Development of a Synthetic Process towards a Hepatitis C Polymerase Inhibitor

The synthesis of 2-(4-{2-[(2R)-2-Cyclopentyl-5-(5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidin-2-ylmethyl)-4-hydroxy-6-oxo-3,6-dihydro-2H-pyran-2-yl]-ethyl}-2-fluoro-phenyl)-2-methyl-propionitrile (1) on multikilogram scale is described. Initial synthesis of this clinical candidate for inhibition of the hepatitis C viral polymerase (HCVP) protein was executed via a racemic synthetic route coupled with chiral HPLC separation. Due to the achiral route and instability of key intermediates, the initial route was determined to be unsuitable for large-scale manufacture. An alternate route was developed utilizing a convergent Heck coupling, resolution of a carboxylic acid via diastereomeric salt formation, and an efficient chemical recycling of the undesired enantiomer.