Anti-infectives A∥ rights re served Discovery history CH3 NHCH(CH2)3N(C2H5)2 CO,H Structural modification H3C C2h4 chloroquine nalidixic acid malarial O CO,H CO,H HN N C2H norfloxacin pipemidIc acid generation 2 generation 3 MP士海医药工业研究院 NDUSTRYAnti-infectives All rights re served Discovery history N NHCH(CH2 )3N(C2H5 )2 CH3 Cl Structural modification N N C2H5 CO2H O H3C chloroquine antimalarial nalidixic acid N N N O CO2H C2H5 HN N N O CO2H C2H5 HN N F generation 1 pipemidic acid generation 2 norfloxacin generation 3