Thief ants pyrrolizidine

A related oxime 304 was prepared for the total synthesis of 305, an unusual pyrrolizidine alkaloid isolated from the venom of a variety of thief ant... 

The venomous constituent of the cryptic thief ant, Solenopsis xenovenenum, has been identified as the 3-heptyl-5-methylpyrrolizidine (50) from its mass spectrum and the fact that a related pyrrolidine (51) has been isolated from another species of ant.47 This is the first reported occurrence of a 3,5-dialkyl-pyrrolizidine, and its structure was confirmed by synthesis. Reductive amination of the known triketone (52) with sodium cyanoborohydride and ammonium acetate gave a mixture of four isomers of 3-heptyl-5-methylpyrrolizidine, which were separated by preparative g.l.c. The stereochemistry of the ring-junction of each isomer was established from its i.r. and n.m.r. spectra. 

Disubstituted pyrrolizidines were first discovered in Nature as constituents from ants (121). The structure of (5Z,8 )-3-heptyl-5-methyl-pyrrolizidine from thief ant (Solenopsis xenovenenum) venom proved identical with the amphibian pyrrolizidine 5Z,8 -223H (Fig. 10). Other pyrrolizidines from ants include (5 ,8Z)-3,5-di(5-hexenyl)pyrrolizidine, (5Z,8 )-3-methyl-5-(8-nonenyl)pyrrolizidine, and (5 , 8Z )-3-(8-nonenyl)-... 

Pyrrolizidine alkaloids also have been found in amphibians. Certain of these amphibian alkaloids also occur in insects. For example, the venom of the thief ant, Solenopsis xenovenenum, is an amphibian pyrrolizidine (Daly et al., 1993). 

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