Asymmetric Synthesis of Usseful Natural Products by Means of Organosilicon Compounds

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We have previouly described highly diastereoselective intramolecular bissilylation of optically active 3- (1,4-pentadienyl) phenylmethyl disilanylether catalyzed by palladium (tert-alkylisocyanide) complex, producing 3 (R), 4 (R), 5 (R) -trisubstituted 2-silatetrahydrofuran in high yield. The highly controlled diastereoface selection in the intramolecular bis-silylation is remarked. The (R,R,R) -2-silatetrahydrofuran thus prepared was synthetically elaborated for total synthesis of (-) -avenaciolide as follows. Rhodium catalyzed regioselective hydroboration of the vinyl group on the five membered (R,R,R) -2-silatetrahydrofuran was followed by oxidation to give the corresponding primary alchohol. Next, the two silicon-carbon bonds were oxidatively cleaved to convert to the corresponding alchohols with retention of stereochemistry. After appropriate protection and then deprotection, the primary alcohols were oxidized to give the corresponding bis-lactone under acidic condition. Finally, selective methylenation on the lactone ring furnished (-) -Avenaciolide. The total synthesis of (-) -Avenaciolide in this research presented a new and efficient approach on the basis of stereoselective construction of silicon-carbon bonds, which are synthetic equivalents to hydroxy groups.