抄録
About 200 alkaloids have been detected from Neotropical poison frogs of the family Dendrobatidae, some of which are used as precious tools for the neuro-pharmacological studies. Recently new cis-decahydroquinoline and 5,8-di-substituted indolizidine alkaloids were isolated from D. auratus and determined their stereochemistry through 1D-HOHAHA nmr studies. A representative cis-decahydroquinoline alkaloid 195A (5) was served as a model for subsequent conformational anlysis of cis-243(1) C_<17>H_<25>N and cis-219(2) C_<15>H <25>N. The conformational analysis through the 1D-HOHAHA studies indicated anti-coprostane(5β)type cis-juncture (Fig.1) and 2-equatorial propyl side chain (Fig.2) which had been established by x-ray crystallo-graphic analysis. For cis-243(1) the results of the 1D-HOHAHA indicated that the conformation of 8aH was axial on the β-ring [coprostane(5β)type cis-juncture](Fig.3).2-Equatorial and 8-axial conformations of the side-chains(Fig.3) were also suggested. Noe between 2H and 8'H, 12'H and 8aH supported the structure (1). In the case of the 5-methyl-8-substituted indolizidine 235B (6), rigorous confirmation of the equatorial 8-methyl group was achieved through 1D-HOHAHA studies. The new sub-classes of indolizidine and decahydroquinoline alkaloids are now presented their structure.
