Coclaurine

In addition to the foregoing benzylwoquinoline alkaloids all derived from Papauer spp, two other members of the group, coclaurine and iso-coclaurine are described in the bisbenzylisoquinoline group (p. 349) with which they are naturally associated. 

In the following descriptions of coclaurine and the chief bisbenzyh so-quinoline alkaloids, the numbers in brackets after the names of the alkaloids refer to the numbered items in the foregoing list. 

Coclaurine is of special interest since worcoclaurine (I MeO HO) can be regarded as the parent substance from which by ether formation the series of bisbenzylisoquinoline alkaloids can arise. Thus, the dauricine type of alkaloid may be formed by a single ether linkage between the 4 -hydroxyl of one woreoclaurine molecule and a hydrogen atom ortho to the 4 -hydroxyl of a second molecule. 

Alkaloids of the Menispermaceae Coclaurine, Dauricine, Magnoline, Tetrandrine, Bebeerine, etc.. ... 

Choi, K. B., Morishige, T., Shitan, N., Yazaki, K. and Sato, F. 2002. Molecular cloning and characterization of coclaurine N-methyl transferase from cultured cells of Coptis japonica. Journal of Biological Chemistry, 277(1) 830-835. 

Nelumbium nelumbo Druce. Lian Zi Xin (Lotus) (plumule) Liensinine, isoliensinine, neferine, lotusine, methyl-corypalline, demethyl-coclaurine.33 Tranquilizing and antihypertensive. 

The majority of recent biosynthetic studies on bisbenzylisoquinoline alkaloids has been done by Bhakuni and co-workers, using feeding of isotopically labeled precursors to alkaloid-producing plants this work has been reviewed (339,340). In this manner, several of these alkaloids were shown to be derived by coupling of coclaurine or V-methylcoclaurine units the thalicarpine family of alkaloids, however, is formed from two (S)-reticuline (430a) units (148,339). 

Stephania glabra (Roxb.) was shown to produce cycleanine (112) and N-desmethylcycleanine (129) via dimerization of both (R)-lV-methylcoclaurine (69) and (R)-coclaurine (although the racemic form of the latter was used in these experiments). The plant was proven to utilize L-tyrosine to biosynthesize the intermediate Af-methylcoclaurine. The exact sequence of dimerization-Af-meth-ylation/N-demethylation has not yet been determined (346). 

Bisbenzylisoquinoline Alkaloids.—The skeleton of coclaurine (46) is one which serves as a common starting point for the biosynthesis of several bisbenzylisoquinoline alkaloids (cf. Vol. 10, p. 16). Coclaurine (46) and JV-methyl-coclaurine (47) have recently been found to be precursors also for isotetrandrine... 

Fig. 18 Reconstructed isoquinoline alkaloid biosynthetic pathway in microbes (E. coli and S. cerevisiae) [120]. Accession numbers of the genes can be taken from Gene Bank. C3,4-DHPA-A 3,4-dihydroxyphenylacetaldehyde NCS norcoclaurine synthase 60MT 6-0-methyltransferase CNMT coclaurine-/V-mcthyltransferase 4 OMT 4 -0-methyltransferase BBE berberine bridge enzyme NMT /V-methyltransferase)...

The three cDNAs of norcoclaurine-6-O-methyltransferase, coclaurine-AA methyltransferase and 3 -hydroxy-AAmethylcoclaurine 4,-<9-methyltransferase converting (R, S)-norlaudanosoline into (R, Sj-reticuline with a 5-10% yield... 

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