Late stages in the biosynthesis of ipecac alkaloids - cephaeline, emetine and psychotrine in Alangium lamarckii Thw. (Alangiaceae)

Abstract

The bioconversion of tyrosine, dopamine, N- desacetylisoipecoside (15) and N- desacetylipecoside (16) into cephaeline (2), emetine (1), and psychotrine (3) into Alangium lamarckii Thw. (Alangiaceae) plant has been studied. Stereospecific incorporation of N- desacetylisoipecoside (15) into 1,2 and 3 has been demonstrated. Further it has been shown that reduction of C1’ – C2’ takes place after O-methylation of psychotrine (3). Feeding results further showed that cephaeline was poorly metabolized in the plants to form psychotrine (3) thus demonstrating that dehydrogenation of C1’ – C2’ does not take place. The efficient incorporation of cephaeline into emetine (1) further showed that O- methylation is the terminal step in the biosynthesis of emetine. Emetine (1) was poorly metabolized by the plants to form cephaeline (2) and psychotrine (3). The experiments thus demonstrated that dehydrogenation and O-demethylation of emetine (1) does not occur to give cephaeline (2) and psychotrine (3). Scientific World, Vol. 10, No. 10, July 2012 p24-28 DOI: http://dx.doi.org/10.3126/sw.v10i10.6857

Tritium-labelled alkaloids: Synthesis and applications

“…Essentially, the same method (sodium borotritide reduction‐mild oxidation) was used to prepare structurally similar [ 3 H]coptisine but in this case the final central ring oxidation was performed enzymatically . Closely related analogue tetrahydropalmatine was tritium labelled by means of a bromination‐catalytic tritium dehalogenation approach, and cephaeline was tritiated by a general exchange method using tritiated water …”

“…64 Closely related analogue tetrahydropalmatine was tritium labelled by means of a bromination-catalytic tritium dehalogenation approach, 65 and cephaeline was tritiated by a general exchange method using tritiated water. 66 Noscapine is a benzyl isoquinoline alkaloid produced by the opium poppy but also devoid of any analgesic properties. It has been tritium labelled by means of a general exchange process 67 and used in receptor binding experiments to study its antitussive action.…”

Enantiodivergent Synthesis of Benzoquinolizidinones from L-Glutamic Acid

“…Many of these alkaloids possess interesting biological activities [ 1 , 2 , 3 ]. For examples, protoemetinol ( 1 ) is a natural tetrahydroisoquinoline alkaloid which is found as a substructure or biosynthetic precursor of other biologically active alkaloids such as emetine ( 2 ), an anti-amoebic substance which also inhibits breast tumor growth [ 4 , 5 ]. Tetrabenazine ( 3 ) is a synthetic drug for treatment of motor function disorder due to Huntington’s disease [ 6 ].…”