Reactions of 2-, 6-, and 8-monosubstituted 1- and 3-methylpurines with hydroxide ions in water

摘要

1976 151Reactions of 2-, 6-, and 8-Monosubstituted 1 - and 3-Methylpurines withHydroxide Ions in WaterBy Rodney J. Badger and Gordon B. Barlin," Medical Chemistry Group, John Curtin School of MedicalThe reactions of 2-, 6-, and 8-monochloro- (or methylthio-) 1 -(and 3-) methylpurines towards N-sodium hydroxidehave been examined. 1 -Methyl-2- and -6-methylthiopurine underwent normal nucleophilic displacement to givethe hydroxypurines, but 1 -methyl-8-methylthiopurine underwent ring fission to give 5-amino-Z-methylthioimid-azole-4-carbaldehyde. 3-Methyl-6-methylthiopurine afforded 5-methylaminoimidazole-4-carbaldehyde pre-dominantly, and some 6-hydroxy-3-methylpurine; and 3-methyl-8-methylthiopurine underwent ring openinglike its 1 -methyl isomer. 7- ( and 9-) Methyl-2-methylthiopurines (for comparison) gave 4-amino-5-methyl-amino- and 5-amino-4-methylamino-2-methylthiopyrimidines, respectively.6-Chloro-3-methylpurine gave5-methylaminoimidazole-4-carbonitrile and some 6-hydroxy-3-methylpurine; but 8-chloro-3-methylpurinewas consumed without forming 8- hydroxy-3-methylpurine.Research, Australian National University, Box 4, Canberra, Australia 2600REACTIONS of 2-, 6-, and 8-chloro- and methylsulphonyl-7-(and 9-)methylpurines with hydroxide ions have beenrecorded previous1y.l The nucleophilic displacementand ring-opening reactions of some 2-, 6-, and 8-mono-chloro-(or methylthio-) 1-(and 3-)methylpurines towardshydroxide ions have now been examined. A number ofpurines and purinium salts 34 alkylated in the pyr-imidine ring are known to undergo ring opening underalkaline conditions to give imidazoles; the productsfrom 3-me t hyl-6,8-bismethylthiopurine (1) with hy-droxide ions were not identified.5In the present work l-methyl-2- and -6-methylthio-purines were heated with N-sodium hydroxide on as team-ba t h, giving 2- and 6-hydroxy- 1 -met hylpurine ,respectively, as the only products, but l-methyl-8-methylthiopurine (2) under the same conditions under-went a two-step process as indicated by the U.V.spectraR. J . Badger and G. B. Barlin, J.C.S. Perkin 11, 1974, 1854.B. C. Pal and C. A. Horton, J. Chem. SOC., 1964, 400.J. W. Marsico and L. Goldman, J. Org. Chem., 1965, SO, 3597.D. J . Brown and P. W. Ford, J. Chem. SOC. (C), 1969, 2620.5 U.Reichman, F. Bergman, D. Lichtenberg, and 2. Neiman,J . Org. Chew.. 1973, 38, 2066152 J.C.S. Perkin Ito give ultimately 5-amino-2-methylthioimidazole-4-carbaldehyde (3), together with a gaseous base, assumedt o be methylamine. The reaction presumably pro-ceeded by nucleophilic attack by hydroxide ion at C-2.( 2 ). .IOHC 7-N( 3)A check of the stability of 2-, 6-, and 8-hydroxy-l-(and 3-)methylpurines under the conditions of thehydrolysis revealed that they were stable. The structureof (3) was established by analysis, lH n.m.r. spectra, andits ring closure with formamide at 190-200 "C to give8-methylthiopurine. Compound (3) shows an unusuallylong wavelength U.V. absorption maximum (at 330 nm).3-Methyl-2-methylthiopurine was not available forstudy.3-Methyl-6-methylthiopurine with N-sodiumhydroxide underwent ring opening to give 5-methyl-aminoimidazole-4-carbonitrile predominantly, contraryto the findings of Jones and Robins,6 and possibly asmall amount of 6-hydroxy-3-methylpurine as shownby paper chromatography. This reaction is also en-visaged as proceeding by hydroxide ion attack at C-2followed by elimination of the methylthio-group ; themechanism is similar to that proposed in the pteridineand quinazoline series7 3-Methyl-6-methylthiopurinewith the stronger nucleophile, methoxide ion, underwentreplacement only to give 6-methoxy-3-methylpurine.An attempt to oxidize 3-methyl-6-methylthiopurine tothe corresponding sulphone with potassium perman-ganate in 8N-acetic acid gave only 6-hydroxy-3-methyl-purine, formed presumably by hydrolysis of the methyl-sulphonyl group.Repetition of the work of Pal andHorton under less severe conditions revealed that6-amino-met hylpurine and N-sodium hydroxide at75-80 "C for 30 min gave mostly 6-hydroxy-3-methyl-purine and no amp;met hylaminoimidazole-4-carbonit rile.3-Methyl-8-methylthiopurine with N-sodium hydroxideunderwent ring opening like its l-methyl isomer to givea product tentatively identified as 5-methylamino-2-methylthioimidazole-4-carbaldehyde on the basis ofits lH n.m.r. and mass spectra and similarity in U.V.spectrum to compound (3).J. W. Jones and R. I. Robins, J . Ainer. Chcm. SOC., 1962,84,1914.7 E. C. Taylor, R.J. linopf, J. A. Cogliano, J. W. Barton, andW. Pfleiderer, J- Anzer. Chem. SOC., 1960, 82, 6058.8 D. J. Brown, R. L. Jones, A. M. Angyal, and G. W. Grigg,J.C.S. Pevkin I , 1972, 1819.G. R. RarIin, J . Chetn. SOC. ( B ) , 1967, 954.lo C . 0. Johns. T . Biol. Chern.. 1912,11, 73.For comparative purposes both 7- and 9-methyl-2-methylthiopurines with N-sodium hydroxide were ex-amined, and gave respectively 4-amino-Ei-methylamino-and 5-amino-4-methylamino-2-methylthiopyrimidine.(Brown and Jones * found that 6,9-dimethyl-2-methyl-thiopurine with N-sodium hydroxide at 100 "C gave5-amino-4-methyl-6-methylamino-2-methylthiopyr-imidine.) 2-Dimethylamino-9-methylpurine under simi-lar conditions did not undergo appreciable change,presumably owing to electron release by the substituentand relative stabilisation of the nucleus to nucleophilicattack.By contrast 7- and 9-methyl-2-methylsulph-onylpurines with hydroxide ion underwent normalnucleophilic displacement ,l and 2-chloro-7-methyl-purine gave a mixture of the hydroxypurine and4-amino-2-chloro-5-methylan~inopyrimidine.Of the chloro-N-methylpurines examined in thiswork 6-chloro-3-methylpurine with N-sodium hydroxideat ca. 80 "C as described in the Experimental sectiongave 5 -met hylaminoimidazole-4- car bo ni t rile and alsosome 6-hydroxy-3-methylpurine; the reaction mixturefrom 8-chloro-3-methylpurine under comparable con-ditions revealed no evidence of 8-hydroxy-3-methyl-purine on chromatographic and U.V. spectroscopicexamination ; and 2-chloro-9-methylpurine 9 gave twomajor products, one of which was shown by chromato-graphy to be 2-hydroxy-9-methylpurine.Preparation of Conzpozcnds.-Compounds required forthis study but not described in the Experimentalsection were prepared as follows. 2-Hydroxy-l-methyl-purine lo was produced from 4-amino-2-hydroxypyr-imidine through its 5-nitro-derivative,11 4-amino-l-methyl-5-nitropyrimidin-2-one,12 4,5-diamino-l -met hyl-pyrirnidin-2-one,l3 and its 5-formyl derivative.I06-Hydroxy-l-methylpurine l4 was prepared from ethylcyanoacetate and thiourea through 4-amino-6-hydroxy-2-mer~aptopyrimidine,~~ its 6-nitro-derivative,15 4,5-diamino-6-hydroxy-2-mercaptopyrimidine,15 its 5-f ormylderivative ,15 4-amino-5-f ormylamino-6-hydroxypyr-imidine,14 and its N(l)-rnethyl derivative.14 8-Hydroxy-I-methylpurine l6 came from 4-amino-6-hydroxypyr-imidine through 4-amino- 1-metliylpyrimidin-6-one asdescribed below, its 5-nitro-derivati~e,~~ 4,5-diamino-l-methylpyrimidin-6-0ne,~7 6,8-dihydroxy-l-methyl-purine ,I7 and 8- hydroxy-6-mercap t o- 1 -methylpurine .162-Hydroxy-3-methylpurine l8 was prepared from N-methylurea and ethyl nitrosocyanoacetate l9 through4-amino-6-hydroxy-3-metli~~l-5-nitrosopyr~m~din-2-0ne,~~4,5-diamino-6-hydroxy-3-methylpyriinidin-2-0ne,~~ 2,6-13 1.J. FTX and D. van Praag, J . Ovg. Chem., 1961, 26, 526.l4 G. B. blion, J . Org. Chent., 1962, 2'9, 2478.l5 W. Traube, Annaien, 1904, 331, 64.16 D. Lichtenbera. F. Bergmann, $1. Rahat, and 2. Neiman,J.C.S.Pevkin I , 1972, 2980. -l7 D. J. Brown and J. S. Harper, J . Chem. SOC., 1961, 1298.l8 F. Bergmann, G. Levin, A. Kalmus, and H. Kwietny-Govrin,l1 C. 0. johns; Amer. Chsl-n. J . , 1911, 45. 79.l2 C. 0. Johns, J . Biol. Chela., 1914, 1'4, 1.J Org. CheG., 1961, 26, 1504.Chem. (Japmz), 1962, 28, 624.1950, 83. 201.Is J. A. Sprung, U.S.P. 2,636,960 (Chem. Abs., 1953,47,8566d).2o C. Liau, I. Yamashita, and M. Matsui, Agric. and Biol.21 H. Bredereck, H.-G. bsol;.'on Schuh, and A. Martini, Clzem. Ber.1976 153dihydro~y-3-methylpurine,~l and 2-hydroxy-6-mer-capt0-3-rnethylpurine.~s An alternative preparation of2,6-dihydroxy-3-methylpurine 22 from ' sulphamino-uracil ' z2- (5-aminouracil-6-sulphonic acid) throughits N-methyl derivative 22 was unsatisfactory becauseof difficulties associated with the methylation.6-Hydroxy-3-methylpurine l8 was prepared from N-methylthiourea and ethyl cyanoacetate through 4-amino-6-hydroxy-3-methylpyrimidine-2-thione 26 andits 5-nitroso-derivative,27 5,6-diamino-4-hydroxy-1-metliylpyrimidine-2-thione 27 and 6-hydroxy-2-mer-cap t o-3-me t h ylpurine 8-Hydroxy-3-me t hylpurine l8was prepared from 5,6-diamino-4-hydroxy- l-methyl-pyrimidine-2-thione 27 through 5,6-diamino-4-mercapto-l-methylpyrimidine-2-thione 27 and 8-hydroxy-2,6-di-lnercapt o-3-methylpurine .27 2-, 6- Or 8-chloro-l-methyl- or 2-chloro-3-methyl-purine could not beprepared from the corresponding hydroxy-compoundswith phosphoryl chloride and diethylaniline under avariety of conditions, nor could 2-chloro-1-methylpurinebe prepared from the hydroxy-compound with theBosshard reagent .28-30 8-Chloro-3-methylpurine wasprepared, but in low yield, from 8-hydroxy-3-methyl-purine with phosphoryl chloride and diethylaniline.Satisfactory analyses could not be obtained but the lHn.m.r.and mass spectra were consistent with itsstructure. 6-C hloro-3-me t h ylpurine 31 (as hydro-chloride) was prepared by the literature procedure 31from 3-methyl-6-methy1thiop~rine.l~ l-Methyl-2-methylthiopurine was prepared from 4,5-diamino-l-methyl-2-methylthiopyrimidinium iodide 32 through 4,5-diamino-l-methylpyrimidin-2-thione and 2-mercapto-1 -methylpurine as described below. The preparation inaqueous sodium hydroxide was unsatisfactory owing todeformylation.An attempted preparation involvingthe quaternisation of 4,5-diamino-2-benzylthiopyrimidinewith methyl iodide was unsatisfactory.1-Methyl-6-met hylthiopurine hydriodide was preparedaccording to a published method 33 and l-methyl-8-methylthiopurine was obtained from its hydri~dide.~~Attempted preparation of the latter from 4,5-diamino-l-methylpyrimidinium chloride with thiourea gave instead1,4-dihydro-4-irnino-l-met hyl-5-thioureidopyrimidine.2-Mercapto-3-methylpurine could not be preparedfrom the 2-hydroxy-analogue by reaction with phos-phorus pent asulphide in pyridine or tetralin. 3-Methyl-8-methylthiopurine was prepared by methylation of8-metlrylthiopurine with diazomethane (all four mono-methyl isomers were obtained).22 H.Bredereck and A. Edenhofer, Chern. B e y . , 1956, 88, 1306.s3 I?. G. Fischer, W. P. Neumann, and J. Roch, Chew. Ber.,24 C . D. Nenitzescu, M. Avram, and E. Sliam, Rev. Chim.25 D. J. Brown, ' The Pyrimidines, Interscience, London, 1962,26 W. Traiibe and F. Winter, Arch. Pharm., 1906, 244 1127 G. Levin, A . Kalmus, and F. Bergmann, J . Org. Cheln., 1960,28 H. H. Bosshard, K. Mory, M. Schmid, and H. Zollinger,1952, 85, 752.(Rouwaania), 1966, 1, 73 (cf. Chem. A?., 1957, 51, 1973).p. 145.Chem. Zefltr., 1906, 6(1), 13361.25, 1752.Helv. Chim. Acta, 1969, 42, 1653.EXPERIMENTALAll compounds were examined for impurities by paperchromatography on Whatman no. 1 paper with (a) aqueous3 ammonium chloride, and (b) butan- l-ol-5~-acetic acid(7 : 3) as solvent, and by t.1.c.and were recrystallised toconstant m.p.Analyses were performed by the Australian NationalUniversity Analytical Services Unit. Solids for analysiswere dried at 100 "C unless otherwise stated and m.p.swere taken for samples in Pyrex capillaries. U.V. spectrawere measured with a Unicam SP 1700 spectrophotometer.1H N.m.r. spectra were recorded at 60 MHz and 35 "C witha Varian T-60A spectrometer, with 2H,dimethyl sulph-oxide as solvent and tetramethylsilane as internal standard.1.r. spectra were determined for Nujol mulls. Mass spectrawere measured by Dr. J. K. MacLeod with an A.E.I. MS9instrument.Hydrolysis experiments were conducted a t 75-80 "Cand also (for spectroscopic concentrations) a t 20 "C; bothgave similar results as shown by the spectra.5-Aminozamp;raciamp;6-sul~ho~ic A cid .-This compound wasprepared according to the literature procedures.22-25Methylation 24 of its sodium salt with methyl iodide gave aproduct apparently identical with that described byNenitzescu,2* which has a lH n.ni.r.spectrum consistentwith a ring-methylated structure (S(CD,),SO 3.2 (MeN)and 3.3 (s, Me,N); G(Na0D) 2.75 (Me,N) and 3.2 (MeN))rather than that of the trimethylamnionio-compound.244-A mino- l-~~.ethyZpyrimidin-6-one.-This compound wasprepared by modification 35 of the reported methylation of4-amino-6-hydroxypyriniidine with dimethyl sulphate inaqueous alkali.38 By altering the concentrations andallowing the reaction mixture to cool slowly, a precipitateof pure 4-amino-l-methylpyrimidin-6-one (20-30) yieldwas obtained.However extraction of the residue leftafter evaporation of the reaction mixture with chloroformyielded a mixture which also contained l-inethyl-4-methyl-aminopyrimidin-amp;one (possibly formed by methylation,Dimroth rearrangement, and remethylation), identified bymixed m.p. and i.r. spectral comparison with an authenticspecimen. l72-Hydroxy-3-~zethyZ~uri~ze.-3-Rlethyl-6-thiosantliine (3.6g) was dissolved in 0.75~-sodium hydroxide (50 nil) andrefluxed with Raney nickel (ca. 14 g wet) for 2.5 h. Thenickel was filtered off and the filtrate adjusted to pH 6with 10whydrochloric acid and evaporated to dryness.The residue was extracted several times with boilingethanol and gave 2-hydroxy-3-methylpurine (1.18 g)S(CD,),SO 3.57 (MeN) and 8.10 and 8.61 (each s, 8- and6-H) ; its U.V.spectrum corresponded with publisheddata.37 Bergmann and his co-workers l8 report a yieldof 120/,.M. Ikehara, H. Uno, and I;. Ishikawa, Chem. and Pharm.3O J. TemliEka and F. Sorm, Coll. Czech. Chem. Cornm., 1966,31 I?. Bergmann, 2. Neiman, andM. Kleiner, J . Cheutz. SOC. (C),32 D. J. Brown and N. W. Jacobsen, J . Chem. SOC., 1962, 3173.a3 F. Bergmann, M. Kleiner, 2. Neiman, and M. Rashi, Israel34 U. Reichman, F. Bergmann, D. Lichtenberg, and 2. Neiman,36 D. J. Brown and J. S. Harper, unpublished work.36 W. Pfleiderer and E. Liedek, Amzalen, 1958, 812, 163.37 F. Bergmann, H. Kwietny, G.Levin, and D. J. Brown, J .Bull. (Ja#an), 1964, 12, 267.30, 1880.1966, 10.J . Chew., 1964, 2, 185.J.C.S. Perkin I , 1973, 793.Amer. Chem. Soc., 1960, 82, 598J.C.S. Perkin I8- Chloro- 3-methylpurine .-A mixture of 8-hydroxy-3-methylpurine (0.155 g), phosphoryl chloride (3.5 ml), anddiethylaniline (0.4 ml) was refluxed with stirring for 2.5 h.Solid began separating after 0.5 h. The mixture wasevaporated in vacuo, the dark oil was cooled in ice, waterwas added, and the solution was adjusted to pH 3 withammonia and extracted with chloroform (3 x 20 ml).The product (contaminated with diethylaniline) wassubjected to t.1.c. (alumina; chloroform) and the productrecrystallised from cyclohexane to give S-chloro-3-methyl-puvine, m.p.140-145" (decomp.), G(CDC1,) 4.26 (MeN) and8.5 and 8.91 (2- and 6-H), Mf 168/170.4,5-Diamino- l-inethylpyrimidine-2-thzone .-To a solutionof sodium ethoxide from sodium (0.75 g) and ethanol(40 ml) saturated with hydrogen sulphide was added asuspension of 4, 5-diamino- l-metliyl-2-methylthiopyrimidin-ium iodide 32 (4.6 g) in ethanol (40 nil). This mixturewas heated under reflux for 1 h with hydrogen sulphidecontinuously bubbled through. A white solid whichdeposited was collected and recrystallised from ethanol togive 4,5-diamino-l-meeuro;hylpyrimidine-2-thione (1.98 g), m.p.265-267" (decomp.) (Found: C, 38.8; H, 5.2; N, 36.0.C,H,N,S requires C, 38.5; H, 5.2; N, 35.9y0).2-Mercapto- l-utzethyl$wrine.-(a) 4-Amino-5-formamido-1-methylpyrimidine-2-thione (0.43 g), NN-diniethylform-amide (5.0 ml), and anhydrous potassium carbonate (0.43 g)were refluxed for 1.5 h.The mixture was diluted withwater and adjusted to pH 7, and the product (0.33 g) wascollected and recrystallised from water to give 2-merca$~to-l-methylpurine, m.p. 285-290" (decomp.) (Found : C,43.3; H, 3.9; N, 33.9. C,H,N,S requires C, 43.4; H, 3.7;(b) 4,5-Dianiino-l-methylpyrimidine-2-thione (0.040 g)and formamide (0.5 ml) were heated a t 190 "C for 10 min.The mixture was cooled and the product collected and re-crystallised from water; it was identical with that describedin (u).(c) 4,5-Diamino-l-methylpyrimidine-2-thione (0.25 g) andformic acid (98 ; 5 ml) were heated under reflux for 6 h,The solution was evaporated to dryness in V ~ C U O and theresidue was heated under reflux with B~-sodium hydroxide(6.0 ml) for 20 min, and acidified with acetic acid.Theprecipitate was collected and recrystallised from water togive 2-mercapto-l-methylpurine (0.095 g), m.p. 285-290'(decomp.). Repetition of the experiment gave a low yieldof 2-mercapto-l-methylpurine and 4,5-diamino-l-methyl-pyrimidine-2-thione was recovered from the reactionmixture.4-Anzino-6-forma~~ido-l-methyl~y~imidiuze-2-tkione.- Amixture of 4,5-diamino-l-methylpyriniidine-2-thione (0.500g ) and formic acid (10 ml) was refluxed for 1.5 h and thenevaporated to dryness. The residue was diluted withwater and adjusted to pH 6, and the solid collected andrecrystallised from water to give the fovmaPtziclopyrimidilze(0.430 g), m.p.270-275" (decomp.) (Found: C, 39.4; H,4.2; N, 30.6. C,H,N40S requires C, 38.1; H, 4.4; N,30.4).l-Methyl-2-methylthiopurine.- 2-Mercapto- l-methyl-purine (0.095 g) dissolved in 0. IN-sodium hydroxide (8.0 rnl)was stirred vigorously with methyl iodide (0.2 ml) for 3 h.The product (0.090 g) was filtered off and recrystallised fromwater to give l-a~zeth~~l-2-methylthio~urine, m.p. 243-245'(Found: C, 46.5; H, 4.5; N, 31.4. C,H,N,S requires C,46.6; H, 4.5; N, 31.1).4,5-Diamino-2-benzylthiopyrimidine.-Benzyl chlorideN, 33.7).(0.57 ml) was added dropwise with stirring over 1 h to asolution of 4,5-diamino-2-mercaptopyrimidine (0.5 g) in2~-sodium hydroxide (4.25 ml) and stirring was continuedfor 3 h. The precipitate was colIected and recrystallisedfrom water to give 4,5-diarazino-2-benzylthiopy~imidine(0.42 g), m.p.151-153" (Found: C, 56.8; H, 5.3; N, 24.1.C,,H,,N,S requires C, 56.8; H, 5.2; N, 24.1).l-Met~z~1-8-methylthiopurine.- l-Metliyl-S-methylthio-purine hydriodide 34 (0.500 g) was converted into thehydrochloride by shaking with an excess of freshly preparedsilver chloride. After filtration the solution of the hydro-chloride was adjusted to pH 6 with 2~-sodium hydroxideand evaporated to dryness. The residue was extractedseveral times with boiling ethyl acetate and on concen-tration gave l-methyl-8-methylthiopurine (0.150 g), m.p.218-220" (Found: C, 46.75; H, 4.7; N, 31.2. C,H,N,Srequires C, 46.6; H, 4.5; N, 31.1).1,4-Di Jzydro-4-imino- I-methyl-5-thioureidopyvimidine.-4,5-Diamino- 1-methylpyrimidinium chloride 32 (0.2 g) andthiourea (0.3 g) were fused a t 185-190 "C for 15 min. Themixture was diluted with water, adjusted to pH 7, andevaporated to dryness. The residue was dissolved inN-sodium hydroxide and neutralised with acetic acid ; thecrystals which were slowly deposited were collected andrecrystallised from ethanol to yield l14-dihydro-4-imino- 1-.methyl-5-thioureidopyrimidine (0.015 g) (Found : C, 39.4 ;H, 5.5; N, 37.6.C,H,,N,S requires C, 39.1; H, 5.4; N,38.0), v,,~ 2 080 cm-l.Methylation of 8-Methylthiopurine with Diazomeeuro;hane.-8-Methylthiopurine 38 (1.5 g ) was suspended in ether (50 ml)containing diazomethane (ca. 1.5 g) and the mixturestirred a t room temperature for 20 h.The precipitate(0.800 g) was filtered off and subjected to t.1.c. alumina;chloroforni-ethanol (30 : l) to give, in order of descendingRF value, the 9-, 7-, 3-, and 1-methyl isomers. The 9-, 7-,and l-methyl isomers were identified by i.r. and 1H n.m.r.comparisons with authentic specimens,l, 39 and the 3-methylisomer by m.p. and U.V. comparison with published data.4The filtrate from the preparation was evaporated and theproduct chromatographed on an alumina column. 9-Methyl-8-methylthiopurine was eluted first, and thesolvent was changed to chloroform-ethanol (30 : 1) to givethe 3-methyl isomer. The overall yields of isomers were9- (0.41 g), 3- (0.255 g), 7- (0.150 g), and 1- (0.250 g).Hydrolysis of l-Methyl-2-methylthiopurine.-l-Methy1-2-methylthiopuriiie (0.01 g) and N-sodium hydroxide (1.0 ml)were warmed on a steam-bath for 20 min, cooled, andneutralised.Paper chromatography revealed one productonly, identical with authentic 2-hydroxy-l-methylpurine,1deg;and the U.V. spectra were also consistent with this product.13Hydrolysis of l-Methyl-6-~nethylthiopurine.-ll-NIethyl-6-mcthylthiopurine hydriodide (0.010 g) and N-sodiumhydroxide (1.0 ml) were heated a t 75-80 "C for 15 min,cooled, and neutralised. Paper chromatography showedone product only of the same I;)* value as l-methyl-hypoxanthine. The spot was eluted and the U.V. spectrawere found consistent with published data for l-methyl-hypoxanthine l4 A,,, 249 nm (pH O.O), 251 (5.0), and260 (ll.O).Methyl-8-methylthiopurine (0.1 g) and N-sodium hydroxide(1.0 ml) were heated on a steam-bath for 20 min.Themixture was cooled and neutralised and the precipitate5-A mino-2-methylthioimidazole-4-ca~baldehyde.- 1-38 A. Albert and D. J. Brown, J . Chewz. SOG., 1954, 2060.aB D. J. Brown and S. F. Mason, J . Clcem. SOC., 1957, 6821976 155(0.023 g) collected and recrystallised from water to give5-amino-2-methylthioirnidazole-4-carbaldehyde, m.p. 90-91"(Found, for sample dried a t 70 "C and 20 mmHg: C , 38.4;H, 4.8; N, 26.3. C,H,N30S requires C, 38.2; H, 4.5; N,26.7), 6(CD,),SO 2.53 (MeS) and 9.01 (HCO), M+ 157,A,,, (pH 12) 330 nm..5-Methylnnzinoiz~iidazole-Ccarbonitrile.- 3-Metliyl- 6-methylthiopurine l8 (0.1 g) and N-sodium hydroxide (1.0 ml)were heated on a steam-bath for 30 min.The mixture wascooled and neutralised, and the solid collected and re-crystallised from water to give 5-methyEanziv~oirnidazole-4-carbonitrile (0.035 g), m.p. 222-223" (Found: C, 49.1;H, 4.S; N, 46.4. C,H,N, requires C, 40.2; H, 4.9; N,45.9), 6(CD,),SO} 2.83 (d, MeN) and 7.11 (Z-H), v,,,2 220 cni-1 ( E N ) , M+ 122.6-Methoxy-3-rnethylpurine.-A mixture of 3-methyl-6-methylthiopurine (0.08 g) and sodium methoxide (0.25~ ;8 nil) was refluxed for 0.5 h, then cooled, and dry hydrogenchloride was passed through until precipitation was com-plete. The mixture was evaporated in vaczto and a solutionof the residue in water was adjusted carefully to pH 9.The precipitate was collected and recrystallised from watert o give 6-methoxy-3-methylpurine dihydrate, m.p.160-162" (lit.,31 160-162") (Found: C, 50.1; H, 5.3; N, 33.45.Calc. for C,H,N40,0.2H,0: C, 50.1; H, 5.05; N, 33.4).Hydrolysis of 3-MethyZ-8-methylthiopurine.-3-Methyl-8-methylthiopurine (0.020 g) and N-sodium hydroxide (2.0 ml)were warmed a t 75-80 "C for 6 inin. The mixture wasthen adjusted to pH 6 and extracted with chloroform.The product was subjected to t.1.c. (alumina; chloroform-ethanol) and the major spot eluted with chloroform, but onconcentration i t darkened to give a solid, m.p. 25-35",M+ 171 (Calc. for C,H,N,OS: M , 171). The U.V. spectrumat pH 11-13 was similar to that for 5-amino-methyl-thioimidazole-5-carbaldehyde from l-methyl-8-methylthio-purine,Hydrolysis of 7-Methyl-2-methylthiopurine.-7-Methyl-2-methylthiopurine (0.005 g) and wsodium hydroxide (1.0ml) were warmed a t 75-80 "C for 0.5 h.The mixture waschilled and the solid (0.0032 g) was collected; i t wasidentical with authentic 4-aniino-5-methylamino-2-methyl-thiopyrimidine 40 mixed m.p. 203-205" (lit .,40 202-204") ;lH n.m.r., u.v., and i.r. spectroscopy. Paper chromato-graphy of the reaction mixture and the precipitate did notreveal any 2-hydroxy-7-methylpurine.1Hydrolysis of O-Methyl-2-metlzyZthio~u~ine.-9-Methyl-2-methylthiopurine (0.010 g) and N-sodium hydroxide (1.0 ml)were heated a t 75-80 "C for 0.5 h; the mixture wasneutralisecl and evaporated to dryness. The product wasidentical (paper chromatography and lH n.m.r.(CD,),SO)40 D. J. Brown, J . AppL Chem., 1965.5, 358.41 D. J. Brown, J . Appl. Chenz., 1957, '4, 109.with authentic 5-aniino-4-methylamino-2-methylthiopyr-imidine (described below).5-Ami~zo-4-methylanzino-2-met~~yltkio~yri~Mzidine.- 5-Aniino-2-mercapto-4-methylaminopyrirnidine 41 (0.5 g) dis-solved in N-sodium hydroxide (8.0 ml) with methyl iodide(0.5 ml) was stirred vigorously a t room temperature for 1 h.The solid which separated was collectccl, washed with alittle cold ethanol, and recrystallised from warm water togive 5-ailni.~zo-4-methylamino-2-nzet~~ylthio~y~~~~~dine (0.27 g) ,n1.p. 108-110" (Found, for compound dried a t 70" and 20mmHg: C , 42.6; H, 5.9; N, 33.4. C,HIoN4S requires C,42.35; M, 5.9; N, 32.9), S(CD,),SOJ 2.35 (MeS), 2.75(d, MeN, J 5 Hz), 4.37br (HN), and 7.38 (6-H).Hydrolysis of 2-Dimethylamino-9-methyZpurine.-2-Di-methylamino-9-methylpurine 42 (0.00 1 g) and wsodiumhydroxide (0.5 ml) were heated a t 75-80 "C.Paperchromatography after 30 min revcakd only startingmaterial; however after 1.5 h another product had beenformed but i t was not Z-hydro~y-9-iiiethylpurine.~~Hydrolysis of 6-ChZo~o-3-~nethylpurine.-6-Chloro-3-methylpurine hydrochloride 31 (0.015 g) and N-sodiumhydroxide (1.0 ml) were warmed at 75-80 "C for 20 min.The mixture was adjusted to pH T and on paper chromato-graphy showed two spots, the major one corresponding to5-methylaminoimidazole-4-carbonitrile (see above) and theother to 3-methylhypo~anthine.~~S-~ercaPtopul.ine.-(a) 1,4-Dihyclro-4-imino-l-methyl-5-thioureidopyrimidine (0.005 g) was fused a t 200-210 "C for0.5 h. The mixture was diluted with water and filtered,and the filtrate evaporated to dryness ; the 8-mercapto-purine, was identified by comparison (u.v. and i.r. spectra)with an authentic sample (Pfaltz and Bauer Inc.).(b) 4,5-Diamino- 1-methylpyriniidinium chloride 32 (0.4 g)and thiourea (0.65 g) were fused a t 200-210 "C for 0.5 h.The solid obtained after cooling was recrystallised fromwater to yield 8-mercaptopurine (0.16 g), identified by itsspectra.8-ll.irethyZthio~urine.- 5-Aniino-2-methylthioimidazole-4-carbaldehyde (0.015 g) and formamide (1.5 inl) were heateda t 190-200 "C for 0.5 h. The solution was subjected tot.1.c. (cellulose; butanol-acetic acid, 7 : 3) and the spot ofRF corresponding to authentic S-methylthiopurine 38743was removed and eluted with water. Evaporation of theextract gave 8-niethylthiopurine (0.003 g), which wasfurther characterised by its i.r. and U.V. spectra.We thank Drs. D. J. Brown and J. H. Lister for dis-cussions, and Mr. S. E. Brown for the lH n.m.r. spectra.One of us (R. J. B.) thanks this University for support as ascholar.6/1365 Received, 8th July, 1975142 G. B. Barlin and A. C. Young, J . Chew. SOC. (B), 1971, 821.43 S. F. Mason, J . Chew. SOC., 1954, 2071