Solid-State NMR Studies of Form I of Atorvastatin Calcium

Solid-state 13C, 19F, and 15N magic angle spinning NMR studies of Form I of atorvastatin calcium are reported, including chemical shift tensors of all resolvable carbon sites and fluorine sites. The complete 13C and 19F chemical shift assignments are given based on an extensive analysis of 13C–1H HETCOR and 13C–19F HETCOR results. The solid-state NMR data indicate that the asymmetric unit of this material contains two atorvastatin molecules. A possible structure of Form I of atorvastatin calcium (ATC-I), derived from solid-state NMR data and density functional theory calculations of various structures, is proposed for this important active pharmaceutical ingredient (API).