3.5- Disubstituted indolizidines absolute configuration

Fig. II. Structures of 3,5-disubstituted indolizidines from amphibians. The absolute configuration of natural levorotatory (S ,9 )-223AB, (5 .9 )-239AB, and (5 .9 )-239CD, are known. Natural dextrorotatory (S ,9 )-195B has the opposite absolute configuration as that shown above U29a). The configurational nomenclature is based on that introduced by Sonnet et at. (122), where the H-S and H-9 configurations are related to that of H-3 and are either cis (Z) or trans ( ).

Fig. 13. Structures of other S,8-disubstituted indolizidines from amphibians. Most have been characterized from ranid frogs of the genus Mantella (73). Absolute configurations are unknown. All have the S,9Z configuration. The configuration at the 8 position could not be determined from FTIR spectra.

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