3-t-butoxycarbonylamino-2-(4-thioureidophenyl)propionic acid methyl ester   、                                                                                      
碘乙烷                                                                                                                                                                                                                                                                                                          以the same procedure of Example 29 gave 0.55 g of the titled compound (yield, 96%)的产率得到3-t-butoxycarbonylamino-2-(4-(S-ethylisothioureido)phenyl)propionic acid methyl ester