The structures of mycotrienins I and II have been determined mainly by their NMR spectral analysis. Mycotrienins are unique ansamycin antibiotics containing a 21-membered macrocyclic lactam ring and a cyclohexylcarbonyl moiety. The labeling experiments with sodium [1-13C]acetate and sodium [1-13C]propionate revealed that six acetate units and two propionate units were incorporated into the molecule of mycotrienin I.
