Cephalotaxus alkaloids biosynthesis

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... 

Cephalotaxus Alkaloids.—Preliminary results indicate that the homo-Erythrina alkaloid schelhammeridine (52) derives from phenylalanine and tyrosine by way of a phenethylisoquinoline precursor [as (53)].52 Previous evidence for the biosynthesis of the related alkaloid cephalotaxine (54), obtained with tyrosine labelled in the side-chain, has indicated a different pathway which involves two molecules of this amino-acid.53 Recently, however, tyrosine labelled in the aromatic ring was examined as a cephalotaxine precursor and was found54 to label ring A of (54) almost exclusively, i.e. only one unit of tyrosine is used for biosynthesis. This is obviously inconsistent with the previous evidence and the early incorporations are... 

A review on Erythrina and related alkaloids covering the literature from Noventer 1966 to the end of May 1979 has appeared it sutnnarizes the work published on isolation, structure determination, biosynthesis, synthesis and pharmacolc of Erythrina, Hcmoerythrina, and Cephalotaxus alkaloids, and the... 

Dibenz[i7,/]azecines (see Cephalotaxus alkaloids) have been discussed as intermediates (formula II in the biosynthesis of cephalotaxin) of homoerythrinan-Cephalotaxus 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. 

Parry R J, Chang M N T, Schwab J M, Foxman B M 1980 Biosynthesis of the Cephalotaxus alkaloids. Investigation of the early and late stages of cephalotaxine biosynthesis. J Am Chem Soc 102 1099-1111... 

Fig. 5.2.13. Proposed biosynthesis of Cephalotaxus and homoerythrina-type alkaloids...

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