The biosynthesis of Sceletium alkaloids in Sceletium subvelutinum: L. Bolus

✍ Scribed by Richard B Herbert; Abdullah E Kattah

• Publisher: Elsevier Science
• Year: 1989
• Tongue: French
• Weight: 269 KB
• Volume: 30
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)80346-4

✦ Synopsis

Six sc&fium (MesembrW alkaloids (l)-(6) are identified, together with Nfl-dimethYltyramine (lo) as constihrents of SCeJ&um ~~Vehtinum. The alkaloids (l)-(6) incorporate label from radioactive tYramme (8) and 4-hYdroxYPhenYlProPionic acid (12) as expeCted; notably [3,S-3H]-4-hydroxYdihydrocinnamaldehyde las (1311 is a more efficient ab&oid Precursor than the acid (12). Preliminary evidence locates the amine (16) potentially as a key precursor for &ektiUm alkaloids; (14) is less efficiently incorporated. P]antS Of the ~Cd.dium ge!lus e&Orate a small, unique group of alkaloids exemplified by jot&&amine (4) and mesembiine (?')I. The biosynthetic origins lie in the amino acids tyrosine2 via tyramine (8) and N-methyltyramine @)I53 [ring B and attached C2-N fragment, see (l)] and phenylalanine (11)2,4, by way of 4-hydroxyphenylpropionic acid (12) and closely related compounds5 [ring A with complete loss of the side chain present in phenylalanine, see (l)]. Late stages of biosynthesis involve formation of the heterocyclic ring seen in ( ) and, as a major pathway, subsequent introduction of the second aromatic oxygen substituent seen in ( ) rather than at an earlier stage.

Intermediates more complex than (9) and ( ) have not been identified in spite of attempts to do sol; compounds of type Ar-C2-N-Cl-Ar, which are intermediates in the biosynthesis of Amaryllidaceae alkaloids, are notably not imPliCated5. We report here results which show that biosynthesis proceeds from (12) by way of the aidehyde (13) and we tentatively identify the amine (16) as a key biosynthetic intermediate in a study with the alkaloids of Sce(etium subvelutinm