Antiandrogenic natural Diels--Alder-type adducts from Brosimum rubescens.

The isolation and structure elucidation of five novel natural Diels--Alder-type adducts, named palodesangrens A-E (1-5), from the Peruvian folk medicine known as "palo de sangre" (Brosimum rubescens) is described. The structures of the Diels--Alder adducts, consisting of chalcone derivatives and a prenylcoumarin, were elucidated by analysis of spectroscopic data including 2D NMR. Some of these compounds showed potent inhibitory activity towards 5 alpha-dihydrotestosterone (DHT) binding with an androgen receptor to form a DHT-receptor complex that causes androgen-dependent diseases.