Active compounds

#The present invention relates to novel pyranopyridines having pharmacological activity, to a process and intermediates for preparing them, to pharmaceutical compositions containing them, and to their use in the treatment of mammals.

#European Patent Publications 76075, 91748, 93535, 95316, 107423, 120426, 120427, 126311 and 126367 disclose classes of compounds that are described as having blood pressure lowering activity or anti-hypertensive activity.

#A structurally distinct class of compounds has now been discovered which are pyranopyridines substituted in the 4-position by a cyclic or acyclic amide, the nitrogen atom of the amide moiety being bonded directly to the carbon atom in the 4-position. Such pyranopyridines have been found to have blood pressure lowering activity, useful in the treatment of hypertension. In addition, these compounds are believed to be K.sup.+ channel activators which indicates that they are of potential use in the treatment of disorders associated with smooth muscle contraction of the gastro-intestinal tract, respiratory system, uterus or urinary tract. Such disorders include peptic ulcers, irritable bowel syndrome and diverticular disease, reversible airways obstruction and asthma; premature labour; and incontinence. They are also indicated as of potential use in the treatment of cardiovascular disorders other than hypertension, such as congestive heart failure, angina, peripheral vascular disease and cerebral vascular disease.

#Examples of compounds of formula (I) include the compounds prepared in the Examples hereinafter.

#The present invention also provides a process for the preparation of a compound of formula (I) or a pharmaceutically acceptable salt thereof, which comprises;

#(i) acylating a compound of formula (II): ##STR3## wherein, R.sub.1 and R.sub.2 are as hereinbefore defined, R.sub.3.sup.1 is hydroxy, C.sub.1-6 alkoxy or C.sub.1-7 acyloxy, R.sub.4.sup.1 is hydrogen and R.sub.6.sup.1 is hydrogen or C.sub.1-6 alkyl, the R.sub.6.sup.1 NH group being trans to the R.sub.3.sup.1 group,