合成路线1

The mixed carbonate ester intermediate (X) has been obtained as follows: The reaction of dihydrofuran (I) with propargyl alcohol (II) and N-iodosuccinimide (NIS) gives the propargyl ether (III), which is cyclized by means of tributyltin hydride and AIBN in refluxing toluene to yield the perhydrofuro[2,3-b]furan (IV). The oxidation of the methylene group of (IV) with ozone in methanol/dichloromethane affords the bicyclic ketone (V), which is reduced with NaBH4 in ethanol to provide racemic (VI). The digestion of (rac)-(VI) with immobilized lipase 30 and acetic anhydride in DME provides a mixture of the (3R)-alcohol (VII) and the (3S)-acetoxy derivative (VIII) that is separated by chromatography. Finally, the (3R)-(VII) alcohol is condensed with disuccinimidyl carbonate (IX) and TEA in acetonitrile to give the target mixed carbonate ester intermediate (X).