Pyrrolo [2,3-d]pyrimidines have been obtained by spontaneous cyclisation of 4-aminopyrimidyl-acetaldehydes and -acetones, which in turn were prepared by hydrolysis of their acetals, and, in the case of the aldehydes, by oxidation of 4-amino-5-( 2,3-dihydroxypropyl)pyrimidines. The compounds prepared include analogues of biologically important purines.

in the number of reactive sites or the dissociation of a urease-inhibitor complex with the inhibitor assumed to be of natural origin. With the recognition that potassium ion can function as an inhibitor and phosphate ion as an activator of urease it appears that neither of the above explanations are correct and that the dilution effect is simply the consequence of a change in the relative concentrations of enzyme, activator and inhibitor.18s19 ExperimentalReagents.-The stock 0.1, 0.2, 0.3, 0.4 and 0.5 $1 buffer solutions were prepared from reagent grade dipotassium hydrogen phosphate and potassium dihydrogen phosphate and from the corresponding sodium salts. In every case irrespective of the concentration of the buffer, the $H of the solution after final dilution was 7.0 =t 0.02 a t 25'. A 1.0 M stock solution was prepared daily from urea which had been recrystallized from ethanol. The crystalline urease was prepared from Arlington jackbean meal by the method of DouncelBO all operations subsequent to the initial extraction being conducted at 5'. The thrice recrystallized urease obtained from 400 g. of meal was dissolved in 5 ml. of water 1% saturated with hydrogen sulfide at 0' and this stock solution stored a t 5'. The water used for the dilution of the enzyme stock solution was also 1% saturated with hydrogen sulfide a t 0'. The water used for all solutions was redistilled from an all-glass apparatus.Procedure.-In general the procedure used w a 5 a modification of that described by Van Slyke and Cullen9 in which the aeration step was eliminated and the ammonia determined by the method of Conway.*l In practice 2.0ml. aliquots of one of the above buffer solutions were placed in eight 5.0-ml. volumetric flasks, 1.0 ml. of 0.016, 0.020, 0.028, 0.032, 0.040, 0.060, 0.10 and 0.20 M urea solution added to successive flasks and the latter placed in a bath at 25 * 0.02'. After thermal equilibrium was obtained 0.78 (18) 0. H. Straus and A. (21) E. J Conway, "Micro-diffusion Analysis and Volumetric Error," D Van Nostrand Co , New York, M. Y , 1940, p 73ml. of a diluted enzyme solution was added to each of the above solutions and the mixtures vigorously stirred with a rod kept in each flask. After 3 minutes 0.5 ml. of 2.0 N sulfuric acid was added to each flask, the solution again stirred, the flasks withdrawn from the bath, the stirring rods washed and the volume of solution in each flask made up to 5.0 ml. The diluted enzyme solutions were prepared so as to contain approximately 1 microgram of protein nitrogen per ml. of solution. These solutions which were 0.01 M in the appropriate buffer were allowed to stand for 5 hours a t 25' prior to use. For the determination of liberated ammonia 1.0-ml. aliquots of approximately 0.005 N hydrochloric acid containing Tashiro indicator*' was placed in the central chamber of a Conway dish, a 1.0-ml. aliquot of one of the above 5.0 ml. solutions placed in the outer chamber, the lid, lubricated with glycerol containing sodium hydroxide, placed in position so as to permit the rapid intr...

No abstract

Analogues of folic acid having the pteridine ring replaced by quinazoline have been prepared by reductive condensation of appropriately substituted quinazoline-6-carbaldehydes and -carbonitriles with diesters of N-(p-amino-benzoy1)amino-acids, followed by hydrolysis.Davis, and Company, Hounslow, Middlesex (I ; R1 = OH, R2 = H) antagonists R1 = NH,, R2 = H) and methotrexate (I ; Ri = NH,, R2 = Me) were among the earliest known compounds to show activity against acute leukaemia ; the latter is still used both for this purpose and as an immune suppressant. In view of this, the synthesis of potential antagonists derived from quinazoline (ie. ' 5,8-dideazapteridine ') was undertaken.Three types of variant were required: (a) Z-amino-4-hydroxy-or 2,4-diamino-substituted derivatives, (b) derivatives containing different terminal amino-acids, and (c) 5-substituted derivatives, since the 5-position in folic acid is involved in its biochemical functions.The 4-amino-4-deoxy-analogue (11; R = C0,H) of pteroic acid in this series has been synthesised previously 1 by the reaction of 2,4-dibenzamido-6-bromomethylquinazoline with ethyl 9-aminobenzoate, followed by removal of protective groups, and we initially attempted the synthesis of (111; R = H, n = 2), the quinazoline analogue of aminopterin, by using diethyl fV-(p-aminobenzoy1)-L-glutamate in this synthesis. However, almost complete hydrolysis of one aminogroup (presumably that at position 4) occurred, during either the condensation or the subsequent hydrolysis of the protecting groups, to give principally (IV; n = It seemed likely that a reductive condensation between a quinazoline-6-carbaldehyde or -carbonitrile and an N-(p-aminobenzoyl) amino-acid ester would proceed under milder conditions, and moreover, since heterocyclic amino-groups such as those present in 2,4-diaminoquinazoline do not readily give Schiff bases, preliminary protection of these groups would be unnecessary.2,4-Diaminoquinazolines have usually been prepared

and the quinine equiv Q (the ratio of the SD90 of quinine-HC1 to the SD90 of the test substance under comparable exptl conditions). 2,4-Diamino-6- [(benzyl)aminb] pyrido [2,3-d]pyrimidine (Via) and 2 ,4-diamino-6-[(3,4-dichlorobenzyl)amino] pyrido [2,3-d] pyrimidine (VIb) lacked significant antimalarial effects at daily doses of 325 and 171 mg/kg, respectively, and were therefore <20 times as potent as the corresponding quinazoline analog 2,4-diamino-6-[(3,4-dichlorobenzyl)amino] quinazoline (la).2 2,4-Diamino-6-[(3,4-dichlorobenzyl)nitrosamino] pyrido [2,3-d]