Compounds of the formula ##STR1## Y is O or S, *A is paraphenylene or *--(CH.sub.2).sub.n --(X).sub.m --(CH.sub.2).sub.r --, X is O, S or --CH.dbd.CH--, n or r, independently, are integers from 0 to 3, s is an integer from 0 to 1, m is an integer from 0 to 1, provided that when m is 1, n+s must be at least 2, R.sub.1 and R.sub.2, independently, are hydrogen, lower alkyl, cycloalkyl, lower alkenyl, Het, Aryl, R.sub.3, R.sub.4 and R.sub.8, independently, are hydrogen, lower alkyl, aryl, R.sub.5 and R.sub.6, independently, are hydrogen or lower alkyl, R.sub.7 is hydrogen, lower alkyl, cycloalkyl, Het-lower alkyl or aryl, Het is a monocyclic 5- or 6-membered hetero aromatic or a bicyclic heteroaromatic radical containing one or two hetero atoms selected from nitrogen, oxygen and sulfur, which radical may be substituted by lower alkyl, halogen or aryl, and the asterisk denotes the point of attachment,and when R.sub.6 and R.sub.7 are different, their enantiomers and racemic mixtures thereof, when R.sub.1 and R.sub.2 are different, their geometric isomers, and pharmaceutically acceptable acid addition salts thereof, are described.The compounds of formula I exhibit activity as platelet activating factor (PAF) antagonists and are, therefore, useful in disease states characterized by excess platelet activating factor or for the prevention and treatment of cardiovascular diseases, pulmonary diseases, immunological disorders, inflammatory diseases, dermatological disorders, shock or transplant rejection.