Process of obtaining a spirohydantoin and its salts

摘要

The spiro-hydantoin cpd. of formula (I) and its salts, for treatment and prophylaxis of cataracts, neuropatias and diabetic retinopatia, are made by (a) reaction of 6-fluoro 4-chromanone with trimethyl-silyl cyanide in CH2Cl2 in presence of ZnI2 at reflux temp.; (b) hydrolysis of the prod. with HCl in methanol and water, at 60 deg. C; (c) treatment with ammonium carbonate in methanol and water; and (d) sepn. of the D-isomer by fractional crystallisation from alcohol of the salt with L-(-)- a-methyl benzylamine, and final splitting in acid medium.