合成路线1

Synthesis of the alkenyl cuprate (XVII): Enzymatic acylation of the racemic acetylenic alcohol (VII) with vinyl butyrate (VIII) by means of Chirazyme L9 gives a mixture of the ester (R)-(IX) and the alcohol (S)-(X). Reaction of this mixture with Ms-Cl and TEA yields a mixture of ester (R)-(IX) and the mesylate (S)-(XI). Treatment of this mixture with butyric acid and TEA results in the acylation of mesylate (S)-(XI) with optical inversion, providing pure ester (R)-(IX). Enzymatic hydrolysis of (R)-(IX) with Chirazyme L2 affords the enantiomerically pure alcohol (R)-(XIII). Silylation of alcohol (XIII) with TBDMS-Cl and imidazole gives the silyl ether (XIV), which is iodinated with Cp2ZrCl2 and I2 to yield the iodovinyl derivative (XV). Finally, the reaction of compound (XV) with the lithium cuprate (XVI) ­prepared by lithiation of thiophene with BuLi followed by treatment with copper (I) cyanide­ affords the alkenyl cuprate (XVII). Condensation of the alkenyl cuprate (XVII) with the tricyclic ketone (VI) in toluene provides the bicyclic ketone (XVIII), which is submitted to a Baeyer-Villiger oxidation with peracetic acid to give a mixture of the regioisomeric lactones (XIX) and (XX). The minor and unwanted regioisomer (XIX) is selectively hydrolyzed by treatment with aqueous Na2CO3 and separated by crystallization. Reduction of lactone (XX) with DIBAL in toluene gives lactol (XXI), which is submitted to a Wittig condensation with (4-carboxybutyl)triphenylphosphonium bromide and t-BuOK in THF, followed by esterification with isopropyl iodide and DBU, yielding a mixture of the monosilylated compounds (XXIII) and (XXIV) due to migration of the silyl group on the cyclopentane ring. Finally, this mixture is deprotected with HCl in isopropanol.