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A new topoisomerase inhibitor, BE-10988, was isolated from the culture broth of a strain of actinomycetes. The producing strain had a close resemblance to Streptomyces fimicarius and Streptomyces xanthocidicus. The active principle was extracted from the whole broth of strain BA1 0988 with ethyl acetate and purified by silica gel chromatography and by HPLC. BE-10988 increased DNA-topoisomerasecomplex formation and inhibited the growth of both doxorubicin-resistant and vincristine-resistant P388murine leukemia cell lines, as well as sensitive P388 cell lines.

This paper describes a new type of reaction, [1,5]-sigmatropic hydrogen migration, of benzocyclobutenes, and also reports a direction of ring opening of benzocyclobutenes and a geometry of o-quinodimethanes.Benzocyclobutenes (l)1 are one kind of charming and effective intermediates for a construction of the natural prod-

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~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(7?) : 3(S)-3-methyl-4',5,7-trihydroxyrlavanone; D and E were 8-chloro derivatives of B and C, respectively.

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