Abstract
During the past 25 years or so, there has been almost undreamed of progress in understanding the pathways by which living systems synthesize the remarkable range of substances they contain. This progress could not have been made had not isotopes of carbon, nitrogen, hydrogen and oxygen become available in quantity at a time when the intellectual climate was right for their penetrating application in biosynthetic research. It was by his generation of far-reaching ideas about biosynthesis that Sir Robert Robinson made such a major contribution to establishing this right climate. His thinking pointed the way for many studies on living systems. Several examples will be discussed which were of particular interest to Sir Robert, such as the biosynthesis of morphine and colchicine, and another topic which is currently at a fascinating stage of development, the biosynthesis of natural porphyrins. New equipment and techniques, especially 13C n.m.r. spectroscopy and high-pressure liquid chromatography, have helped in a borad study of the biochemical conversion of porphobilinogen into uroporphyrinogen-III which must be formed by some rearrangement process. It is established that a single intramolecular rearrangement occurs and that this step comes at the end of the assembly of four porphobilinogen units which forms the unrearranged bilane.
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