Non-steroidal Pregnancy-Terminating Agents: Design, Synthesis and Structure–Activity Relationships of 2-Aryl-1,2,4-triazolo[1,5-a]pyridine

The syntheses and the pregnancy-terminating activity relationships of compounds 5a–n are reported. Compounds 5b and 5l are found to be more potent than DL-111—a known drug having effective pregnancy-terminating activity in vitro. Further research shows compounds 5b and 5l have the same activity as DL-111 in vivo. We also found an exciting result that they have excellent anti-implantation activity after oral administration.