Semotiadil  (Synonyms: SD-3211)

Semotiadil is a novel calcium antagonist whose stereochemical structure was investigated by X-ray crystallography and circular dichroism spectroscopy. X-ray structural analysis was performed using its enantiomeric salts with (S)-(+)-mandelic acid (2); 1 (mandelate salt). The R absolute configuration of 1, which was previously determined by chemical transformation of an optically active synthetic precursor, was directly confirmed by this analysis. Hydrogen bonding, charge repulsion, and hydrophobic interactions that stabilize the crystal structure were observed in the crystals. Circular dichroism spectra of 1 (mandelate salt) and 1 (hydrofuranate salt) in ethanolic solution showed similar spectral patterns. The CD bands of each chromophore were unambiguously assigned, and the conformation of the benzothiazole ring was determined using the optical rotation rule. The X-ray and CD data confirmed the P conformation of the benzothiazole ring and the equatorial position of the 2-phenyl ring in both the crystal and ethanolic solution states. These findings are in good agreement with our previous results on the conformational analysis of 2-arylbenzothiazole derivatives.

536.64

C₂₉H₃₂N₂O₆S

116476-13-2

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• [1]. Conformational Studies of Semotiadil (SD-3211), a Novel Ca2+ Antagonist