Isomerization of Dimeric 2,9-Disubstituted1-Oxaquinolizidine Alkaloids and Structural Revision of Araguspongines B and E, Isolated from a Marine Sponge of Xestospongia Sp.
摘要:
Isomerization reaction of araguspongines B (1), D (2), and E (3) having dimeric 2,9-disubstituted 1-oxaquinolizidine moiety was studied in detail. Conformational aspects of 1, 2, and 3 were also analyzed on the basis of NMR and X-ray crystallographic analysis. The C-9 stereochemistry of 1 and 3 was revised.