2,884,667 United States Patent Office Patented May 5, 1959 1. 2 EXAMPLE 1. 2,884,667 2-amino-6-mercaptopurine 2-AMINo-6-MERCAPTOPURINE A mixture of 20 g. of guanine, 100 g. of phosphorus George H. Hitchings, Tuckahoe, and Gertrude B. Ellion, 5 pentasulfide and 500 ml. of pyridine was refluxed for six Bronxville, N.Y. hours. The pyridine was removed under reduced pres NoDrawing. Application June 20, 1955 sure and the residue boiled with 500 ml. of water for Serial No. 516,734 10 minutes. The pH was adjusted to 4 by the addition 1. Claim. (C. 260-252) of concentrated hydrochloric acid and the mixture was 0 chilled. The precipitate was filtered off, washed with The present invention relates to purine compounds and water and dried at 100°. This precipitate was extracted more particularly to 6-mercaptopurine compounds of ex four times with 200 ml. portions of concentrated am ceptional activity as inhibitors of micro-organisms. The monium hydroxide and the insoluble residue filtered off. compounds are active in this respect, in the inhibition of The ammoniacal solution was evaporated to 500 ml. to lactic acid bacteria and for their bacterio-static effect. 15 remove some of the excess ammonia and the solution Compounds of this nature are also valuable for their anti then acidified to pH4 by the addition of concentrated leukemic activity and in treating other forms of neo hydrochloric acid. The precipitate of 2-amino-6-mer plastic growth, as described in Patent No. 2,697,709, of captopurine (11.7 g.), was purified by solution in dilute which the present application is a continuation. Ad ammonium hydroxide and precipitation at pH 4. The vanced studies have disclosed that these derivatives are 20 product has a characteristic ultraviolet absorption spec of exceptional interest, and have related properties and trum with maxima at 255 and 345 mp at pH 1, and at value for the indicated applications. The compounds, 245, 270 and 322 mu at pH 11. particularly thioguanine, are useful in producing remis EXAMPLE 2 sions in acute leukemia. The compounds, however, do A mixture of 1 g of guanine, 3 g. of phosphorus penta not cure the condition. .. 25 sulfide and 50 ml. of quinoline was warmed to about The compounds of the present invention are members 120 for 45 minutes and then at 175 for 30 minutes. of the class represented by the general formula: After cooling slowly the solvent was decanted and the SE residue extracted with hot water and filtered. The solid 30 was warmed with 8N ammonium hydroxide and filtered. NE The filtrate was boiled until neutral during which time a dark granular precipitate was formed. This was re moved by filtration and washed with methanol. The al yield was 450 mg. of material possessing the ultraviolet where R and R' are selected from the class consisting of absorption spectrum of 2-amino-6-mercaptopurine, as H, lower alkyl and aryl radicals; RRN is selected from 35 given above. the class consisting of cyclic amino radicals; and R and EXAMPLE 3 R together have no more than six carbon atoms. Compounds of this nature may be conveniently pre 2-dimethylamino-6-hydroxypurine pared by the reaction of a compound having the for A mixture of 30 g. of 2-methylmercapto-6-hydroxy mula: 40 purine and 100 ml. of a 25% solution of dimethylamine in methanol was heated in a sealed tube at 140 for 24 OH hours. The precipitate was filtered off and washed with methanol. The crude 2-dimethylamino-6-hydroxypurine NE (11 g) was recrystallized from 1 liter of water and de 45 colorized with Darco. The purified product (6.3 g) ...Old showed an ultraviolet absorption spectrum with M wherein RRN has the indicated values with phosphorus max. =258, 290 (infi.) mp at pH 1, and A max.s-245, pentasulfide in a basic solvent which is inert to the 280 mps at pH 11. phosphorus pentasulfide. This reaction can be carried EXAMPLE 4 out in an inert solvent such as tetralin, but the yields 50 are less satisfactory. 2-dimethylamino-6-mercaptopurine ... Suitable bases for the purpose are those relatively A mixture of 5.5 g. of 2-dimethylamino-6-hydroxy inert toward the reagents entering into the reactions and purine, 25.g. of phosphorus pentasulfide and 250 ml, of preferably those boiling over 100', allowing the reaction dry pyridine was heated under reflux conditions for 3 to proceed without the use of pressure equipment. Ef 55 hours. The reaction mixture was evaporated to dry fectively, for example, amino-substituted aromatic com ness under reduced pressure and the residue heated with pounds would be unsuitable because of their reactiveness 200 ml. of water for 20 minutes. After chilling, the under the conditions involved. Bases capable of operat solid residue was collected, washed with cold water and ing effectively under the conditions involved include dried at 90. The crude 2-dimethylamino-6-mercapto pyridines, picolines, lutidines, quinoline and perhaps iso 60 purine (3.75 g.) was purified by recrystallization from quinoline. Although the suitability of any number of Water followed by solution in 2-N hydrochloric acid bases for the purpose is easily ascertained, the avail reprecipitation by neutralization with ammonium hy. ability of pyridine makes this compound preferable in droxide. The purified product showed an ultraviolet the ordinary practice of the invention. In general the absorption spectrum with A max.-270 and 358 mpt heterocyclic bases may be preferred because they are suf 65 at pH 1 and A. max. =255, 283, 330 mu at pH 11. ficiently involatile, sufficiently basic and nonreactive to ward the components of the reaction. EXAMPLE5 The advantages of the present invention are improved 2-ethylamino-6-hydroxypurine yield, much greater ease of purification and greater con venience in manufacture due to the lower operating tem A mixture of 30 g. of 2-methylmercaptopurine-6-hy peratures which can be used. The following examples 70 droxypurine. and 100 ml. of 33% aqueous ethylamine are illustrative. , was heated at 140° in a sealed tube for 24 hours. The 2,884,667 3 4 Small insoluble residue was filtered off and the filtrate water and neutralization with ammonium hydroxide. ooncentrated to 50 ml. under reduced pressure. The The product has an ultraviolet absorption spectrum with solution was adjusted to pH 5-6 with acetic acid and A max.-260 mu, at pH 1 and N max. =255, 290 (infl.) the precipitate of 2-ethylamino-6-hydroxypurine col at pH 11. lected. After two recrystallizations from hot water, the 5 EXAMPLE 10 product (5.7 g.) showed an ultraviolet absorption spec trum with A max.-252, 275 (infi.) mu at pH 1 and A 2-piperidino-6-mercaptopurine max.-250, 275 mu, at pH 11. - A mixture of 7 g. of 2-piperidino-6-hydroxypurine, EXAMPLE 6 50 g. of powdered phosphorus pentasulfide and 500 mil. O dry pyridine was heated under reflux conditions for 3 2-ethylamino-6-mercaptopurine hours. The reaction mixture was worked up as de A mixture of 5.6 g. 2-ethylamino-6-hydroxypurine, scribed in Example 4. The 2-piperidino-6-mercapto 30 g. of phosphorus pentasulfide and 250 ml. of pyridine purine (4.1 g.) was purified by solution in dilute am was heated under reflux conditions for 4 hours. The monium hydroxide and precipitation at pH 5 with acetic mixture was taken to dryness under reduced pressure, 5 acid. The product has an ultraviolet absorption spec and the residue was heated with 100 ml of water for trum with A max.=272, 358 mu, at pH 1 and A max. 15 minutes. The solution was chilled and 150 ml. =255, 280, 328 mu, at pH 11. of concentrated ammonium hydroxide added. After further chilling the precipitate of ammonium phosphate EXAMPLE 11 was filtered off and the ammoniacal filtrate taken down 20 2-dimethylamino-6-mercaptopurine to 25 ml. under reduced pressure. Upon chilling, 2 A mixture of 15 g. of 2-methylmercapto-6-hydroxy: ethylamino-6-mercaptopurine (2.5 g) separated out and purine and 30 ml. of 30% methanolic dimethylamir was collected. The product has an ultraviolet absorpt was heated at 140° for 24 hours in a sealed tube. The tion spectrum with X max. =262 and 350 mu, at pH 1 mixture was taken to dryness under reduced pressure. and A max.=250, 325 mu, at pH 11. - 25 The residue was dissolved in 120 ml. of boiling 1-N hy drochloric acid filtered hot to remove an insoluble resi EXAMPLE 7 due. The filtrate was adjusted to pH 6 with ammonii 2-anilino-6-hydroxypurine hydroxide. After chilling, the 2-dimethylamino-6-hy A mixture of 30 g. of 2-methylmercapto-6-hydroxy 30 droxypurine (8.5 g.) was filtered off, washed with wa purine and 53 ml. of aniline was heated at 160° for 48 ter and dried at 110°. hours. The reaction mixture was diluted with 200 ml. A mixture of 5 g. of 2-dimethylamino-6-hydroxypurine, of absolute alcohol and the insoluble residue filtered 25 g. of phosphorus pentasulfide and 250 ml. of dry off. This residue was then leached with 200 ml. of pyridine was refluxed for three hours. The excess pyri ether and dried at room temperature. The crude 2 35 dine was removed by distillation under reduced pressure. anilino-6-hydroxypurine was isolated as its hydrochlo The residue was boiled with 200 ml. of water for 2 ride (25.1 g) by boiling with 200 ml. of 1-N hydro hour then chilled.