Examples

The deduction of the biosynthesis of griseofulvin, though an early example, is typical. First was the hypothesis of the biosynthesis (Figure 5.2). This predicted which carbon atoms should be labelled if the compound was made using [l-I4C]acetate. Figure 5.3 shows the degradation that was carried out by A. J. Birch and his group. Note the proportion of radioactivity in the various parts is important, and that the degradation of acetic acid formed by strong oxidation, via acetone and then iodoform gives the labelling of the carboxylate carbon atom. Such degradation studies are very skilled and time-consuming.

Figure 5.2 The hypothesis for the biosynthesis of the antibiotic griseofulvin using sodium [ 1-!4C]acetate. The black dots in the supposed intermediate polyketide and the product indicate which carbon atoms should be labelled

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