TOTAL SYNTHESIS OF TAUTOMYCIN

A convergent stereocontrolled synthesis of the antifungal antibiotic tautomycin, a potent protein phosphatases inhibitor, has been achieved first via key aldol coupling of two large subunits, a right-hand C-1-C-21 ketone and a left-hand aldehyde (left from C-22). The C-1-C-10 segment was synthesized through a remote stereochemical control process using a spiroketal template. After joining with the C-11-C-18 segment, the spiroketal moiety was selectively constructed. Then the right-hand C-1-C-21 ketone was synthesized via Roush asymmetric crotylboration. The left-hand aldehyde was prepared from a C-21-C-26 Segment and a dialkylmaleic anhydride segment. Completely stereoselective assemblage of the two subunits, the right-hand and the left-hand, was achieved by employing the Mukaiyama aldol reaction. Further functional group manipulations including desilylation, oxidation at C-2, and deprotection of tert-butyl ester with concomitant anhydride formation provided tautomycin which was identical with the natural product. As a preliminary study, derivatizations and degradation of the natural product were also examined to support the total synthesis.