合成路线1

The intermediate octadienal derivative (XXXI) has been obtained as follows: The selective monosilylation of 3(R),4-dihydroxybutyric acid methyl ester (XIV) by means of Tbdms-Cl and imidazole in dichloromethane gives the terminal silyl ether (XV), which is treated with PmbOC(=NH)CCl3 and TfOH in ethyl ether to yield the fully protected compound (XVI). The reduction of the ester group of (XVI) by means of LiAlH4 in THF affords the butanol derivative (XVII), which is subjected to Dess-Martin oxidation to furnish the corresponding aldehyde (XVIII). The condensation of (XVIII) with phosphonate (XIX) by means of DIEA and LiCl in acetonitrile provides the hexenoic ester (XX), which is reduced with DIBAL to the corresponding unsaturated alcohol (XXI). The reaction of (XXI) with Tbdps-Cl and imidazole gives the silyl ether (XXII), which is selectively monodesilylated by means of TsOH in ethanol to yield the alcohol (XXIII). The Swern oxidation of (XXIII) affords the corresponding aldehyde (XXIV), which is methylated with MeMgCl to provide the secondary alcohol (XXV). The Swern oxidation of (XXXV) yields the methyl ketone (XXVI), which is condensed with the intermediate 4-methyl-3,6-dihydro-2H-pyran-2(S)-carbaldehyde (XIII) by means of (cHex)2BCl and TEA, followed by a treatment with MsCl and TEA to afford the octadienone (XXVII). The reduction of (XXVII) by means of Zn(BH4)2 in ethyl ether provides the octadienol (XXVIII), which is silylated with Tbdms-OTf and lutidine to give the silyl ether (XXIX). The selective monodeprotection of (XXIX) by means of TBAF in AcOH yields the octadienol (XXX), which is oxidized with DMP to afford the intermediate octadienal derivative (XXXI)