Asymmetric synthesis of an amine-azaspiro as the key intermediate of sitafloxacin

As an important intermediate of quinolone antibacterial agents such as sitafloxacin and olamufloxacin, 7-(S)-tert-butoxycarbonylamino-5-azaspiro［2. 4］heptane has received much attention. Previous syntheses suffered from low yielding and poor stereoselectivity. In this study, an asymmetric synthetic approach was developed to optically pure amine-azaspiro compound with convenient manipulation, excellent yields and high stereoselectivity.