The biosynthesis of polyisoprenoids

To a chemist, a natural product may be a structural problem, an objective for synthesis, an exhibitor of chemical and physical properties, or perhaps mere raw material. The tendency to regard it as a sample of the living organism's synthetic power is more recent, and experimental investigation of that power is more recent still. Such experiments depend on the use of isotopic tracers, and they alter the traditional objectives and values in an interesting manner. Thus, before isolation of a natural product, the organism must be induced to make it from an isotopically labelled precursor; chemical degradations are directed not to elucidation of structure but to unambiguous location of labelled atoms; and complicated and novel syntheses may be needed to prepare a specifically-labelled intermediate. And, eventually, the student of biosynthesis may find himself looking on certain large classes of natural products not-as he ought to do-as rich collections of beautiful chemistry, but as conglomerations too variable to be of great importance in the fundamental chemistry of life, where universal