Biogenesis of Nonacosan-15-one in Brassica oleracea : Dual Mechanisms in the Synthesis of Long-chain Compounds

Abstract

THE Channon–Chibnall mechanism¹ for the biogenesis of long-chain ketones of the form R·CO·R from 2R·CO₂H affords a natural explanation of the frequent location of the carbonyl group at the midpoint of the chain. The explanation has been accepted by most biochemists, especially after this route was proved, by the ¹⁴C tracer method, to be followed in the biosynthesis of corynomycolic acid (I)². A natural corollary has been the assumption that long-chain hydrocarbons, such as hentriacontane, are biogenetically derived by reduction processes from ketones made by the Channon–Chibnall mechanism. It should be noted, however, that the naturally occurring long-chain hydrocarbons do not obey the implied rule in a very satisfactory way. Nonacosane, probably the most widely distributed hydrocarbon of all, is accompanied in many petroleums by the normal C₂₇ and C₃₁ alkanes which are each more abundant than neighbouring hydrocarbons with an even number of carbon atoms, but occur in only about half the quantity of nonacosane.