Strictosidine, the common precursor for monoterpenoid indole alkaloids with 3 α and 3 β configuration

Recently we reported that strictosidine (l> is the key intermediate in the formation of the three classes (ASDidOf3DeIm5, Iboga, Corynanthe) of monoterpenoid indole alkaloids In Catharanthus roseus and a variety of other plant species in cell culture using in vivo and in vitro techniques"2. These results were independently confirmed In Manchester 394 and subsequently also Scott et a1.5 were able to confirm the precursor role of (1) using Catharanthus material. All these results are in accord with reports on the biosynthesis of an alkaloid of taxonomically distant origin, camptothecln, for which strictosidine la&am6 was previously found to be a precursor, and recently7 also (1). The key intermediate in the biosynthesis of the majority of mono-terpenoid alkaloids is therefore (1) with 3 a (2) configuration, rather than vincoside (2) with 3 13 (lX> configuration as had previously been assumeda. However, a generalization of this precursor function of (1

(S)norlaudanosoline synthase. the first enzyme in the benzylisoquinoline biosynthetic pathway

1. introduction Isoquinoline alkaloids form the largest group of alkaloids in the plant kingdom. Numerous publications deal with aspects of the biosynthesis of these compounds in vivo [ 11, while isoquinoline biosynthesis at the cell-free level had hardly been touched [Z]. The initial reaction in isoquinoline biosynthesis has long [3] been assumed to be a condensation of two aromatic units, both derived from tyrosine, namely dopamine and 3,4-d~ydroxyphenylacet~dehyde [4]. This scheme was later modified [5] where it was reported that condensation of dopamine with 3,4-dihydroxyphenylpyruvate would lead to an amino acid, norlaudanosoline-l-carboxylic acid, which in turn, by decarboxylation, would yield norlaudanosoline