Purity >99%. LL-Z 1640-4 is a cis -enol resorcylic acid lactone that has been shown to exhibit both antiviral and antiprotozoan activity. While LL-Z 1640-4 is inactive against JNK/p38 kinase signaling, its companion antibiotic, (5Z)-7-oxo zeaenol , has been identified as an irreversible inhibitor of the MAPKKK, TAK1, blocking T cell activation. Thus, LL-Z 1640-4 is useful as negative control to help dissect the selectivity of this MAPKKK inhibitor.