First total synthesis of Debilisone C.

Total synthesis of Debilisone C, a lactone containing conjugated endiyne has been achieved. The adopted strategy involves the stereoselective construction of the five membered lactone ring and the C20 endiyne chain followed by regioselective coupling of both the parts. The lactone was obtained from the oxidative cleavage of the hydroxy olefin which was derived from the benzyl protected S-epichlorohydrine by regioselective epoxide opening with allyl trimethyl silane in presence of a Lewis acid at -78 °C. Takai olefination, Pd(0)/Ag(1) catalyzed cross-coupling reaction and selective substitution of trimethylsilyl groups were successfully utilized to establish the C20 polyyne chain. The final coupling of both the parts have been carried out by alkyl coupling using LDA in THF-DMPU (1 : 1).