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Novel O-acylated (E)-3-aryl-6,7-dihydrobenzisoxazol-4(5H)-one oximes were designed as potential HSP90 inhibitors. A series of the compounds was synthesized by oximation of (E)-3-aryl-6,7-dihydrobenzisoxazol-4(5H)-ones followed by O-acylation with acylamidobenzoic acids. The obtained compounds showed an antiproliferative effect on three breast cancer cell lines (MCF7, MDA-MB-231 and HCC1954). Compound 16s exhibited high antiproliferative potency against HCC1954 breast cancer cells with the IC 50 value of 6 µM was selected for in-depth evaluation. Compound 16s did not inhibit the growth of normal epithelial cells. We have demonstrated that the compound 16s can induce apoptosis in cancer cells via inhibition of HSP90 "client" proteins including a key oncogenic receptor, HER2/neu. Described here compounds can be considered for further basic and preclinical investigation as a part of HSP90/HER2-targeted therapies., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

An effective method for the synthesis of 8-aryl-4,5-dihydrothiazolo[4',5':3,4]benzo[1,2- c ]isoxazol-2-amines was developed. This method includes the α-keto bromination of 3-aryl-6,7-dihydrobenzo[ c ]isoxazol-4(5 H )-ones followed by the condensation of the obtained bromo derivatives with thiourea in acetonitrile. Using virtual screening, a series of acylated derivatives of the obtained compounds were selected as potential HSP90 inhibitors. These compounds were prepared and evaluated as antiproliferative agents against three cancer cell lines (A431, 22Rv1, and MCF-7). Compounds 8b, 8c and 8q exhibiting high antiproliferative potency against MCF-7 breast cancer cells with IC 50 values ranging from 2.3 to 9.5 μM were chosen for in-depth evaluation. The selected compounds had remarkable effects on HSP90 client proteins, including steroid hormone receptors and the anti-apoptotic factor BCL2. The obtained compounds are of interest for anticancer drug development.