Structure of entinostat Form B, C₂₁H₂₀N₄O₃, derived using laboratory powder diffraction data and density functional techniques

The crystal structure of entinostat Form B, C₂₁H₂₀N₄O₃, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. Entinostat crystallizes in space group <i>Pna</i>2₁ and the crystal structure consists of inter-locking layers of entinostat mol-ecules parallel to the <i>bc</i> plane. A strong N-H⋯N hydrogen bond links the mol-ecules into zigzag chains propagating along the <i>b</i>-axis direction. The graph set for this pattern is <i>C</i> ¹ ₁(8). Two N-H⋯O hydrogen bonds link the mol-ecules along the <i>c</i>-axis direction. The graph sets for this pattern are <i>C</i> ¹ ₁(4) and <i>C</i> ¹ ₁(7).