An FKBP51 inhibitor (Ki = 6 nM); highly selective for FKBP51 over FKBP52 (Ki = >50,000 nM); decreases plasma corticosterone levels to a greater extent than control mice following dexamethasone administration (20 mg/kg); does not increase plasma corticosterone levels as high as in control mice following administration of CRF (20 mg/kg); has antidepressant-like and anxiolytic-like activity in mice (20 mg/kg)