Absolute structure of prunustatin A, a novel GRP78 molecular chaperone down-regulator.

  title={Absolute structure of prunustatin A, a novel GRP78 molecular chaperone down-regulator.},
  author={Yukiko Umeda and Kazuo Furihata and Sho-hei Sakuda and Hiromichi Nagasawa and Ken Ishigami and Hidenori Watanabe and Miho Izumikawa and Motoki Takagi and Takayuki Doi and Yoichi Nakao and Kazuo Shin‐ya},
  journal={Organic letters},
  volume={9 21},
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. 
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A total synthesis of prunustatin A, a GRP78 molecular chaperone down-regulator, has been achieved. The key step in the synthesis is an intramolecular transesterification of the β-keto ester alcohol
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Coupling of the (+)-prunustatin A macrolide amine with benzoic acid furnished a JBIR-04 diastereoisomer whose NMR spectra did not match those of JBIr-04, thus confirming that it has different stereochemistry than (+-prunusatin A.