Synthesis and structural elucidation of a novel polymorph of alcaftadine

• Alcaftadine is characterized in solution as well as in the solid state.
• The structural ambiguity of CH2 protons is solved using 2D NMR spectra.
• The SCXRD and Hirshfeld surface helped to understand intermolecular interactions.
• PXRD and DSC data is in agreement with novel polymorph.

In this study, we have synthesized and elucidated the structure of the H1 histamine antagonist, 2-(1-methylpiperidin-4-ylidene)-4,7-diazatricyclo[8.4.0.0(3,7)]tetradeca-1(14),3,5,10,12-pentaene-6-carbaldehyde in the solution and solid-state. We have also studied the thermal dilapidation of the compound. Solution structure analysis was achieved by employing NMR spectroscopy including 2D experiments NOESY, HSQC and HMBC, while solid state investigations were undertaken using SXRD, PXRD, TGA, DSC, and IR spectroscopy. For the first time the single crystal structure of alcaftadine has now been solved. Crystallographic data are as follows: monoclinic, Cc, a = 11.5694(6) Å, b = 14.5864(6) Å, c = 10.2688(4) Å, α = 90°, β = 111.793(3)°, γ = 90°, V = 1609.07(13) Å3, Z = 4. The Hirshfeld surface analyses also have been performed using the crystal structure.

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