合成路线1

A synthesis of the R-(+) isomer has also been reported: Reaction of phenethyl alcohol (I) and ethyl 3,3-diethoxypropionate (VI) in the presence of titanium tetrachloride affords the isochromane (VII), which is hydrolyzed to acid (VIII) with NaOH in aqueous ethanol. Resolution of the racemic acid (VIII) is effected by conversion into the diastereomeric salt with R-(+)-a-methylbenzylamine (IX) which, after recrystallization from dichloromethane and ethyl acetate, is liberated by treatment with hydrochloric acid, to yield the R-(-) acid (X). This acid is reduced to alcohol (XI) with borane-dimethyl sulfide in tetrahydrofuran. Treatment of XI with methanesulfonyl chloride, diisopropylethylamine, and a trace of dimethylaminopyridine (DMAP) in tetrahydrofuran affords mesylate (XII), which is subsequently treated with piperazine (V) in ethylene glycol to afford the R-(+) compound, isolated as the methanesulfonate salt.