Bilaid C (YvVf-OH) is a hydroxylated analogue of a family of tetrapeptides with an unusual alternating LDLD chirality isolated from an Australian estuarine isolate of Penicillium sp. MST-MF667. Bilaid C is an isomer of bilaid A with terminal L-phenylalanine and D-tyrosines inverted to their D and L-isomers. Bilaid C exhibited very weak μ-​opioid agonist and the class formed the foundation for the design of more potent analogues, bilorphin and bilactorphin. The bioassay profile of bilaid C has not been extensively investigated.