Ergot alkaloids constitution

Ergot alkaloids, 517 characteristics, 519 constitution, 525 dihydro-derivatives, 532 hydrolytic products, 526 pharmacological action, 533 relative sympathicolytic activities, 535... 

The SRN1 mechanism represents an excellent alternative to accomplishing the following intramolecular cyclization reaction (Scheme 10.42), which constitutes one of the steps in the synthesis of rugulovasines A and B (20, a-H and P-H), novel structures within the family of ergot alkaloids [58]. 

In P. semperviva it has been demonstrated that tryptophan is a precursor of psilocybin (93a). It was simultaneously suggested that a similar oxidation of tryptophan or a tryptophan metabolite at the 4-position constitutes an important intermediate stage in the biosynthesis of the ergot alkaloids from tryptophan. 

In all hypotheses relating to the biogenesis of the ergoline-lysergic acid moiety of ergot alkaloids, it was assumed that tryptophan constituted a main structural element. This assumption was later shown by experiment to be correct. 

Until now no process was known which allows the physiologically practically inactive lysergic acid to be linked with a basic residue, such as an amino-alcohol or an amino acid, in order to prepare compounds of the type of ergot alkaloids. This was primarily due to the fact that lysergic acid was very difficult to prepare, as it was only obtainable as a degradation product from ergot alkaloids and because its constitution was unknown. 

Ergotamine and ergotoxine (now known to be a group of three alkaloids) constitute the water-insoluble fraction of ergot. Ergotamine has a high affinity for a-adrenoceptors, but it produces a lower response than does NE (i.e., it can be viewed as a partial agonist). 

This section is concerned with diverse metabolites based on tryptophan (some also appear above). A large group is constituted by the ergot alkaloids. 

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