Figure 1.

Subclasses of diastereoisomeric 5,8-disubstituted alkaloids. The absolute stereochemistry of 5,9Z-203A and 5,9Z-235B' are as shown, while the structure shown for 5,9E-259B is tentative as postulated based on mass and FTIR spectra.[2] Almost all of the 5,8-disubstituted indolizidines detected in frog skin extracts have proved to be the 5,9Z isomers.[2]