INCORPORATION OF ACETATE, PROPIONATE, AND METHIONINE INTO RAPAMYCIN BY STREPTOMYCES-HYGROSCOPICUS

Labelling experiments with C-13-labelled precursors demonstrated that the majority of the macrolide ring of rapamycin [1] is formed from six acetate and seven propionate units. A two-carbon unit in the ring was not labelled by acetate, propionate, glycine, or methionine. Methionine and glycine did, however, label the three methoxy groups of rapamycin to a high degree. Results from the incorporation experiments demonstrated that there were errors in the published C-13-nmr spectral assignments for rapamycin; these have now been corrected.