合成路线1

The regiocontrolled condensation of the silylated propargyl aldehyde (LXI) with the chiral borane (LXII) gives the secondary alcohol (LXIII), which is silylated with TBDMS-OTf and lutidine in dichloromethane to the silyl ether (LXIV). The ozonolysis of the terminal double bond of (LXIV) with O3 in dichloromethane yields the aldehyde (LXV), which is condensed with the phosphonate (LXVI) by means of NaH in THF affording the unsaturated heptanoic ester (LXVII). The reduction of the ester group of (LXVII) with DIBAL in THF gives the alcohol (LXVIII), which is epoxidized with MCPBA as usual to the epoxide (LXIX). The condensation of (LXIX) with the Grignard reagent (LXX) in THF yields the diol (LXXI), which is selectively esterified with pivaloyl chloride affording the monopivalate (LXXII). The cyclic transketalization of (LXXII) catalyzed by HF in acetonitrile/water gives the cyclic ketal (LXXII), which is finally hydrolyzed by means of K2CO3 in methanol to provide the desired intermediate, the ethynyl derivative (LIX).