Tetraponerine ants

Some ants make products reminiscent of the coccinellid alkaloids. Three indolizidines are known from the venom gland of Monomorium pharaonis (Figure 9.10), and a pyrrolizidine from a Solenopsis ant has been known for some time. They would appear to be formed from polyketides or fatty acids as in the case of the coccinellines. More pyr-rolizidines and indolizidines with two alkyl and alkenyl groups have been found in Monomorium and Solenopsis species. Tetraponerine ants smear the venom of their poison glands onto prey. The venom consists of tricyclic alkaloids called tetraponerines (Figure 9.10). They are divided... 

Four members of the tetraponerine family (the major constituents of the contact poison of the New Guinean ant Tetraponera sp.) were prepared by RRM methods [156]. The key step leading to tetraponerine T7 (374) from the readily available cyclopentene precursor 372 is shown in Scheme 72. When compound 372 was exposed to catalyst A in the presence of ethylene, the desired ROM-RCM sequence proceeded smoothly to furnish heterocycle 373 with complete conversion, whereas the corresponding di-nosyl (2-nitrophenylsulfonyl)-protected analog of 372 led only to a 1 2 equilibrium mixture of starting material and RRM product. 

Since the discovery of tetraponerine-8 in 1987 by Braekman et al. [195] the tetraponerines, the defensive alkaloids of ants of the genus Tetraponera, have been the target of considerable synthetic efforts and have served to demonstrate the utility of various synthetic methodologies [114]. Recently a few further syntheses of these unusual tricyclic alkaloids have been reported. 

Another example of a natural product that we synthesised using a ROM-RCM sequence are tetraponerines.23 Tetraponerines (T1-T8) (Figure 6) were isolated from the venom of the New Guinean ant Tetraponera sp.24 These alkaloids represent the major constituents of the contact poison and contaminated enemies immediately show symptoms of nerve poisoning. 

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 Soienopsis ant. The keto-indolizidine is from an African Myrmicaria ant. There are eight of the tetraponerines from Tetraponera species from New Guinea...

Figure 9.11 The formation of two examples of the tetraponerines from ants. Glutamic acid, ornithine and y-aminobutyric acid uniformly labelled with 0, sodium acetate labelled in C-1 and C-2 with Q and [l,4- C]putrescine were all used to show the synthesis is as shown...

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