Abstract: The present invention relates to hitherto unknown compounds of formula or their tautomeric forms, the attachment to the pyridine ring being in the 3- or 4-position, in which R', R" are the same or different and stand for hydrogen, halogen, or trifluoromethyl, hydroxy, C.sub.1 -C.sub.4 alkyl or alkoxy, nitro, or cyano groups. Alkylene stands for a straight or branched C.sub.1 -C.sub.8 carbon chain, which may be substituted by hydroxy or halogen, nitro or cyano groups. X stands for oxygen, for --S(O).sub.n -- where n stands for an integer from 0 to 2, or for ##STR1## where R.sub.1 is hydrogen or C.sub.1 -C.sub.4 alkyl. R stands for hydrogen or for one or more C.sub.1 -C.sub.4 alkyl or alkoxy, hydroxy, halogen, trifluoromethyl, cyano, carboxamido, sulfamoyl or nitro radicals. The present compounds are of value in the human and veterinary practice for treating asthma, allergy, CNS disorders, or cancer.

Abstract: The present invention relates to hitherto unknown compounds of formula or their tautomeric forms, the attachment to the pyridine ring being in the 3- or 4-position, in which R', R" are the same or different and stand for hydrogen, halogen, or trifluoromethyl, hydroxy, C.sub.1 -C.sub.4 alkyl or alkoxy, nitro, or cyano groups. Alkylene stands for a straight or branched C.sub.1 -C.sub.8 carbon chain, which may be substituted by hydroxy or halogen, nitro or cyano groups. X stands for oxygen, for --S(O).sub.n -- where n stands for an integer from 0 to 2, or for .dbd.N--R.sub.1 where R.sub.1 is hydrogen or C.sub.1 -C.sub.4 alkyl. R stands for hydrogen or for one or more C.sub.1 -C.sub.4 alkyl or alkoxy, hydroxy, halogen, trifluoromethyl, cyano, carboxamido, sulfamoyl or nitro radicals. The present compounds are of value in the human and veterinary practice as selective serotonin receptor antagonists.