5-(6-ethoxycarbonylhexyl)-1-(5-phenylpentyl)hydantoin   、                                                                                      
sodium hydroxide                                                                                                                                                              在
                                                                                                                                                                                 silica gel                                                                                                                                  作用下,
                                                                                                                                                                                                                            以to give 5-(6-carboxyhexyl)-1-(5-phenylpentyl)hydantoin crystallising from ethyl acetate-light petroleum (b.p. 60°-80° C.) in colourless prismatic needles, m.p. 90°-92° C.的产率得到5-(6-carboxyhexyl)-1-(5-phenylpentyl)-hydantoin