If we are to be efficient in our attempts to modify tobaccos to improve natural disease resistance, we must understand the metabolism leading to disease resistance components formed in the plant. To this end, we have studied metabolic pathways leading to pest-interactive iso-, anteiso-, and straight-chain alkyl groups of trichome exudate sugar esters formed by various tobaccos, a petunia and a tomato variety. We also examined the metabolic origin of 4-methylhexanol, an anteiso-branched alcohol of N. glutinosa flower headspace. Results indicate that carbon skeletons in all cases are formed from intermediates of branched-chain amino acid metabolism. Elongation of these skeletons in the case of tobacco and petunia iso-, anteiso, and straight-chain sugar ester acyl groups is apparently via α-ketoacid elongation. In contrast, 8-methylnonanyl, decanoyl and undecanoyl acyl groups of N. pennellii sugar esters, and N. glutinosa headspace 4-methylhexanol are apparently elongated by fatty acid synthase. These results have implications for our attempts to modify the chemical composition of tobacco gum, which will be discussed.