合成路线1

Fragment coupling: Coupling of the C10-C16 fragment (XXVIII) with the C17-C27 fragment (XLIII) by means of BuLi, Ac2O and Mg in THF gives (XLVII), which is selectively deprotected with TBAF yielding the carbinol (XLVIII). The reaction of (XLVIII) with triflic anhydride and lutidine in CH2Cl2 affords the triflate (IL), which is coupled with the C1-C9 fragment (XVIII) by means of n-BuLi in THF giving the tricyclic intermediate (L). The opening of the lactol ring of (L) with triethylsilyl chloride and imidazole yields the silylated hydroxyketone (LI), which is treated first with tert-butoxycarbonyl anhydride and then with the lithium salt of benzyl alcohol in order to convert the phenylcarboxamide of (LI) into the benzyl ester (LII). The epoxidation of the dihydropyran double bond of (LII) with MCPBA followed by epoxide opening with MeOH and oxidation of the resulting alcohol with DMP in CH2Cl2 gives the oxoketal (LIII).