Structural Study of Pinacidil, a Potassium‐Channel Opener Belonging to the chemical class of N‐alkyl‐N″‐cyano‐N′‐pyridylguanidines

The crystal structure of the potassium‐channel opener (R,S)‐pinacidil (2) was determined by X‐ray crystallography. Its N′, N″‐disubstitued N‐cyanoguanidine fragment was found to exhibit an unusual (Z,Z)‐conformation. X‐Ray and NMR data obtained with 2 are consistent with the predominance of the 4‐aminopyridine species over an iminopyridine tautomer in the solid state and in solution. These new structural informations may help further comparative studies of 2 and other potassium‐channel openers in elucidating structure‐activity relationships.