The present invention provides a process for the production of calcium salts of hydantoic acids and which comprises the steps of reacting a hydantoin with a calcium base material such as calcium hydroxide in an aqueous medium at a sufficient temperature and for a sufficient period of time to form the calcium salt of the corresponding hydantoic acid and then separating the calcium salt of such acid from the reaction mass. This separation can include the further steps of cooling the reaction mass down to facilitate the precipitation of the acid/salt crystals and then separating the precipitate by means of filtering or centrifugating. These acids can then be subjected to a HNO.sub.2 -mediated decarbamoylation process followed by an optical resolution step to thus provide high yields of D-p-hydroxyphenylglycine which is a key synthetic immediate or building block for semi-synthetic penicillin and cephalosporins.