合成路线1

C10-C16 Fragment: The stereocontrolled reduction of ketoester (XIX) with Me4NHB(OAc)3 in acetonitrile/AcOH gives the dihydroxyester (XX), which is dehydrated to the lactone (XXI) with PPTS in refluxing benzene. The protection of (XXI) with triethylsilyl chloride as usual affords the fully silylated lactone (XXII), which is condensed with benzyloxymethyllithium in THF and reduced with BF3/Et2O and triethylsilane giving the benzyloxymethyl derivative (XXIII). The selective deprotection of (XXIII) with BF3/Et2O yields the 4-hydroxy derivative (XXIV), which is desilylated with TBAF in THF to give the diol (XXV). The silylation of (XXV) with TBDMS-OTf and lutidine in dichloromethane yields the fully protected compound (XXVI), which is debenzylated with H2 over Pd/C in acetic acid/ethyl acetate affording the carbinol (XXVII). Finally, this compound is oxidized with oxalyl chloride and triethylamine in DMSO to provide (XXVIII), the desired C10-C16 fragment.