The Biosynthesis of Polyacetylenes

The principal acetylenic metabolites of the basidiomycete B. 841 (probably a Poria sp.) are known to be the hydroxy acids nemotinic acid (I) and odyssic acid (II), together with derivatives such as the corresponding lactones (Bu'Lock, Jones & Leeming, 1955, 1957). Acetylenic compounds of various kinds are now known to be relatively common constituents of certain groups of plants and fungi, and it is natural that interest should be felt in problems of their origin and their relationship to more conventional metabolites. In such a connexion the polyacetylenes from B. 841 form an apt group for further study, since they are produced fairly rapidly and in good yields (up to 1 mg./ml.) from culture media of simple constitution and, as all the compounds have strong absorption maxima at substantially the same wavelengths, their total amount is readily determined. The structures of (I) and (II) are not symmetrical so that isotopic studies are not likely to be vitiated by spurious randomization of labelling, a situation which would prevent comparable studies in many other polyacetylene-producing fungi; moreover, as is shown in this paper, the molecules of (I) and (II) are derived entirely from a single metabolic intermediate, a consideration which is bound to simplify the relationship between their synthesis and other metabolic processes in the fungus. The gross characteristics of the formation of polyacetylenes from glucose in B. 841 have already been established (Bu'Lock & Leadbeater, 1956). It was shown that they are probably formed from an intermediate in normal glucose breakdown, and that the extent to which metabolized glucose carbon was diverted into polyacetylene synthesis was diminished during active growth of the fungus and could be increased by omitting essential growth factors from the nutrient medium. The present work is concerned with the identification of the intermediate from which the carbon atoms of (I) and (II) are derived.