Involvement of Cathenamine in the Formation of N–Analogues of Indole Alkaloids

Abstract

Cathenamine (12), vallesiachotamine (14a), isovallesiachotamine (14b), 22–N–tetrahydroalstonine (17), (19–α–methyl)–(16b) and (19–β–methyl)–18–deoxy–15,22–dihydro–3–iso–cadamine(16a) were isolated from incubations of cell–free extracts from Rauwolfia verticillata cell suspension cultures. The formation of the–N–analogues (16a), (16b) and (17) in the presence of (NH₄)₂SO₄ in these incubations indicated that the isolation of alkaloids containing additional N–atoms should be suspected of being artifacts and not necessarily biosynthetic intermediates or products. However, the formation of (16a) and (16b) both from tryptamine (1) and secologanin (2) as well as cathenamine (12) showed that the pathway of cathenamine (12) formation is reversible and gave indirect evidence for the presence in the pathway of the „open” aglycone (5) obtained upon hydrolysis of the glucoside strictosidine (3).

Key Word Index

Rauwolfia verticillata - Apocynaceae - Cell Suspension Cultures - Biosynthesis - Indole Alkaloids