(S)-6-fluoro-3-methyl-3,4-dihydroquinoxalin-2(1H)-one   、                                                                                      4-{[(2S)-2-ethyl-7-fluoro-3-oxo-3,4-dihydroquinoxalin-1(2H)-yl]sulfonyl}phenyl carbonate                                                                                                                                                                                                                                                                                                          以to yield ethyl 4-{[(2S)-7-fluoro-2-methyl-3-oxo-3,4-dihydroquinoxalin-1(2H)-yl]sulfonyl}phenyl carbonate的产率得到ethyl 4-{[(2S)-7-fluoro-2-methyl-3-oxo-3,4-dihydroquinoxalin-1(2H)-yl]sulfonyl}phenyl carbonate