centrifuged and then the amount of histamine and srs a in the supernatant was measured the amount of histamine was measured by a fluorometry in accordance with the method of may et al cf j allerg vol 40 page 12 1970 the amount of srs a was measured by a bioassay using an isolated guinea pig ileum that is the guinea pig ileum was suspended within magnus vessel and thereto were added an antihistaminic an antiacetylcholine agent and a test solution and based on the shrink of guinea pig ileum the amount of srs a was calculated the inhibitory rate of the compounds of this invention against release of histamine and srs a is shown in table 1 table 1______________________________________ concen tration of release inhibitory compound rate test compounds u03bcm histamine srs a______________________________________diethyl 6 piperidino 100 12 2 46 6pyrimidine 2 4 dioxa matediethyl 4 chloro 100 24 5 52 7pyrimidine 2 6 dioxa mate monohydratediethyl 6 methoxy 100 44 2 57 6pyrimidine 2 4 dioxa mate monohydratediethyl 6 morpholino 100 36 2 52 6pyrimidine 2 4 dioxa matediethyl 6 pyrrolidino 100 16 1 32 8pyrimidine 2 4 dioxa matedimethyl 6 piperidino 100 32 1 50 0pyrimidine 2 4 dioxa matedimethyl 6 morpholino 100 27 7 47 3pyrimidine 2 4 dioxa matedimethyl 6 pyrrolidino 100 19 9 40 2pyrimidine 2 4 dioxa matedimethyl 6 homopiperi 100 26 3 49 2dinopyrimidine 2 4 dioxamatediisopropyl 6 morpho 100 30 8 59 9linopyrimidine 2 4 dioxamatedi n propyl 6 piperi 100 31 6 52 3dinopyrimidine 2 4 dioxamatedi n propyl 6 morpho 100 29 8 50 0linopyrimidine 2 4 dioxamatedibenzyl 6 piperidino.