New approaches to the synthesis of Cycloproparadicicol and its analogs as preclinical anticancer agents based on Hsp90 inhibition

ORGN 681

Xiaoguang Lei, Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, Mail Code 3135, New York, NY 10027 and Samuel J. Danishefsky, s-danishefsky@ski.mskcc.org, Laboratory for Bioorganic Chemistry, Sloan-Kettering Institute for Cancer Research, 1275 York Ave. (Box 106), New York, N.Y. 10021 and, Department of Chemistry, Columbia University, Havemeyer Hall, 3000 Broadway, New York, NY 10027.
Cycloproparadicicol, a congener of natural product radicicol, is one of the most promising preclinical anticancer agents targeting Hsp90. The heat shock protein 90 (Hsp90) is an important molecular chaperone required to stabilize and refold client proteins such as Raf1 and Her2. Recently, Hsp90 has been regarded as a novel and attractive target for cancer therapies. Selective inhibition of Hsp90 could potentially facilitate the degradation of various oncogenic proteins. Cycloproparadicicol, a potent Hsp90 inhibitor (IC50 = 160 nM), showed significant inhibitory activity against MCF-7 breast cancer cells (IC50 = 49 nM) in vitro. In a preliminary in vivo study against mice implanted with human colon carcinoma (HCT-116), cycloproparadicicol (75 mg/kg, QDx7) also suppressed 68% of tumor cell growth. Unfortunately, our current synthesis of cycloproparadicicol suffers from several non-scalable and low-yielding steps that hinder its availability for further clinical studies. Furthermore, the current synthetic route is not optimal for the efficient synthesis of new analogs. Herein, a novel approach for the highly convergent and scalable total synthesis of cycloproparadicicol and novel analogs through diverted total synthesis (DTS) as well as biological evaluations of these molecules will be presented.