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Two Pyrrolo[1,2‐ a ]azepine Type Alkaloids from Stemona collinsae Craib: Structure Elucidations, Relationship to Asparagamine A, and a New Biogenetic Concept of Their Formation
Author(s) -
Seger Christoph,
Mereiter Kurt,
Kaltenegger Elisabeth,
Pacher Thomas,
Greger Harald,
Hofer Otmar
Publication year - 2004
Publication title -
chemistry and biodiversity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.427
H-Index - 70
eISSN - 1612-1880
pISSN - 1612-1872
DOI - 10.1002/cbdv.200490023
Subject(s) - chemistry , asparagaceae , absolute configuration , stereochemistry , azepine , context (archaeology) , specific rotation , botany , paleontology , biology
The alkaloids 1′,2′‐didehydrostemofoline ( 2 ) and 2′‐hydroxystemofoline ( 3 ) from Stemona collinsae Craib (Stemonaceae) were studied by X‐ray crystallography and NMR spectroscopy, and they are compared with the parent compound stemofoline ( 1 ). The X‐ray analysis of the CH 2 Cl 2 solvate of 2′‐hydroxystemofoline ( 3 ) allowed the determination of the absolute configuration of this compound unequivocally, whereas optical rotation was used to infer the absolute configuration of 1′,2′‐didehydrostemofoline ( 2 ). Based on these results, it is shown that asparagamine A isolated from Asparagus racemosus Willd. (Asparagaceae) is identical to 1′,2′‐didehydrostemofoline obtained from S. collinsae Craib , and that the reported plant source of asparagamine A was most likely a Stemona species. In the context of the current investigations, a novel concept on the biosynthesis of Stemona alkaloids has been worked out and is presented here.