Hydroaromatic intermediate

Previous studies45 have demonstrated that tyrosine and phenylalanine follow separate pathways in providing the hydroaromatic C6—C2—N unit and the aromatic C6 unit of mesembrine. In this respect mesembrine follows the pattern, already established for the biosynthesis of the structurally related Amaryllidaceae alkaloids derived from O-methylnorbelladine, e.g. haemanthamine (70). The present investigation46 followed this lead and started with a reasonable working hypothesis (Scheme 12) in which the biosynthesis proceeds via O-methylnor-belladine (68) and intermediates of the crinine type such as (75). However, feeding... 

Triteipenes an extensive group of terpenes biosynthesized from six isoprene units Apart from squa-lene, which is acyclic, most of this group are tetra- or pentacyclic hydroaromatic compounds based on the patent hydrocarbon, sterane, i.e. they are steroids Included with T. are those terpenoid natural products with fewer than 30 C-atoms, which are biosynthesized via a C30 intermediate, but with subsequent loss of one or more C atoms Addition of extra C atoms and incorporation of heteroatoms are also possible, e.g. 

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