Beitrag zur absoluten Konfiguration der Spermin‐Alkaloide O ‐Methylorantin und Aphelandrin. 175. Mitteilung über organische Naturstoffe

Contribution to the Absolute Configuration of the Spermine Alkaloids O ‐Methylorantine and Aphelandrine The absolute configuration of the spermine alkaloid O ‐methylorantine (1) isolated from Chaenorhinum minus (L.) W ILLK. ET L GE . and Ch. villosum (L.) W ILLK. ET L GE . was determined. Besides the difference in the substitution at C(31) (OCH 3 versus OH) the constitution of 1 and aphelandrine (2) [6] is the same. This was established by spectroscopic evidence, by isomerization reactions of 2 , orantine (4) and their derivatives ( Scheme 2 ), and by degradation reactions of 1 and 4 , respectively. The methyl ether 1 of orantine (4) , the latter prepared by base catalyzed isomerization from aphelandrine (2) , is in all respects identical with the natural O ‐methylorantine (1). Orantine (4) is identical (UV., CD., 1 H‐NMR. and TLC. evidence) with ephedradine A, recently isolated by Hikino et al. [8], who determined the absolute configuration of ephedradine A by X‐ray analysis. The absolute configuration of aphelandrine (2) was related to the one of 4 by chemical degradation.