Process for the preparation of chiral hydantoins

Abstract

A novel process for the synthesis of chiral hydantoins of the structure ##STR1## wherein X is fluoro or chloro, from the corresponding 6-halo-4-chromanone of the structure ##STR2## is described. The compounds I are valuable in the treatment of certain chronic complications arising from diabetes mellitus. In addition the compound of the formula I wherein X is chloro possesses complementary hypoglycemic activity. The process comprises the sequence of dehydrative coupling of the halochromanone (II) with S-(-)-alpha-methylbenzylamine to form the imine of structure ##STR3## addition of hydrogen cyanide to form the nitrile of structure ##STR4## condensation with chlorosulfonylisocyanate (or its equivalent) to form the alpha-methylbenzylhydantoin of structure ##STR5## and finally solvolysis of the latter to the chiral hydantoin of structure I.

Dependencies are inferred from the claim text.