A proposed crystal structure of lifitegrast sesquihydrate Form A, (C29H24Cl2N2O7S)2(H2O)3

A proposed crystal structure of lifitegrast Form A has been derived using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Lifitegrast sesquihydrate Form A crystallizes in space group P2(1) (#4) with a = 18.2526(4), b = 5.15219(6), c = 30.1962(6) & Aring;, beta = 90.8670(19), V = 2839.35(7) & Aring;(3), and Z = 4 at 295 K. The crystal structure consists of discrete lifitegrast molecules linked by hydrogen bonds among carboxylic acid groups, carbonyl groups, and water molecules into a three-dimensional framework. The water molecules occur in clusters. Each water molecule acts as a donor in two O-H & ctdot;O hydrogen bonds, and as an acceptor. One water molecule acts as an acceptor in a water-water O-H & ctdot;O hydrogen bond, and all three water molecules are acceptors in C-H & ctdot;O hydrogen bonds. Each carboxylic acid group acts as a donor in a strong discrete O-H & ctdot;O hydrogen bond; one to a water molecule and the other to a carbonyl group. The amino groups both form N-H & ctdot;O hydrogen bonds to carbonyl groups. The powder pattern has been submitted to ICDD (R) for inclusion in the Powder Diffraction File (TM) (PDF (R)).