Synthesis and structure-activity relationship of 4-alkoxy-thieno[2,3-b]pyridine derivatives as potent alkaline phosphatase enhancers for osteoporosis treatment.

The synthesis and structure-activity relationships of a novel series of 3-aminothieno[2,3-b]pyridine-2-carboxamides were explored. Our efforts were focused on modifying the C-4 substituent of the thienopyridine ring to develop orally available bone anabolic agents. 4-Alkoxy derivatives were found to be novel ALPase enhancers without inhibitory effect on P450 activity. Among these derivatives, compound 6k was orally administered to ovariectomized rats, and it was found to significantly improve areal bone mineral density at a dose of 30 mg/kg/day.