Carboxylic acid 6 was subjected to thioester formation in the same manner as used earlier to form 3. The resulting 7, without isolation, was then treated with nitrile amine salt 8 in concentrated EtOAc (2 M) at rt to afford 9 (94% over 2 steps). This convergent approach avoids the linear route used by Pfizer involving a primary amide intermediate that then requires the Burgess reagent to effect dehydration. While column chromatography was required in our hands for isolation of pure 9 owing to practical limitations associated with small academic work, large-scale purification of this intermediate should be possible by precipitation.