Complex sentence: Pyrrolidinone was the first functional group to significantly increase potency, and from there it was further increased by a morpholinone group instead, then groups R2 and R3 were substituted for various groups, which were all less potent than the hydrogen, which was the final result.
Split into simpler sentences: Pyrrolidinone was the first functional group to significantly increase potency, and from there it was further increased by a morpholinone group instead. Groups R2 and R3 were then substituted for various groups, which were all less potent than the hydrogen, which was the final result.