合成路线1

The reaction of carbaldehyde (VII) with phenylsulfanylacetylene (XVII) by means of LiHMDS in toluene gives the intermediate lithium alcoxide (XVIII), which is condensed with benzoyl chloride (XIX) to yield the ester (XX). The migration of the aroyl group of (XX) to the methyl ketone group under basic medium (LiHMDS) affords diketone (XXI), which is oxidized with DMP, complexed with Co2(CO)8 and debenzylated, providing the cobalt complex (XXII). The cycloaddition of (XXII) by means of Me2SiCl2, chloranil in refluxing toluene, followed by protection of the peri-OH groups with tBu2Si(OTf)2 and oxidation of the sulfanyl group with MCPBA, gives the polycyclic spiro compound (XXIII). The reaction of (XXIII) with chloroacetate (XXIV) by means of Ts-OH yields the chloroacetoxy compound (XXV). Selective demethylation of (XXV) with trimethylsilyl iodide affords the pyridinone (XXVI), which is oxidized with SeO2 in dioxane to provide the carbaldehyde (XXVII). The condensation of (XXVII) with phosphonium bromide (XXVIII) by means of BuLi in THF furnishes the alkylated precursor (XXIX), which is finally deprotected by means of BBr3 in dichloromethane and oxidized by air to afford the target compound.