X-Ray and theoretical structural study of novel 5,6,7,8-tetrahydrobenzo-4H-pyrans

The X-ray crystal structure of three substituted tetrahydrobenzo-4H-pyrans (6a-c) is presented and the experimental findings compared with the theoretical values calculated at the semiempirical (AM1, PM3) and ab initio (HF/6-31G*) levels. A good agreement between both experimental and theoretical data is found showing a flattened boat conformation for the 4H-pyran ring and a pseudo-axial orientation of the aryl ring on the C4 position. The geometrical features of these systems (6a-c) reveal that they present the structural requirements to act as calcium antagonists. (C) 2002 Published by Elsevier Science Ltd.