Morphology-guided cell-based screening of the extract of a Mycale sp. marinesponge led to the isolation of two trisoxazole macrolides, miuramides A (1) and B (2), which induced characteristic morphological changes in 3Y1 cells. The structure of 1 including absoluteconfiguration was elucidated by a combination of the analysis of spectroscopic data, derivatization, and degradation. Both compounds exhibit
In the course of our screening program for regulators of a molecular chaperone GRP78 expression, we isolated a novel inhibitor of GRP78 expression, designated as prunustatin A, from Streptomyces violaceoniger 4521-SVS3. The planar structure of prunustatin A was determined to be an oxidized type of the neoantimycin family. Its absolute stereochemistry was established to be 2R, 4S, 6S, 7R, 9S, and 29S by analyzing chemically degraded components obtained from the derivative of prunustatin A.