合成路线1

Synthesis of the tricyclic ketone intermediate (VI): Optical resolution of racemic bicyclo[3.2.0]hept-2-en-6-one (I) by reaction with SO2 and (+)-a-methylbenzylamine (II) yields a mixture of diastereomeric salts of the a-hydroxysulfonic acid with the chiral amine (II), which are separated by crystallization. Treatment of the purified salt (III) with aqueous Na2CO3 results in the pure enantiomer (­)-(I). Reaction of (­)-(I) with 1,3-dibromo-5,5-dimethylhydantoin (DBDMH) in acetone/water affords the bromohydrin (IV), which is treated with TBDMS-Cl and imidazole to provide the silyl ether (V). Finally, reaction of the protected bromohydrin (V) with potassium tert-butoxide in toluene gives the target tricyclic ketone intermediate (VI).