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cooch3

methyl 4-methylpyrrole-2-carboxylate

Figure 9.16 A suggested route to the pyrrole trail pheromone of some leaf-cutting ants of the initially formed keto-group to an alcohol and possible dehydration to the unsaturated examples. This suggests the possible biosynthetic route. The presence of the aldol dimer of isopentanal in the same secretion offers support for this suggestion. Some alkylpyrazines are of the 2,3-dimethyl type, with a less obvious biosynthetic origin. An example is 2,3-dimethyl-5-(2'-methylpropyl)pyrazine (Figure 9.15), the trail pheromone of the ant Eutetramorium mocquerysi from Madagascar.

Methyl 4-methylpyrrole-2-carboxylate (Figure 9.16) is non-basic. It is the trail pheromone of some leaf-cutting ants. It is probably made from leucine by oxidation and cyclization.

The subject of alkaloids is one with no clear boundaries. Other compounds already discussed, indole and skatole (Figure 8.5, non-basic), actinidine, a defensive compound of several species of rove beetles

(Figure 6.11), pterins and ommachromes, could be included under this heading, while some neutral plant amides like colchicine are always considered among alkaloids.

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