合成路线1

The intermediate, the furanone derivative (VIII) has been obtained as follows: The reaction of propargyl alcohol (XIII) with dihydropyran and Ts-OH gives the tetrahydropyranyl ether (XIV), which is treated with ethylmagnesium bromide to yield the corresponding magnesium derivative (XV). The reaction of (XV) with propionaldehyde (XVI) in THF affords the secondary alcohol (XVII), which is benzoylated with benzoyl chloride and triethylamine affording the benzoate (XVIII). The deprotection of (XVIII) with Ts-OH gives the primary alcohol (XIX), which is oxidized with pyridinium chlorochromate (PCC) to the corresponding aldehyde (XX). The Diels-Alder reaction of (XX) with 5-ethoxy-4-methyloxazole (XXI) in refluxing toluene yields 4-(1-benzoyloxypropyl)-2-ethoxyfuran-3-carbaldehyde (XXII), which is reduced with NaBH4 in methanol to the carbinol (XXIII). The controlled oxidation of (XXIII) with MnO2/HCl affords 4-(1-benzoyloxypropyl)-5-hydroxy-3-(hydroxymethyl)furan-2(5H)-one (XXIV), which is finally treated with SOCl2 and DMF in chloroform to afford the target intermediate (VIII).