Pyrrolopyrimidine nucleosides. Part X. Synthesis of certain 4,5-disubstituted 7-(beta;-D-ribofuranosyl)pyrrolo2,3-dpyrimidines related to toyocamycin and sangivamycin

摘要

1248 J.C.S. Perkin IPyrrolopyrimidine Nucleosides. Part X. Synthesis of Certain 4 5D isu bst it uted 7- (@- D- R i bof u ranosyl ) pyrrolo 2,341 pyrimidines Related toToyocamycin and SangivamycinBy Barbara C. Hinshaw, Olga Leonoudakis, Karl H. Schram, and Leroy B. Townsend,. Department ofBiopharmaceutical Sciences and Department of Chemistry, University of Utah, Salt Lake City, Utah 841 12,U.S.A.The reactivity of the cyano-group of 4-chloro-7-(~-D-ribofuranosyl)pyrrolo2.3-dpyrimidine-5-carbonitrile (5)towards various nucleophiles has been studied. Although both exocyclic groups (CI and CN) reacted withvarious nucleophiles, the initial reaction was always a nucleophilic displacement of the 4-chloro-group, and thecyano-group reacted only after this had occurred.Additional studies on the reactivity of the 5-cyano-grouptowards various nucleophiles (MeNH,, NH,OH, HS-, MeS-), were conducted with groups other than CI a t C-4.The synthesis of 7-(P-D-ribofuranosyl) pyrrolo2,3-dpyrimidine-5-carbonitrile (1 0) is also reported. Studiescomparing the susceptibility towards nucleophilic attack of the 5-cyano-group of (1 0) with that of the 5-cyano-group of toyocamycin and deaminotoyocamycin (1 a) indicate that under both basic and acidic conditions thecyano-function of (1 0) is the more reactive.A RECENT investigation of certain pyrrolo2,3-dpyrimi-dines revealed that the group at C-4 (amino or 0x0) exertsa pronounced effect on the reactivity of a 5-cyano-grouptowards a nucleophile. The present investigation wasinitially designed to ascertain the effect which an electron-withdrawing substituent at C-4 would have on the re-activity of a 5-cyano-group towards nucleophilic addition.Treatment of 3,4-dihydro-4-oxo-7- (p-~-ribofuranosyl)-pyrrolo2,3-dpyrimidine-5-carbonitrile (la) with aceticanhydride-pyridine furnished a good yield of the2rsquo;,3rsquo;,5rsquo;-tri-O-acetate (lb) .Chlorination of (1 b) withphosphoryl chloride under conditions similar to thoseused previously3 in the tubercidin field furnished a goodyield of the 4-chloro-derivative (2). Treatment of (2)with methanolic ammonia at 0rdquo; effected complete re-moval of all blocking groups, as established by lH n.m.r.spectroscopy, to furnish the 4-chloro-5-cyano-nucleoside(5). That nucleophilic attack by ammonia at the cyano-group had not occurred was established by the strong i.r.absorption observed at 2 250 cm-l (C-N), and the reten-Chem., 1974, 11, 71.1 Part IX, A.F. Lewis and L. B. Townsend, J. HeterocycZiction of the 4-chloro group was shown by elemental analy-sis and U.V. and n.m.r. spectroscopy. The nucleoside (5),possessing an electron-withdrawing group at C-4 and acyano-group at C-5, was then exposed to a strong nucleo-phile under more stringent conditions to ascertain theinitial site of attack. Ethanolic piperidine at reflux tem-perature converted (5) into nucleoside material whichexhibited a strong i.r. absorption at 2 250 cm-l. The lHn.m.r. spectrum indicated a 1 : 1 ratio of the piperidylunit to the rest of the nucleoside, and elemental analysisestablished that reaction had occurred at only one of thepossible sites (C-4 or C-5).These data established thatdirect nucleophilic displacement of the 4-chloro-grouphad occurred, leaving the 5-cyano-group intact to furnishthe 4-piperidino-derivative (3b). Similar reaction con-ditions with different amines furnished 4-dimethylamino-(3a), 4-methylamino- (4a), and 4-ethylamino- (4b)derivatives. Treatment of (5) with an excess of sodium2 B. C. Hinshaw, J. F. Gerster, R. I. Robins, and L. B.Townsend, J . Org. Chem., 1970, 35, 236.8 J. F. GeTster, B. Carpenter, R. K. Robins, and L. B. Town-send, J . Medzcin. Chem., 1967,10, 3261975 1249methoxide in methanol at reflux temperature also resul- was used, the reaction was monitored by t.l.c., whichted in a simple displacement of the 4-chloro-group to showed that the initial step was a nucleophilic dis-afford the 4-methoxy-compound (4c) 6 4.12 (3H, s) ; v placement of the 4-chloro-group to yield (4d) ; this was2 250 cm-l.A selective displacement of the 4-chloro- followed by nucleophilic attack at the 5-cyano-group.group of (5) with 1 equiv. of hydroxylamine in ethanol at We had previously (see above) used an excess ofseveral nucleophilic reagents with only a displacementof the 4-chloro-group being observed ; however, thesefindings with hydroxylamine indicated that a change innucleophilic reagent might also effect a subsequent con-version of the cyano-group in this series of compounds.This prompted us to study the reactivity of the 5-cyano-group towards nucleophilic attack with a more stablegroup at C-4.Treatment of (4a) with hydrogen sulphideRO OR AcO OAc HO OH in pyridine-triet hylamine did indeed convert the cyano-group to afford the 4-methylamino-5-thiocarboxamide(7a). This was not unexpectedsince these nucleosides (3aand b) and (4a-c) are structurally similar to toyocamy-cin, which on treatment under these conditions is con-pyrimidine-5-thiocarboxamide (thiosangivamycin) .4-Et hylamino-7- (P-D-ribof uranosy1)pyrrolo 2,3-d-pyrimidine-5-thiocarboxamide (7b) was prepared from(4b) under essentially the same reaction conditions.Treatment of (5) with aqueous thiourea and a catalyticamount of formic acid furnished the 4-thione (8).That nucleophilic attack had not occurred at the cyano-group was established by elemental analysis and the ap-pearance of a strong i.r.band at 2 250 cm-l. Attempts toconvert the cyano-group of (8) with a nucleophile underbasic conditions proved unfruitful ; this behaviour cor-responds to that of (la) and the lack of reactivity isprobably due to the ease of ionization of the lactam orthiolactam system, respectively, under mild basicconditions. To circumvent this problem, we methylated(8) to obtain the 4-methylthio-derivative (9a). ThatS- rather than N-methylation had occurred was estab-lished by the hypsochromic shift observed in the U.V.spectra and the MeS signal (6 ca. 2.5) in the lH n.m.r.~pectrurn.~ The nucleoside (9a) could not support ananion in the pyrimidine unit and this should make thecyano-group much more susceptible to attack by a nucleo-HO OH HO OH HO OH phile.However, a methylthio group can also be dis-(71 a; R=NHMe,X=S ( 8 1 (9) a; R=Me placed by a n~cleophile.~ Treatment of (9a) with anb; R=NHEt,X=S b; R = CH2.CH : CHzexcess of crystalline hydroxylamine furnished the 4-methylthio-5-carboxamide oxime (6), identified on thebasis of the absence of i.r. absorption in the 2 250 cm-lregion, the U.V. spectrum and the MeS signal a t 6 ca. 2.5in the 1~ n.m.r. spectrum. Alkylation of (8) with allyl( 31a; = NMcz (l1a; R =H (2)b; R=Acverted into 4-amino-7-((3-~-ribofuranosyl)pyrro~o2,~-d- "'*"r;l -HO OH HO OH HO OHb; R = NHEt14) a; R=NHMe 15) (6 1C ; RzNH-OH, X=N*OHreflux temperature furnished the 4-hydroxyamino-com-Pound (4d) , identified by elemental analysis, U.V* and 'Hn.m*r.spectroscopy, and strong i*r* absorbance at 2 250bromide under similar conditions furnished 4-allylthio-7-( (3-~-ribofuranosyl)pyrrolo2,3-dpyrimidine-5-carbo-crn-l. However, when (5) was heated with an excess ofhydroxylamine in ethanol a t reflux temperature, reactionnitrile (gb).A study was initiated to determine the reactivity ofOccurred at both the cllloro-grouP and the 5-cYano-grouPto aff Ord 4-hYdroxYarnino-7~(~-D-ribofuranosY1)PY~010- the cyano-group of (5) under acidic conditions. Thenucleoside was added to dry ethanol and dry hydrogen 1~,3-dlpyrimidine-5-carboxamide oxime monohydrochlor- chloride was passed through the mixture.~h~ reaction ide (7c), which showed no i.r. cyano-absorption* To de- was monitored by t.lSc., which initial formation termine the sequence when an excess of hydroxylamineG. R. Revankar and L. B. Townsend, J, Hetevocyclic Chem., 5 R. J. Rousseau and L. B. Townsend, J. Ovg. Chem., 1968,53,1968, 5, 477. 2828, and references cited therein1250of the 6-cyano-4-ketone (la), followed by the form-ation of ethyl 3,4-dihydro4-oxo-7-( @-D-ribofuranosy1)-pyrr 010 2,3-4 pyrimidine-5- car boximidat e hydro-chloride. Therefore, under the acidic or basic con-ditions described above, the initial reaction is thedisplacement of the khloro-group, which is followedin some instances by a nucleophilic attack on the5-cyano-group. Our results corroborate the fact thatTABLE 1U.V.spectral data for certain 4,5-disubstituted ~ - ( P - D -ribofuranosy1)pyrrolo Z, 3-dJpyrimidinesPH 1 EtOH pH 11274279240-246293260276 'fit)276237264222264222306 w;)287248289260277330264(;;;I(;;;Iw;)';=;)266223224(290)2249-314-711.217.19- 215.613.714.317.215.312.623-016.221.212-411-28-29-311.213.414.412-220.04.813.514.53.321.03.629.129.013.031.06.3 2746.927.118.0 29021.8 29826.28.1l1.O 16.3 'z"27-612.8 28216.98.610.1 26413.3 27416.4 23013.7 29710.0 28110.6 26912.7 28312.1 26331-5 272br34.825.8 3226.2 2662309.321.0 17*6 'XX?17.6 2266.2 27021.5 2246-9 27429-2omas.8.417.218.710.716.916.37-618.817-28.91 i.918-813.713.710.69.713.112.09.619.16- 313-613.516.511.65.012.46.205-3 16 2.5 (288-302)229 19.6 230 19.613.8316 10.612-4 226 23.6 (22::)223 24.8Shoulders in parentheses.E x 10".the nature of the 4-substituent has a pronounced effecton the reactivity of the cyano-group towards nucleophilicaddition. To completely eliminate any effect of 4sub-stit uents we then synthesized 7-( p-~-ribofuranosyl)-pyrrolo2,3-dpyrimidine-5-carbonitrile (10) and studiedits chemical reactivity towards various nucleophiles.B. C. Hinshaw, J. F. Gerster, R. K. Robins, and L. B.Townsend, J. Heterocyclic Chem., 1969, 6, 216.3. F.Gerster, B. C . Hinshaw, R. K. Robins, and L. B.Townsend, J. Heterocyclic Chem., 1969, 6, 207.J.C.S. Perkin IDecNorination of Pchloro-7- ( p-~-ribofuranosyl)pyrro-102,34pyrimidine had been accomplished previouslyt o afford 7-deazanebularine. Treatment of 4-chloro-7-( ~-.~-nbofuranosyl)pyrrolo~2 , 3-41 pyrimidine-5-carbo-nitrile (5) under similar conditions (6 palladium-charcoal; hydrogen) effected a removal of the 4-chloro-group to give compound (10) without Concomitant re-duction of the 5-cyano-system VON 2 210 cm-l;6 8.9 (H-4) 6,' 9.2 and 8.2 (H-2 and -6), and 3.5-5(carbohydrate protons The reactivity of the cyano-group of (10) was then compared with that of the cyano-group of toyocamycin and the 4-oxo-nucleoside (la).It was presumed that substitution of a hydrogen atomfor the 4-amino-group of toyocamycin would have twomajor effects on the reactivity of the 5-cyano-group.First, the electron density at the carbon atom of thecyano-group in (lo) should be slightly decreased, whichshould facilitate nucleophilic attack at the cyano-group.Secondly a reaction of the cyano-group of toyocamycinis impeded in acidic solution presumably owing to pro-tonation of a nitrogen atom in the pyrimidine ring2Therefore, substitution of a hydrogen atom for theamino-group should decrease the electron density, with aconcomitant decrease in the ease of protonation of thepyrimidine unit.Removal of the oxo-group of (la)should, likewise, increase the reactivity of the cyano-group in (lo) under basic conditions.Treatment of (10) with dilute aqueous ammoniumhydroxide on a steam-bath for 3 h afforded a 75 yieldof 7-( p-~-ribofuranosyl)pyrrolo2,3-apyrimidine-5-carb-oxamide (1 1).Under similar conditions, toyocamycin0IIC-NH,(121 13) 114)R = p -D- ribofuranosylwas unchanged. Since earlier work had establishedthat under basic conditions the cyano-group of (la) wasless susceptible to nucleophilic attack than that oftoyocamycin, the reaction was not performed on (la).Treatment of (10) with crystalline hydroxylamine inL. B. Townsend in * Synthetic Procedures in Nucleic AcidChemistry, vol. 11, eds. W. W. Zorbach and R. S . Tipson, Inter-science, New York, ch. 7, 1973. * C. D. Hurd, Inorg. Synth., 1939,1, 871975 1251ethanol at reflux temperature for 0.5 h resulted in anaddition to the cyano-group to furnish the 5-carboxamideoxime (12) in 79 yield no vON; 6 9.4 (H-2), 8.9 (H-4),and 8.3 (H-6), 3-5-6 (carbohydrate protons), 9-65(exchangeable, NOH), and 5-9 (exchangeable, NH,).Under the same conditions, toyocamycin required 2 hand (la) required 4 h before the appearance of a product(as a precipitate). The thioamide analogue (13) wasobtained in 57 yield by treatment of (10) with metha-nolic sodium methoxide which had been saturated withhydrogen sulphide.The product showed no V(M, andU.V. absorbance above 310 nm. Milder conditions, usingpyridine, triethylamine, and hydrogen sulphide, pro-duced a compound whose U.V. and i.r. spectra wereidentical with those of (12).The above series of reactions indicate that the cyano-group of (10) is more susceptible to nucleophilic attackunder basic conditions than the cyano-groups of eithertoyocamycin or (la), which supports the assumptionthat the substitution of a hydrogen atom at C 4 for theamino-group of toyocamycin renders the cyano-carbonatom more electrophilic.Similarly, removal of the oxo-group of (la) precludes the formation of an anion underbasic conditions and thus eliminates the increased elec-tron density at the cyano-group and electrostatic repul-sion of the nucleophile due to anion formation.Treatment of (10) with hydrogen chloride in ethanolpresumably gave ethyl 7-( ~-~-ribofuranosyl)yyrrolo-2,3-qpyrimidine-5-carboximidate (14), but attempts toisolate this were unsuccessful.T.1.c. indicated that theimidate hydrochloride was formed, but was rapidly hy-drolysed or underwent a Pinner cleavage lo to form theamide (11). Attempts to prevent amide formation bylowering the reaction temperature resulted in no reaction(below 0"). The rapid formation ( 2 min) of a slow-moving (t.1.c.) u.v.-absorbing material followed by theappearance of a u.v.-absorbing substance with an Rpvalue equal to that of the amide (ll)* indicated that thecyano-group of (10) is more reactive under acidic condi-tions than that of toyocamycin. However, the imidate(14) is not as stable as the imidate of either toyocamycinor (la) .zCompounds (1 1)-( 13) show significant activity againstleukemia L-1210 in mice,lI with reduced toxicity in com-parison with the analogous nucleosides with an amino-group at C-4.These findings are in contrast to a previousreport l2 which indicated that the antitumour effects oftoyocamycin are intimately associated with the presenceof the amino-group at C-4 and the cyano-system at C-5.EXPERIMENTAL1.r. spectra were recorded for KBr discs with a BeckmanIR-5A spectrophotometer. M.p.s were determined with aThomas-Hoover capillary apparatus. lH N.m.r. spectrawere obtained with a Varian A-60 or 56/60 high resolutionspectrometer with sodium 2,2-dimethyl-2-silapentane-5-~~1-* The isolated product was identical (m.p., i.r. and U.V.spectra, Rp value) with amide (11). T.1.c. of the reaction solu-tion indicated the presence of a mixture of starting material (lo),intermediate (14), and final product (11) (after a prolongedreaction time of 6 h).phonate as internal standard and 2H,dimethyl sulphoxideas solvent.U.V. spectra were determined with a BeckmanDK-2 spectrophotometer. T.1.c. was performed on glassplates coated with a 0.25 mm thick layer of Silick 7GF anddeveloped by the ascending technique with PrOH-EtOAc-H,O (4 : 1 : 2 v/v/v) as solvent.3,4-Dihydr0-4-0~0- 7-( 2,3, B-tri-O-acetyl-a-D-ribofuralzosyl~yrvoZ02,3-dJ~~rimidine-B-carbonitrile (1 b)-To pyridine(40 ml) and acetic anhydride (20 ml) was added 3,4-dihydro-4-oxo-7-(~-~-ribofuranosyl)pyrro~o2,3-dpyrimidine-5-carbonitrile (la) (3.75 g). The mixture was kept a t 0" for36 h with occasional agitation.The pyridine and the ex-cess of acetic anhydride were then removed in vacuo on a hotwater-bath. The resulting syrup was dissolved in methylenechloride (100 ml) and washed with water (4 x 100 ml).The solution was dried (MgSO,), filtered, and evaporatedto dryness in vacuo. This furnished a foam (78). whichwas used without further purification.4-Chloro- 7- (2,3,5-tri-O-acetyl-13-~-ribo furanosyl)pyrrol'o-2,3-dpyrimidine-5-carbonitriZe (2) .-Compound ( lb) (5.0 g)was dissolved in phosphoryl chloride (1 5 ml) and heated atreflux temperature for 5 min. The hot solution was thenpoured onto an excess of ice with stirring while the tempera-ture was kept below 0". The resulting aqueous phase wilsextracted with dichloromethane ( 2 x 150 ml) and thecombined extracts were washed with cold water (100 mlportions) until the washings were neutral (ca.pH 7) to pHpaper, dried (MgSO,), filtered, and evaporated to dryness invacuo to yield a pale yellow syrup (4 g) (Found: C, 49.75;H, 4.3; N, 12.9. C,,H,,ClN,O, requires C, 49.5; H, 3.9;N, l2.8Y0).4-Chloro-7- (~-~-ribofuranosy~)pyrrolo2,3-d)~yrimid ine -5-carbonitrile @).-The triacetate (2) (4 g) was mixed withmethanol (100 ml) which had been previously saturated withammonia at -10". The mixture was kept at 5" with oc-casional agitation until all the syrup had dissolved, andafter 2.5 h the excess of ammonia and methanol was re-moved in vacuo at 35". The resulting syrup was dissolvedin boiling water (10 ml) and cooled at 5" for 12 h.The solidwhich formed was filtered off and air-dried to yield com-pound (5) (2.9 g, 68), m.p. 80-85" (Found: C, 46-15; H,3.8; N, 18.1. Cl,HllCIN,O, requires C, 46.4; H, 3.55; N,18.0yo)4-DimethyZamino-7- (P-D-ribo furan~syl)pyrrolo2,3-d -~yrimidine-5-carbonitrile (3a) ,-A solution containing coni-pound (5) (500 mg), ethanol (50 ml), and dimethylamine(2.5 ml) was heated at reflux temperature for 1 h. The ex-cess of dimethylamine and ethanol was removed in vacuo,the residue was dissolved in ethanol (20 ml), and the solutionwas evaporated to a syrup. The co-evaporation procedurewas repeated several times to remove the excess of dimethyl-amine. Trituration with a small amount of water furnisheda white solid, which was filtered off and recrystallised fromthe minimum of water to furnish compound (3a) (420 mg,81), m.p.170-172" (Found: C, 52.8; H, 5.7; N, 21.6.Cl,Hl,N,04 requires C, 52.8; H, 5.35; N, 22.0).4-Piperidino- 7- (P-D-rib0 furanosy1)pyrrolo 2,3-dpyrim-idine-5-carbonitrile (3b) .-Compound ( 5 ) (0- 1 g) dissolvedlo F. C. Schaefer, ' The Chemistry of the Cyano Group,' ed. 2.Rappoport, Interscience, New York, 1970, p. 264, and referencescited therein.Drug Research and Development Branch, Division of CancerTreatment, N.C.I., N.I.H., Bethesda, Maryland, U.S.A., un-published data.la M. Saneyoshi, R. Tokuzen, and F. Fukuoka, Gann, 1966, 56,2191252 J.C.S. Perkin Iin ethanol (12 ml) containing piperidine (0.5 ml) was heateda t reflux temperature for 1 h and then evaporated invacuo to a syrup.Ethanol was added and removed in vacuoseveral times to remove the excess of piperidine. The syrupwas then dissolved in water (10 ml), seeded* a t the cloudpoint, and cooled at 5" for 6 h. The crystals were filteredoff t o yield compound (3b) (70 mg, as), m.p. 201-203"(Found: C, 56.55; H, 5.9; N, 19.6. C,,H,,N,O, requires C,56-8; H, 5.89; N, 19*5y0).4Methylamino- 7- ( P-D-ribo furanosy1)pyrrolo 2,3-dpyrim-idine-5-curbonitriZe (4a) .-To ethanol (50 ml) containingmethylamine (5 ml) was added compound (5) (500 mg).The solution was heated a t reflux temperature for 1 h andthe excess of methylamine and ethanol was then removedin vacuo. The resulting solid was recrystallised fromwater to yield compound (4a) (330 mg, 67y0), m.p.138-139", which was dried for 2 h a t ca. 0.1 mmHg over Drieritefor analysis (Found: C, 51.4; H, 5.0; N, 23-1. C,,H,,N,O,requires C, 51.3; H, 4.95; N, 23.0).4-Ethylamino- 7- (P-D-ribo furanosyl)~yrrolo2,3-dpyrimi-dine (4b) .-To ethanol (25 ml) containing ethylamine (2.5ml) was added compound (5) (500 mg). The solution washeated a t reflux temperature for 1 h and then evaporated todryness in vacuo. The resulting syrup was triturated withethanol and then evaporated in vacuo; this procedure wasrepeated several times to remove the excess of ethylamine.The residue was recrystallized from the minimum of waterto yield compound (4b) (350 mg, 68), m.p. 180-184"(Found: C, 52.9; H, 5.25; N, 22.3.C14H17N504 requiresC, 52.8; H, 5.35; N, 22.0).4-Methoxy- 7- (P-~-ribofuranosyl)pyrrolo 2,3-dpyrimidine-5-carbonitrile (4c) .-To compound (5) (310 mg) in methanol(10 ml) was added solid sodium methoxide (270 mg). Thesolution was heated a t reflux temperature for 20 h and themethanol was removed under reduced pressure. The residuewas dissolved in water (10 ml) and the pH was adjusted to6 (~N-HC~). The white precipitate was filtered off anddissolved in boiling water (1 0 ml) . The solution was cooleda t 5" for 12 h to yield compound (4c) (150 mg, 48y0), m.p.190-192" (Found: C, 49.2; H, 5-0; N, 17.8. C,,H,,N,O,,0.5 H,O requires C, 49.5; H, 4-75; N, 17.8).pyrimidi.rze-5-carbonitrile (4) .-To compound( 5) (310 mg) inabsolute ethanol (10 ml) was added solid hydroxylamine 9(30 mg).The solution was heated at reflux temperature for6 h and then kept a t 0" for 12 h. The white crystals werefiltered off and recrystallized three times from water toyield compound (4d) (150 mg, 42), m.p. 261-263'(Found: C, 42-85; H, 4.9; N, 20.4. C,,H,,N,O,, 1.5 H20requires C, 43.1; H, 4.8; N, 20.0'70).pyrimidine-5-thiocarboxamide (7a) .-To pyridine (20 ml)containing triethylamine (0.5 ml) was added compound(4a) (150 mg). Hydrogen sulphide was passed through thisstirred solution for 5 h a t room temperature and the solventwas then removed in vacuo (hot water-bath). The residuewas co-evaporated with ethanol several times to remove theexcess of pyridine. The solid was then triturated with asmall amount of water, filtered off, recrystallized from water,and dried for 2 h under vacuum (P205) to yield compound(7a) (70 mg, 42), m.p.230" (Found: C , 43.8; H, 5.8; N,19-35. C,,H,,N,O,S requires C, 44.0; H, 5.35; N, 19.6).4-Hydroxyamino- 7- (P-D-ribofuranosyl)pyrrolo 2,3-d-4-Methylamino- 7- (P-D-ribo furanosyl)pyrrolo 2,3-d -* Seed crystals were obtained by crystallisation of the crudeproduct from ethyl acetate.4-Ethylamino- 7- (~-D-r~bofuranosyE)~yr~olo2,3-dpyrimi-dine-5-thiocarboxamide (7b) .-4-Ethylamino-7-( P-D-ribo-furanosyl)pyrrolo2,3-dpyrimidine (4b) (150 mg) was dis-solved in pyridine (25 ml) containing triethylamine (0.5 ml) .Hydrogen sulphide was passed through the solution withstirring for 5-45 h a t room temperature.The pyridine wasthen removed in vacuo and the resulting syrup was co-evaporated with ethanol several times. The solid wasrecrystallized from boiling water (10 ml), with enoughethanol added to effect dissolution, to yield compound (7b)(65 mg, 40), m.p. 217-218" (Found: C, 48.0; H, 5.9; N,19.9. C,,H,,N50,S requires C, 47.7; H, 5.45; N, 19-85y0)3,4-Dihydro-7-( ~-~-r~bofuranosyZ)-4-thioxo~yrrolo 2,3-dpyriunidine-5-carbonitriZe (8) .-Compound (5) (250 mg) wasdissolved in water (5 ml) containing thiourea (125 mg).Aqueous 25 formic acid (1 drop) was added and the solutionwas heated a t 80-85" for ca. 2 h while the pH was main-tained a t 5 by the addition of aqueous 25 ammoniumhydroxide. The reaction was complete when the pH re-mained constant.The water was removed in vacuo and theresidue was triturated with ethanol (10 ml). The solid wasfiltered off and recrystallized from water to yield compound(8) (120 mg, 50), m.p. 265-266" (decomp.) (Found: C,45.9; H, 3.95; N, 18.2. Cz,H,,SN,04,0~25H20 requiresC, 46.0; H, 4.05; N, 17.9).4-Methylthio- 7- (P-D-rib0 fura~tosyl)pyrroZo2,3-dpyrimi-dine-5-carbonitrile (9a) .-The thione (8) (0- 1 g) was dissolvedin water (5 ml), and aqueous 25 ammonium hydroxide(2 drops) and methyl iodide (40 mg) were added. The mix-ture was stirred at room temperature for 1 h, and the solidwas filtered off and recrystallized from boiling water (10 ml)(to which enough ethanol was added to effect dissolution)to yield compound (9a) (60 mg, 55), m.p.137-138"(Found: C, 47.6; H, 4-5; N, 16.9. C,,H1,SN40,,0~5H,0requires C, 47.7; H, 4.45; N, 17.1).4-A llylthio-7- (P-~-r~bofuranosyl)pyrrolo2,3-dpyrirnidine-5-carbonitrile (9b) .-To water ( 15 ml) containing concen-trated ammonium hydroxide (6 drops) was added com-pound (8) (300 mg) followed by ally1 bromide (0.5 ml). Thesolution was then stirred at room temperature for 2 h. Thesolid which had separated was filtered off, dried, and re-crystallized from boiling water (10 ml), with enough ethanoladded to effect dissolution, to yield compound (9b) (200 mg,63). The product was dried a t 110" in vacuo; m.p. 134-135" (Found: C, 51.65; H. 4.7; N, 16.1. C,,H,,N,O,Srequires C, 51.65; H, 4.6; N, 16.05).4-Methylthio- 7- (P-D-ribo furanosyl)~yrvolo 2,3-dpyrimidine5-carboxamide Oxime (6).-To compound (9a) (250 mg) inpropan-2-01 (25 ml) was added solid hydroxylamine (200mg).The solution was heated a t reflux temperature for 4h, then more hydroxylamine (100 mg) was added. Thesolution was then heated a t reflux temperature for an addi-tional 8 h. The propan-2-01 was removed in vucuo and theresidue was dissolved in the minimum of methanol. Theproduct slowly crystallized to yield compound (6) (90 mg,33), m.p. 195-196" (Found: C, 44.4; H, 4-85; N, 19-5.C,,N,,N,O,S requires C, 44.1; H, 4.85; N, 19.75y0).pyrimidine-5-carboxamide Oxime Monohydrochloride (7c) .-To compound (5) (310 mg) in absolute ethanol (10 ml) wasadded hydroxylamine (100 mg). The solution was heateda t reflux temperature for 30 min, then cooled to room tem-perature, and the solid was extracted with hot ethanol (25ml).The ethanol-insoluble material was filtered off andair-dried to yield compound (7c) (1 75 mg, 47) (Found : C,4-Hydroxyamino-7- (P-D-ribo furanosyl)pywoEo2,3-d197538.6; 13, 4-65; N, 22.0. C12H16N606 HC1 requires c , 38.3;H, 4.6; N, 22.35).7-( ~-~-R~bofuranosyl)~yrrolo2,3-d~yrimidine-5-carboni-tvile (10) .- 4-Chloro-7-( ~-~-ribofuranosyl)pyrolo2,3-d-pyrimidine-5-carbonitrile (5) (500 mg) was dissolved inethanol (50 ml), and 10 palladium-charcoal(300 mg) andsolid sodium hydrogen carbonate (500 mg) were added. Themixture was hydrogenated for 4 h a t room temperature and40 lb in-2, then filtered and evaporated. The resulting foamwas co-evaporated with ethanol (2 x 50 ml) to afford a hardyellow foam (320 mg, 68), m.p.175" (Found: C, 52-5; H,4.55; N, 20-7. C12Hl,N40, requires C, 52.15; H, 4.4; N,20*3y0).7- (P-D-RRibo furanosyl)pyrrolo 2, 3-dpyrimidine-5-carboxa-wide (1 I).-Compound (10) (0.5 g) concentrated ammoniumhydroxide (5 ml), and water (10 ml) were mixed and heatedon a steam-bath for 3 h. The solvents were removed invacuo and the residue was triturated with ethanol (20 ml) a troom temperature. The mixture was filtered and the solidwas recrystallized from ethanol (10 ml) with water addeddropwise to produce a clear solution. After cooling a t 5"for 12 h, the white crystalline product (11) was filtered offand dried under reduced pressure at 100"; yield 300 mg(yo), m.p.248-249" (Found: C, 49-0; H, 4.8; N, 19.15.C12H1,N,0, requires C, 49.0; H, 4.8; N, 19-05y0).7- (~-~-Rzbofuranosyl)~y~rolo2,3-d~yrimidine-5-curboxa-mide Oxime (12).-(10) (1.0 g), solid hydroxylamine (550mg), and ethanol (50 ml) were mixed and heated a t refluxtemperature. After 0.5 h a white precipitate had formedwhich was filtered off and washed with hot ethanol (50 ml).Recrystallization of the ethanol-insoluble material fromwater (20 ml) gave compound (12) (930 mg, 83), m.p.1253192-193' (Found: C, 43-95; H, 5-1; N, 21.2.H20 requires C, 44-05; H, 5-25; N, 21.4).7-(~-~-R~bofuranosyl)~yrrolo2,3-d~y~imidine-5-thiocar-boxamide (13) .-Method A . Compound (10) (750 mg) wasadded to methanolic sodium methoxide from sodium (100mg) in methanol (40 ml) and hydrogen sulphide was passedthrough the solution for 2 h. The flask was tightly stopperedand the mixture stirred a t room temperature for 12 h. Thepale yellow precipitate was filtered off and recrystallizedfrom the minimum of boiling methanol (to which water wasadded to the cloud point) to yield compound (13) (480 mg,57), m.p. 243-244" (Found: C, 45.4; H, 4.85; N, 17.65.Cl,H14N404S,0~5H,0 requires C, 45.3; H, 4.75; N, 17-55y0).Compound (10) (200 mg) was dissolved inpyridine (10 ml) containing triethylamine (0.2 ml). Hydro-gen sulphide was passed through the solution for 6 h at roomtemperature. The flask was tighly stoppered and themixture stirred a t room temperature euro;or an additional 18 h.The solvents were then removed under reduced pressure andthe residue was dissolved in the minimum of methanol andset aside a t 5" for 14 h. The pale orange powder whichformed was filtered off and air-dried to give a product (120mg, 55) identical (i.r. and U.V. spectra and m.p.) with (13)prepared by Method A.We thank the Division of Cancer Treatment, NationalInstitutes of Health, U.S. Public Health Service, for finan-cial support, Mr. S. Manning and his staff for the large-scalepreparation of starting material, and Mrs. S. Mason for u.v.,i.r., and 1H n.m.r. spectra. K. H. S. was NDEA Title IVrecipient 1970-1972, Department of Medicinal Chemistry.4/2164 Received, 18th October, 19741Cl2HI5N5O5,Method B