATOGRAPHY OF cephalotaxus ALKALOIDS... 

A lucid introduction to this group has been published as part of a general text on the chemistry of alkaloids.1 The relatively small and novel group of Cephalotaxus alkaloids which show inhibitory activity against experimental lymphoid leukemia has been briefly reviewed in a volume dedicated primarily to the interests of medicinal chemists.2... 

Patents on Production of Cephalotaxus Alkaloids by Means of Plant Cell... 

Medicinal Uses of Amaryllidaceae Alkaloids Mesembryanthemum and Sceletium Alkaloids Cephalotaxus and Homoerythrina Alkaloids Biosynthesis of Cephalotaxus Alkaloids Biosynthesis of Homoerythrina Alkaloids Systematic Value of Cephalotaxus and Homoerythrina Alkaloids... 

Biosynthetic studies of Cephalotaxus alkaloids indicate that ring A of the cephalotaxine molecule is derived from tyrosine, and rings C and D are derived from phenylalanine. 

Fig. 33.11. Proposed biogenesis of the acid portion of Cephalotaxus alkaloids (modified from Huang and Xue, 1984 used with permission of the copyright owner. Academic Press, Orlando, FL).

There are two groups of Cephalotaxus alkaloids the cephalotaxine - har-ringtonine group and the group represented by alkaloids II and III. The latter are often called homoerythrinan alkaloids. 

A possible pathway of the biosynthesis of Cephalotaxus alkaloids is shown in Fig. 5.2.13 (120). A similarity has been pointed out between this scheme and that of Erythrina alkaloids (Sect. 5.2.2.5.T). The starting open-ring intermediate in the present case is phenethylisoquinoline, instead of benzylisoquinoline for the Erythrina alkaloids. On this basis, homoerythrinan-type alkaloids are also called phenethylisoquinoline-type alkaloids. 

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