(4-nitrophenyl) (2S)-1-[(2S)-2-[[2-hydroxy-2-(phenylmethoxycarbonylamino)propanoyl]amino]-3-phenylpropanoyl]pyrrolidine-2-carboxylate                                                                                                                                                                                                                                                                                                          生成                                                 
(5-benzyl-10b-hydroxy-2-methyl-3,6-dioxo-octahydro-oxazolo[3,2-a]pyrrolo[2,1-c]pyrazin-2-yl)-carbamic acid benzyl ester