A large-scale, chromatography-free synthesis of a potent and selective Cathepsin K inhibitor 1 is reported. The key asymmetric center was installed by addition of (R)-pantolactone to the in situ-generated ketene 4a. The final step of the convergent synthesis of 1 was completed via Suzuki coupling of aryl bromide 7a with unprotected aryl piperazine boronic acid 13. Residual palladium and iron generated in the Suzuki coupling were efficiently removed from crude 1 via a simple extractive workup using lactic acid.

Two synthetic strategies to the COX-2 specific inhibitor 1 have been described that allowed its preparation in large quantities in 79% overall yield from (S)-2-hydroxy-2-methylbutyric acid. These studies have led to the identification of an efficient resolution of (±)-2-hydroxy-2-methylbutyric acid and a novel thionyl chloride aided formation of amide 11 from acid 6.

The asymmetric dihydroxylation of 1-aryl-1′-pyridyl alkenes afforded the diols in high yield and excellent enantioselectivity.

Selective monolithiation of 2,5-dibromopyridine at either the 2-position or the 5-position is reported. Solvent and concentration strongly influence the selectivity. Coordinating solvents and higher concentration favor the 5-position while non-coordinating solvents and lower concentration favor the 2-position. (C) 2000 Published by Elsevier Science Ltd.