Yaf

indolizidines

a ketoindolizidine

tetraponerines pyrrolizidines a ketoindolizidine

Figure 9.10 More complex alkaloids from ants. The indolizidines where R is butyl, hexyl and 3-hexenyl have been known from the venom o/Monomorium pharaonis, pharaoh's ant, for some time. The 2-heptyl-8-methyl-pyrrolizidine is from a Solenopsis ant. The keto-indolizidine is from an African Myrmicaria ant. There are eight of the tetraponerines from Tetraponera species from New Guinea into two groups, designated 6,6,5 and 5,6,5 by the size of their three rings (Figure 9.10). The biosynthesis of the tetraponerines has been studied using sodium [l-14C]-acetate and [2-14C]-acetate, [l,4-14C]putrescine dihydrochloride and l-glutamic acid, y-aminobutyric acid and l-ornithine, all uniformly labelled with 14C. Both groups were shown to have a mixed biosynthetic origin, from an amino-acid and a chain of acetate units, as shown in Figure 9.11. Note that y-aminobutyric acid, produced by decarboxylation of glutamic acid is not a protein amino-acid, but is another of the physiologically active amines. It is a potent neurotransmitter. Topical application of a tetraponerine mixture to Myrmica ants indicated a toxicity ten times greater than that of nicotine.

hooc cooh hzi\l h2nx ,cooh hooc cooh hzi\l h2nx ,cooh

nh2 cooh Y-aminobutyric acid h h

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