6-Amino-1-(4-chloro-phenyl)-3,3-diethyl-1H-pyrido[2,3-b][1,4]oxazin-2-one trifluoroacetate salt 、 、
N-叔丁氧羰基-L-丙氨酸 以to give {(S)-1-[1-(4-chloro-phenyl)-3,3-diethyl-2-oxo-2,3-dihydro-1H-pyrido[2,3-b][1,4]oxazin-6-ylcarbamoyl]-ethyl}-carbamic acid tert-butyl ester (177 mg) as a colourless gum的产率得到{(S)-1-[1-(4-chloro-phenyl)-3,3-diethyl-2-oxo-2,3-dihydro-1H-pyrido[2,3-b][1,4]oxazin-6-ylcarbamoyl]-ethyl}-carbamic acid tert-butyl ester