(s)-isopropyl 2-(((s)-(((2r,3r,4r,5r)-5-(2,4-dioxo-3,4-dihydropyrimidin-1-(2h)-yl)-4-fluoro-3-hydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)amino)propanoate cristallin