BE-14348 substances, new specific estrogen-receptor binding inhibitors. Production, isolation, structure determination and biological properties.

Streptomyces graminofaciens BA14348, isolated from a soil sample, was found to produce new specific inhibitors of estrogen binding to its receptor. Five related substances, BE-14348A approximately E, were isolated, and their structures were determined by analyses of spectral properties. Of these substances, A was identical with the known flavanone, naringenin. On the other hand, B, C, D and E were all new compounds; the structure of B was determined to be 2(S): 3(S)-3-methyl-4',5,7-trihydroxyflavanone, C was a racemic mixture of 2(S): 3 (R) and 2(R): 3(S)-3-methyl-4',5,7-trihydroxyflavanone; D and E were 8-chloro derivatives of B and C, respectively.