Isolation and structure of an antimitotic cyclic peptide, ustiloxin F: chemical interrelation with a homologous peptide, ustiloxin B.

Ustiloxin F, a microtubule inhibitor, was isolated as a minor metabolite of Ustilaginoidea virens. The structure was determined from the spectral data and by chemical interrelation to ustiloxin B through reductive removal of the sulfoxide-containing side chain of ustiloxin B to give ustiloxin F. Ustiloxin F inhibited microtubule assembly with an IC50 value of 10.3 microM.