Abstract
Thielocin B1 (1), isolated from the fermentation broth of Thielavia terricola RF-143 in 1995, consists of five multi-substituted benzene rings, which are connected with a 2,2', 6,6'-biaryl ether and four ester linkages. Recently, it was found that 1 strongly inhibits protein-protein interactions (PPIs) of PAC3 homodimer (IC_<50>= 0.02 μM) without inhibition of other PPIs such as PAC1/PAC2 or TCF/P-catenin. Since we are interested in the mode of action mechanisms of 1, we performed total synthesis of 1, and docking studies by NMR and in silico analyses. The key intermediate 2,2', 6,6'-biaryl ether 4 was synthesized from 7-membered lactone 6, which was prepared by oxidative lactonization of benzophenone 7, followed by chemoselective reduction of the lactone and removal of the resulting alcohol. The side wing 5 was synthesized from aldehyde 8 via formation of 3 and its coupling by esterification. Condensation of biaryl ether 4 and 5 was smoothly performed using trifluoroacetic anhydride to afford 21 in high yield. Formylation of 21 by treatment with dichloromethyl methyl ether and AgOTf, followed by Kraus oxidation provided acid 2. Coupling of the resulting acid 2 with phenol 3 afforded 22 in 70% yield. Finally, removal of the benzyl groups by-hydrogenation furnished thielocin B1 (1), whose spectral data were in good agreement with those of the natural product.
