CONFORMATIONAL ANALYSES OF FIVE NOVEL SMOOTH MUSCLE RELAXANT AGENTS. Qing-chuan YANG, Hong-ming LI, You-qi TANG (Department of Chemistry, Peking University, Beijing 100871, PRC) Wen-long Huang (Institute of Pharmacochemistry, China Pharmaceutical University, Nanjing 210009, PRC)

The benzopyran compounds have been extensively studied as potassium channel activator which relax smooth-muscle and lower blood pressure. Praeruptorin C isolated from chinese "Qian-Hu" herbal drug, also belonging to benzopyran compound, was demostrated to cause inhibition of the calcium-induced tension development in vascular smooth muscle and myocardial muscle, similar the effects of a calcium antagonist. According to the molecular feature of praeruptorin C, 50 analogue compounds were synthesized. the conformational analyses of the five compounds showing higher inhibition of the calcium entry into smooth muscle cells induced by high-K⁺ were carried out with single-crystal X-ray analyses.

Compound R1 R2,R3 R4 R5

1 NO₂ CH3 H :NOCOC₆H₅

2 NO₂ CH3 4-ClC₆H₄COO 4-ClC₆H₄COO

3 CN CH₃ OH OH

4 CN CH₃ H 4-(CH₃O)C₆H₄COO

5 CN cyclo(CH₂)₅ H :NOCOCH₃