Identification of neutral 4-O-alkyl quinolone nonpeptide GnRH receptor antagonists

A series of neutral, nonbasic quinolone GnRH antagonists were prepared via Mitsunobu alkylation of protected and unprotected 4-hydroxy quinolone intermediates. The synthetic route was improved by utilization of unique reactivity and convergency afforded by the use of mono and bis-trimethylsilylethyl protected quinolones. Potent neutral GnRH antagonists were identified, including ether and lactam derivatives, that show similar in vitro binding affinity and functional activity as compared to the earlier basic 4-aminoalkyl quinolone series of nonpeptide GnRH antagonists.