Patent ID: 8258313

Claim:
A method for producing a hydantoin ring compound which is represented by the following formula (I): wherein the numerals attached to individual ring-constituting elements represent the positions of the ring-constituting elements, wherein one diastereomer is selectively separated from a mixture of a pair of diastereomers each having a diastereo-face containing the position 1 asymmetric carbon of the formula (I) and one asymmetric carbon present in the spiro ring of 4 carbon atoms bonding to the carbon of position 1, the method comprises the following steps of: (1) reacting, in a solvent, the mixture with at least one protecting agent selected from the group consisting of di-tert-butyl dicarbonate, tert-butyloxycarbonyl fluoride, benzyloxycarbonyl chloride, tert-butyldimethylsilyl chloride and tosyl chloride, to directly or indirectly form a mixture of a pair of “diastereomers each having one protective group” having a structure represented by the following chemical formula (II): wherein the numerals attached to individual ring-constituting elements represent the positions of the ring-constituting elements; R 3 is a protective group selected from the group consisting of tert-butyloxycarbonyl group, benzyloxycarbonyl group, tert-butyldimethylsilyl group and tosyl group, comprising a pair of “diastereomers each having one protective group” each having a diastereo-face containing the position 1 asymmetric carbon of the above chemical formula (II) and one asymmetric carbon present in the spiro ring of 4 carbon atoms bonding to the carbon of position 1, (2) selectively precipitating one diastereomer of the pair of “diastereomers each having one protective group” from a solution containing the mixture of the pair of “diastereomers each having one protective group”, to obtain a solution containing the precipitated diastereomer, wherein the selective precipitation occurs during the reaction of step (1), after the reaction of step (1) or both during and after the reaction of step (1), (3) separating the precipitated diastereomer from the solution containing the precipitated diastereomer of step (2) to obtain a compound of the formula (II), and (4) contacting the compound of the formula (II), separated in step (3), with an acid to eliminate the protective group.