合成路线1

The ketalization of cis-bicyclo[3.3.0]octane-3,7-dione (I) with ethylene glycol (A) and p-toluenesulfonic acid gives the diethyleneketal (II), which by controlled hydrolysis with acetic acid-THF-water is converted into the monoketal (III). Carboxylation of (III) with diethyl carbonate by means of NaH yields the ketoester (IV), which is reduced with sodium borohydride in ethanol to afford the hydroxyester (V). Protection of (V) with dimethyl-tert-butylsilyl chloride gives the silylether (VI), which is reduced with diisobutylaluminum hydride to the alcohol (VII). Oxidation of (VII) with pyridinium chlorochromate affords the aIdehyde (VIII), which by a Wittig reaction with the sodium salt of dimethyl 2-oxoheptylphosphonate (IX) is converted into the enone (X). The reduction of (X) with zinc borohydride yields the protected alcohol (XI), which is deprotected to the corresponding dihydroxyketone (XII) by treatment with acetic acid-THF-water. Finally, this compound is submitted to a Wittig reaction with the sodium salt of 4-carboxybutyltriphenylphosphorane (XIII) in DMS.