Tyrosine simple tetrahydroisoquinoline alkaloids

The second synthesis pathway from L-tyrosine is to dopamine across hydro-xylation patterns and PLP activity. Dopamine is a very important compound in the synthesis of alkaloids, especially in animals. Only dopamine can be converted to another alkaloid, for example, mescaline. Anhalamine, anha-lonine, and anhalonidine can also be synthesized in this way. Like mescaline, they are typical of simple tetrahydroisoquinoline alkaloids. 

Alkaloids derived from tyrosine include phenylethylamine alkaloids, simple tetrahydroisoquinoline alkaloids, and modified benzyl tetrahydroisoquinoline alkaloids. The chemistry of Erythrina and related alkaloids from 1996 to mid-2009 has been reviewed, with a particular focus on the preparation of Erythrina alkaloids possessing an aromatic D ring [13]. 

Three 3-carboxyl substituted simple tetrahydroisoquinoline alkaloids are known from natural sources (Table 5). The compound found in Euphorbia myrsinites has been shown to originate from m-tyrosine (Muller and Schutte 1971). 

Simple tetrahydroisoquinoline alkaloids are obtained upon condensation of phenylethylamines and catecholamines with carbonyl compounds. In a subsequent Mannich-hke reaction, the biosynthetic equivalent to a Pictet-Spengler reaction, the heterocyclic ring system is established. Numerous examples of simple tetrahydroisoquinoline alkaloids have been isolated from different plant sources. Several of these tyrosine-derived secondary metabolites exhibit intriguing biological and physiological properties, due to their structural relationship to catecholamines and phenylethylamines. 

The presently known cactus alkaloids are of simple chemical constitution. They are either substituted /3-phenethylamines, evidently related to and probably derived from the naturally occurring aromatic amino acids (tyrosine, dihydroxyphenylalanine, A -methyltyrosine, etc.), or they are simple tetrahydroisoquinolines that could originate from these bases by condensation and cyclization through the action of organic compounds containing one or two carbon atoms (formaldehyde and acetaldehyde equivalents ). 

In collaboration with Dr. Margaret Roberts of the University of London, we recently learned that latex also contains miUimolar concentrations of dopamine, a fraction of which occurs in the same, relatively dense vacuoles that are rich in alkaloids (Roberts et al. 1983). Dopamine is an essential intermediate in the biogenesis of the alkaloids of the Papaveraceae (Shamma and Moniot 1978, Spenser 1969). Dopamine, which is formed from tyrosine, condenses with different carbonyl derivatives in Pic-tet-Spengler reactions to afford simple tetrahydroisoquinolines that can then give rise to a diverse array of alkaloids. Considerable evidence exists to suggest that the chirality of the tetrahydroisoquinoline alkaloids influences their transformation. It appears that morphinan alkaloids are formed from (-)-R-reticuline, whereas most other alkaloids including sanguinarine are derived from (+)-S-reticuline (Battersby et al 1965, 1975, Wilson and Coscia 1975, Borkowski et al. 1978, Brossi 1982). 

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