合成路线1

Aldehyde (XXI): The condensation of oxazolidinone (XXXVII) with aldehyde (XXXVIII) by means of dibutylboron trifluoromethanesulfonate in dichloromethane gives compound (XXXIX), which is reduced with LiBH4, tosyl chloride and lithium triethylborohydride as before, yielding the alcohol (XL). The deprotection of (XL) with tetrabutylammonium fluoride in THF followed by formation of a dioxane ring with p-methoxybenzaldehyde diethyl acetal and CSA in dichloromethane affords compound (XLI), which is submitted to a reductive ring opening with diiosbutylaluminum hydride in dichloromethane, followed by an oxidation with oxalyl chloride in DMSO/dichloromethane, yielding the aldehyde (XLII). The condensation of (XLII) with the unsaturated iodo compound (XLIII) by means of CrCl2 in DMSO gives the hydroxy derivative (XLIV), which is finally silylated with triisopropylsilyl trifluoromethanesulfonate in dichloromethane, selectively desilylated with HF - pyridine and oxidized with oxalyl chloride in DMSO/dichloromethane to the intermediate aldehyde (XXI) (see K.C. Nicolau et al., J Chem Soc Chem Commun 1993, 7: 619). The intermediate (XLIII) is prepared by ozonolysis of the protected unsaturated diol (XLV), followed by reaction with dimethylsulfide and tetrabromomethane - triphenylphosphine to obtain an acetylenic intermediate, which is methylated with butyllithium and methyl iodide to the acetylene (XLVI). Finally, this compound is iodinated with iodine and (cyclopentadienyl)2ZrHCl in dichloromethane to the intermediate (XLIII) (see K.C. Nicolau et al., J Chem Soc Chem Commun 1993, 7: 619). (1,2)