Cockroaches belong to the family Blattodea, and have received special attention because they are such a nuisance in buildings. The female German cockroach Blatta germanica produces 3,11-dimethylnonacosan-2-one as a contact pheromone. From its structure it might not be seen as close to the fatty acids, but it follows easily from the consideration of branched-chain hydrocarbons. Condensation of an acetate unit and a propionate unit gives the first branching point. Three more acetate units are added before another propionate, and the chain is completed with nine more acetates. The sequence is completed by decarboxylation and


d2c. d2 d2

D2C 2

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Figure 3.29 Outline of the way in which epilachnine is biosynthesized from oleic acid and the amino-acid serine. Totally deuterated stearic acid and partially deuterated oleic acid were incorporated into deuterated epilachnine as shown. At the bottom is shown the sequence of reactions at the C-15 of oleic acid that completes the ring oxidation of a CH2 group in two stages to a ketone (Figure 3.30). This is an interesting example because the biosynthetic route is not the most obvious one expected. Usually the methyl branches are added late in the sequence, after the long straight chain has been formed, here they are known to be added at the beginning. It has been shown that this phero-mone is produced in the fat body and transported by the protein lipo-phorin to the abdominal surface.

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