合成路线1

The ozonolysis of cylcoheptene (I) with O3 in dichloromethane, followed by a treatment with methanol and p-toluenesulfonic acid gives 7,7-dimethoxyheptanal (II), which is condensed with methoxycarbonyl-methylenetriphenylphosphorane (III) in methanol yielding methyl 9,9-dimethoxy-2-nonenoate (IV). The condensation of (IV) with 2(S)-(tetrahydropyranyloxy)propanal (V) by means of LDA in THF/HMPA affords the beta-hydroxyester (VI), which is cyclized by means of p-toluenesulfonic acid and mesyl chloride affording the furanone (VII). The hydrolysis of the acetal group of (VII) with Amberlyst 15 gives the aldehyde (VIII), which is condensed with the phosphorane (IX) yielding the unsaturated thioester (X). The cyclization of (XV) by means of Et2AlCl in toluene affords the tricyclic thioester (XI), which is reduced with RaNi in ethanol/ethyl ether affording the carbinol (XII). The reaction of (XII) with tosyl chloride and thiophenol provides the pheylsulfanyl derivative (XIII), which is reduced at the lactone group with iBu2AlH in ethyl ether giving the lactol (XIV). The methylation of the lactol (XIV) with BF3/Et2O and methanol yields the cyclic ketal (XV), which is finally oxidized with meta-chloroperbenzoic acid (MCPBA) in dichloromethane to afford the desired tricyclic sulfone intermediate (XVI).