2-Oxa-5,8-diazabicyclo[10.3.1]hexadecane, cyclic peptide deriv.; 3-Chloro-erythro-β,5-dihydroxy-N-methyl-L-tyrosyl-3,4-didehydro-L-valyl-3-hydroxy-L-isoleucyl-3,4-didehydro-L-prolyl-(E)-2,3-didehydroisoleucyl-(E)-2,3-didehydroaspartic acid cyclic (15→3)-ether; NSC 381839

Phomopsin A is an acidic 13-membered cyclic hexapeptide-like metabolite with three unusual amino acids linked in an "ansa" macrocycle with a three amino acid "tail", terminating in a dicarboxylic acid. Phomopsin A is a potent mycotoxin produced by the fungus Phomopsis leptostromiformis and is the causative agent of lupinosis in livestock fed infected lupins. Phomopsin A is an important bioprobe for understanding cellular structural proteins. It acts by selectively binding to dimeric tubulin, inhibiting the formation of the microtubule spindle to block cell division. Phomopsin A binds to tubulin at a site overlapping that of vinblastine and maytansine. Uniquely, phomopsin A protects tubulin from decay.