An Hsp90 inhibitor (IC50s = 0.6, 0.8, and 8.5 nM for Hsp90α, Hsp90β, and GRP94, respectively); dissociates the Hsp90-p23 complex, depleting the client protein c-Met and inducing Hsp70 in c-Met amplified GTL-16 gastric tumor cells; inhibits proliferation of various human tumor cell lines in vitro and in a GTL-16 xenograft model.