Syntheses, structural and conformational assignments ...

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Syntheses, structural and conformational assignments, and conversions of pyridine and triazolopyridine nucleosides' BRIANMAURICELYNCH^

AND

SURESHCHANDRA SHARMA~

Orgarlic Cl~etnistryLaboratory, Saittt Frat~cisXavier University, Antigot~isl~, Nova Scotia BOH ICO Received July 31, 1975 SHARMA. Can. J. Chem. 54, 1029 (1976). BRIANMAURICE LYNCHand SURFSHCHANDRA Regioselective and stereoselective routes to 2- and/or 4-substituted vic-triazolo(4,5-b)pyrid5-ones have been established, and series of 4- and 2-p-D-ribofuranosyl derivatives have been prepared as candidate substrates for, and potential inhibitors of, the enzymes of polynucleotide synthesis. Structural assignments were made by comparison of spectroscopic properties (prnr, uv) with those of appropriate model compounds, and on the bases of proton chemical shift and coupling constant patterns in the ribose moieties, it is proposed that 4-p-D-ribofuranosyl-victriazolo(4,5-b)pyrid-5-onesadopt conformations with 'high atlti' sugar-base torsional angles. A facile ribofuranose + ribopyranose conversion is observed with a 2-p-D-ribofuranosyl-victriazolo(4,5-b)pyrid-5-one. BRIANMAURICE LYNCHet SURFSHCHANDRA SHARMA. Can. J. Chem. 54, 1029 (1976). On a etabli des methodes rCgioselectives et sterCosClectives pour conduire aux vic-triazolo(4,5-b) pyridones-5 substitukes en positions 2 et/ou 4; on a prepare des series de derives de p-D-ribofurannosyles substituks en positions 2 et 4 comme substrats possibles pour, et comme inhibiteur potentiel de la synthkse, des enzymes responsables de la synthbe de polynucliotides. On a fait les attributions de structure par comparaison des propriCtCs spectroscopiques (rmp et uv) avec celles de composCs modkles appropries; sur la base des dkplacements chimiques et des patrons des constantes de couplage dans la portion ribose on propose que la p-D-ribofurannosyl4 vic-triazolo(4,5-b) pyridones-5 adopte une conformation avec des angles de torsion sucre-base 'Clevis en arrti'. Avec la b-D-ribofurannosyle-2 vic-triazolo(4,5-b) pyridone-5 on observe une conversion facile du ribofurannose en ribopyrannose. [Traduit par le journal]

Introduction Certain pyridine (3-deazapyrimidine) nucleosides exhibit antibacterial and antileukemic activities (l,2), and bicyclic unnatural nucleoside species with the sugar moiety in the six-membered ring (including nucleosides of oxazolo(4,5-b)pyrimidines (3), pyrrolo(2,3-r1)pyrimidines (4), thiazoIo(5,4-d)pyrimidines (5), pyrido(2,3-d)pyrimidines (6), and quinazolines (7)) have shown significant biochemical and chemotherapeutic activities. The present work forms part of a program of exploration of stereospecific and regioselective syntheses of unnatural nucleosides, and is concerned with each of the above general classes, where appropriately substituted pyridines or pyridine nucleosides are used as precursors of 'Presented in part at the 54th Canadian Chemical Conference of the Chemical Institute of Canada, Halifax, Nova Scotia, June, 1971. 2Author to whom requests for reprints should be addressed. 3Professional Research Associate.

4-substituted vic-triazolo(4,5-b)pyridines, and the species obtained are subjected to further alkylations and/or ribosylations. The primary objective of this synthetic program is t o obtain a set of positionally isomeric nucleosides with markedly


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CAN. J. CHEM. VOL. 54, 1976

different geometrical and steric constraints on preferred sugar-base torsional angles, providing test compounds for the postulated restriction of the enzymes of polynucleotide synthesis to nucleoside phosphate substrates possessing anti conformations (8-1 1).

R-N

b

Results and Discussion

(a) Syntheses and Conversions The 2-pyridone nucleosides 16,2b, and 36 were obtained by treatment of the trimethylsilyl derivatives of the precursor species l a , 2a, and 3a with tetra-0-acetyl-P-D-ribofuranose (12) in refluxing 1,2-dichloroethane in the presence of anhydrous tin(1V) chloride (13, cf. 14-16). followed by deacetylation with ammonia-saturated methanol. The tri-0-benzoylribofuranose species I d was similarly obtained from 1-0acetyl-2,3,5-tri-0-benzoyl-P-D-ribofuranose (17), and 16 was accessible from the reaction of 1bromo-2,3,5-tri-0-acetylribofuranose(18) with the trimethylsilyl derivative of l a , without catalysis by the tin(1V) species. The compounds la-lf were converted into the corresponding 4-substituted vic-triazolo(4,5-6)pyrid-5-ones 4a-4f, using the successive substitution and cyclization effected by azide ion in aprotic dipolar media (a route established by Fox and co-workers (19)). The intermediate additioncyclization product 5 in the conversion 16 + 4b may be isolated from the reaction mixture (see Experimental), and yields 46 on acid treatment. The yields of 46 obtained via deblocking of the species 4c and 4d, using the protected nucleosides

l c and Id, were significantly better than for the direct conversion of 16 into 46. Further treatment of the trimethylsilyl derivatives of several compounds of general structure 4 with tetra-0-acetyl-p-D-ribofuranose under tin(1V) catalysis efficiently introduces the triacetylribofuranose moiety selectively into the 2-position of the vic-triazolo(4,5-6)pyridone nucleus, yielding the compounds 6c-6f. Deblock-

ing of 6c provided the hygroscopic bis-riboside 76, and deblocking of 6e provided 7e. Remarkably, attempted reacetylation of 7e resulted in a ribofuranosyl + ribopyranosyl conversion, yielding the species 8.

To provide model reference compounds, the parent vic-triazolo(4,5-6)pyrid-5-one 4a was dimethylated in basic media, and the 4-methyl conlpound 4e similarly methylated, yielding a mixture of three dimethylated species in the ratio (as estimated from integration of the characteristic triazole N-methyl proton signals) 1:0.27:0.02, identified (see section b below) respectively as the 2,4-,1,4-, and 3,4-species 10,11, and 12; 10 and 11 were separable by sublimation under reduced pressure. (6) Structure Assignments If 1-substituted-5-nitro-2-pyridones are employed as starting materials, the cyclization route assures definition of the 4-substituted vic-


LYNCH A N D SHARMA

-

1031

N-methyl signal (6 4.22), requiring its formulation as the 1,4-dimethyl species. The predominant methylation product from (ii) 4a and 4e, species 10, mp 134 " C , showed no la-lj 4a-4f Overhauser enhancement-of the pyridone N(i) methyl signal (6 3.49) when the triazole N-methyl 4c-4e 6c-6e signal (6 4.28) was irradiated, thus ruling out the (i), (iii) 3,4-dimethyl species 12 and requiring assignment 4f 71 as the 2,4-dimethyl compound. The third isomer (iii) 6c P 7b from the n~ethylation,formed in smallest pro(iii) (iv) portion, is then assigned as the 3,4-dimethyl 6e - 7 e d 8 compound 12, and the low field positions of each of the two N-methyl signals in this compound (by comparison with the other isomers) may be attributed to steric compression or steric polarization influences. FIG. 1. Flow sheet of reactions and conversions: With the structures 10 and 11 as reference ( i ) treatment with 1,2,3,5-tetra-0-acetyl-8-D-ribofuranose in C2H4C12with SnCI4; (ii) annelation with azide ion in points, the presence of a triazole N-methyl signal aprotic dipolar solvent; (iii) deblocking with NH3at 6 4.27 defines the structure of the methylation C H 3 0 H or NaOCH3-CH30H; (iv) acetylation with product of compound 4b as the 2-methyl-4-P-DAc2O-pyridine; (v) methylation with CH31-Na2C03. ribofuranosyl compound 9. Further, the occurtriazolo(4,5-b)pyrid-5-one structure, but further rence of the pyridone N-methyl signals in the alkylations (including ribosylations) could occur 6 3.47-3.53 region in the triacetylribosyl coma t each position in the triazole ring, and un- pounds and the ribosyl derivative obtained from equivocal identification and separation of related 4e (compounds 6e, 8, and 7e), rather than in the species has offered considerable difficulties (cf. 6 3.61 region, suggests the 2,4-substitution uattern. Further nuclear Overhauser effect ex20-23). periments supported the suggestion that introThe structures of the compounds cited in duction of the blocked ribosyl species in the section a were established using pmr spectroscopy tin(1V) catalysed conversions of the compounds and electronic spectroscopy, with reference to the occurs selectively at the 2-position. Tests for enpatterns shown by the model compounds 10 and hancement of the H-1' signal by irradiation of 11 (see Tables 1 and 2). The structure assignment the pyridone 7-proton, or by irradiation of the to compound 11, inp 201-203 "C, was made protons of the 4-substituent, gave null results for using the nuclear Overhauser effect (24, 25). the compounds 6c-6f. This compound showed an 11% increase in Since some abnormal relaxation effect could signal intensity for the low field pyridone 7cast some doubt on the null results from the proton (6 7.97) on irradiation of the triazole nOe experiments, we also made comparisons of the electronic spectra of the compounds 10 and 11 with the various ribosylated derivatives (see Table 2). Conlpound 10 (the 2,4-dimethyl compound) shows two discrete intense maxima above 300nm; compound 11 shows a single peak in this region. All the compounds obtained by introduction of a methyl or blocked ribosyl species into a 4-substituted vic-triazolo(4,5-b)pyrid-5-one show spectral patterns resembling 10, but not 11, and are confirmed as 2-substituted species. The slight but significant bathochromic and hyperchromic effects in the 2,4- vs. 1,4species are consistent with previous findings (26-28) that 'extended' N-substituted species (of


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TABLE1. Proton magnetic resonance spectra of vic-triazolo(4,5-h)pyrid-5-ones* Coupling constants (Hz)

Chemical shifts for protons (ppm) Species

1'

7-

6-

Others

Jlr7'

6c (in CDC1,) 6e

Sf

7b (in D 2 0 ) 7e 7f

8 9 10 11 12

'Unless otherwise stated, all spectra are for ca. 4y0w /v solutions in DMSO-do, and all Ja; values arc 9.4 ? 0.1 Hz.

type 10) show more intense and longer wavelength maxima than isomers with an N-substituent adjacent t o an azine ring. In assignments of anomeric configurations to couplings unnatural ribofuranosides, small J1121 (less than 4 Hz) may be regarded .as strongly TABLE2. Electronic absorption spectra of vic-triazolo(4,5-b)pyrid5-ones (in methanol) Species

Amax

(nm)

log

E

indicative of frans-hydrogens (29), and thus of a 0-configuration. The bicyclic species 46, 5 and 9 show H-I' couplings much greater than this, but since these conlpounds derive from the compound 16 (with J1,2, h. 0 and thus unambiguously p), they are almost certainly p-species. There is the unlikely possibility that stereospecific anomerization occurs under the influence of the azide nucleophile, and to eliminate this, we converted 46 into its isopropylidene derivative. These species commonly show decreased J 1 r 2 r values as compared with the parent ribofuranoside, and it has been shown (30-32) that the chemical shift difference between the methyl groups of such derivatives may be used t o confirm configurations (a difference > 0.18 ppm is diagnostic of a ir) configuration (31)). The isopropylidene derivative of 46 showed methyl signals a t 6 1.35 and 1.67, with JIc2, = 3.50 Hz, and is clearly 0. For the series of peracetylated ribosides (4c, 6e, 61) J112, is less than in the deblocked species (46, 7e, 7j3 (see Table 1); yet in the course of attempted reacetylation of the deblocked riboside 6e using acetic anhydride- pyridine a t room temperature, an isomeric product distinct from (7.3 HZ). 7e was obtained, showing a large From the close correspondence of the comparable 13C nmr ribose carbon signals in the J 1 1 2 1


LYNCH

-

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AND SHARMA

TABLE3. 13C nmr spectra of 4-methyl-2-(p-~-2,3,5-tri-O-acetylribofuranosyI)-victriazolo(4,5-h)pyrid-5-one(6e), 4-methyl-2-(~-~-2,3,4-tri-O-acetylribopyrdnosyl)vie-triazolo(4,5-6)pyrid-5-one(8) and 1,2,3,5-tetraacetyl-p-~ribofuranose and 1,2,3,4-tetraacetyl-pa-ribopyranose

I3Cchemical shifts (ppm) I3Cassignment

6r

Acetyl carbonyls

170.0 169.6 169.4

Pyridine ring C-2 C-6 C-4 C-5 C-3 Ribose ring C-1' C-4'

161.3 148.5 130.9 129.2 124.6 93.6 80.1 73.5 70.6 62.8 29.3 20.3

C-3' C-2' C-5' N-Methyl Acetyl methyls

Tetraacetylribofuranose

170.0 169.3 169.1 168.6

98.2 79.4 74.2 70.6 63.6 20.9 20.33 20.55 20.31

compound 7e and its isomeric deblocking -+ reacetylation product to those of tetraacetylribofuranose and tetraacetylribopyranose models (see Table 3). ,. it is clearlv evident that conversion into the pyranose speci& 8 has occurred (assignments of nuclei in Table 3 are based upon the 13C spectra of the parent sugars (33) and some nucleosides (34), and standard ranges for pyridine ring atoms and for acetyl carbonyl and methyl groups (35)). The high value of J 1 r Z t (7.3 Hz) in 8 establishes that the configuration of the ribopyranose moiety remains P, since apyranose nucleoside species are characterized by small values (ca. 2 Hz, cf. Montgomery and Thomas (36)). Although it is well known (37) that the pyranose form of ribose species is favored thermodynamically, and there are precedents for furanose -+ pyranose conversions-with azapurine nucleosides (36), the ease of conversion in the present example is noteworthy, and suggests that careful -continued monitoring of isomeric structures in nucleoside conversions is appropriate. Finally, the P-ribofuranosyl configurations are tentatively assigned to the 2-substituted derivavalues tives 6c-6f, 7b, 7e, and 7f, since the for the peracetylated precursors 6 (from which the nucleosides~areobtained by deblocking), are J1l2t

8

169.85 169.2 168.6 161.2 148.2 130.8 129.2 124.7 86.4 67.6 67.0 65.6 63 .O 29.2 20.4 20.1

Tetraacetylribopyranose

169.55 169.4 169.2 168.4

90.9 67.3 66.3 66.2 62.6 20.720.65 20.620.55

uniformly less than 4 Hz (Table 1, cj'. Stevens and Fletcher (29)). (c) Srrggested Conforn7ational Prejerences: Sugar-Base Torsioizal Relationships The interpretation given below relies largely upon the definitive discussions by Altona and Sundaralingam (38, 39). The unusual structural features in the nucleoside 4b, where the sugarbase link is sited between an amide carbonyl and the conjoined triazole ring, might be expected to impose conformational restraints, which should be evident in differences in the pmr spectra of the ribose protons in 4b as compared with species possessing fewer constraints (cf ref. 8). Changes by comparison with 'normal' ribosides might include: (i) a change in the ribose conformation towards the S-conformation (C(2')-enrlo, C(3')-exo, 2T3 (38, 39)), since for this conformation, the base moiety adopts a quasiequatorial site, so that bulky groups in the base then interact least with the ribose 3'-, 4'-, and 5'-substituents (40); this should be evident in high values for the coupling constant Jlt2'; (ii) increases in the coupling constant J2'3ffrom values characteristic of anti nucleosides (4.8-5.5 Hz) (39) towards the range 6.G6.4 Hz, as observed for the analogously substituted nucleo-

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TABLE4. The pmr spectra of various ribosides related to 4-p-~-ribofuranosyl-vic-triazolo(4,5-b)pyrid-5-one* Coupling constants (Hz)

Chemlcal shifts (ppm) Species

4b lb 5 Uridine Inosine Adenosine 6-Azauridine 8-Azaxanthine, 3-riboside (36) 3-Ribosyladenine (45) 3-Ribosylhypoxanthine (45)

H-1 '

2'

3'

4'

5',5"

6.38 5.95 6.55 5.80 5.85 5.90 5.91 6.12 5.95 5.98

4.80 4.03 5.00 4.05 4.52 4.65 4.25

4.23

3.90

3.67 3.77

4.00 4.17 4.13 4.03

3.85 3.95 4.00 3.77

3.63 3.60 3.60 3.50

J182,

6.50

ZO 7.50 4.50 5.50 6.00 3.50 7.00 7.00 6.00

J2'3,

6.00 ~ 5 . 0 6.00 5 .OO 4.80 4.00

2,4-Dioxo-1-0-D-ribofuranosylpyrido(2,3-qpyrimidine (6)

6.56

3.50

1-B-D-Ribofuranosylquinazoline2,4-dione (8)t

6.55

4.93

4.54

4.22

4.10

A l l original spectra are for 5 % w / v solutions in DMSO-(1'. Missing entries indicate that proton signals were not readily resolved (for current work), or that the data were not pl.esentcd (literature data). tValues with rcspect to external TMS capillary.

sides orotidine (41) and 0-cyanuric acid riboside (42); (iii) downfield shifts in the H-1' and H-2' resonances (as compared with the monocyclic l b , assumed to adopt an anti conformation), associated with deshielding of these nuclei by the carbonyl and triazole functions. Table 4, which includes conlparisons of 4b with several related ribosides, shows that each of these proposed features appears in the pmr spectra of 4b (and of the intermediate 5): the coupling constants J l y and J2'31have high values; H-1' is deshielded by 0.43 ppm, and H-2' by 0.77 ppm as compared with lb. Dreiding molecular models for 'highartti' (intermediate arzti-syn) (43) conformations for 4b (see Fig. 2) indicate that both H-1' and H-2' will be under the deshielding influences of either the carbonyl group or the unshared pair of the nitrogen at position 3. We suggest that each of the structures A and B of Fig. 2 will be energy minima anlong the torsional range for 4b.

(1') A

B

FIG 2. Hydrogen and oxygen atoms other than those of the ribose skeleton are omitted for clarity.

(d) Prognosis for Future Work We are now engaged in syntheses of the nucleoside phosphates of the newly available ribosyl species, and plan to evaluatethese as substrates for polynucleotide phosphorylases (8-1 1). The synthesized ribosides are also being supplied t o the Universitv of Alberta Cancer Research Unit for evaluation as inhibitors of the enzymes of purine synthesis. We hope to extend our nmr studies, using 13C-H vicinal couplings t o verify the proposed sugar-base torsional relationships (cf. ref. 44).

Experimental General Melting points were determined using a Fisher-Johns apparatus or a Kofler Heizbank. Most of the proton magnetic resonance spectra were recorded with a Varian A-60D instrument using DMSO-d6 as solvent, while the nuclear Overhauser effect (nOe) experiments were made using a Varian HA-100. The '"2 magnetic resonance spectra were obtained for deuteriochloroform solutions using a Varian XL-100 spectrometer in the Fourier transform mode with full proton decoupling. All chemical shifts (proton and "C) are expressed in parts per million downfield from internal tetramethylsilane. Infrared spectra (potassium chloride disks) were measured o n a Beckman Acculab 4 instrument, and electronic absorption spectra with a Beckman Acta 111 spectrophotometer. Column chromatographic separations used Fluka Type 507C neutral alumina, Brockmann activity 1. Specimens for elemental analyses were dried at 65 "C/0.2 torr for at least 6 h and were analysed using a Hewlett-Packard


LYNCH AND SHARMA

Model 185 CHN Analyser. All extracts were dried over anhydrous sodium sulfate and evaporations were effected below 35 "C under reduced pressure. Known compounds referred to in the tables and in details of experiments were commercial materials, whose physical properties accorded with Literature values.

1035

The pmr spectra: 6 6.00 (d, lH, J = 2.0 Hz, H-l'), 6.50 (t, IH, J = 7.0Hz, H-5), 8.20 (dd, lH, J = 7.0 and 2.3 Hz, H-4), 8.48 (dd, l H , J = 7.0 and 2.3 Hz, H-6). (d) 3-Cyatio-I-p-~-ribofiirc~110.~~~l-2-pyrir/0tre, 3b 3-Cyano-2-pyridone (0.70 g), mp 222-225 OC, was ribosylated following the procedure of method i above, yielding 36 (0.70 g, 48';/L), mp 22G222 'C, after crystallization from ethanol. At~al.calcd. for C1lHl2N205: C 52.38, H 4.80, N 11.11; found: C52.69, H 4.81, N 11.10. The pmr spectra: 6 6.08 (d, l H , J = 2.0 Hz, H-l'), 6.54 (t, l H , J = 7.5 Hz, H-5), 8.49 (dd, l H , J = 7.5 and 2.5 Hz, H-6 or H-4), 8.64 (dd, l H , J = 7.5 and 2.5 Hz, H-4 or H-6).

2-Pyridotie Nucleosides (a) S-Nitro-l-~-~-ribofi11'a110syl-2-pyridotie, Ib Merilod i - 5-Nitro-2-pyridone (3.0 g) in hexamethyldisilazane (40 ml) was heated under reflux with a catalytic amount (IOmg) of ammonium sulfate for 4 h, with precautions for exclusion of moisture. Excess solvent was removed under reduced pressure and the residue, without further purification, was dissolved in 1,2-dichloroethane Atrtielatiotz Reactiotrs Yielditlg Triazolopyridotres (100 ml) and 1,2,3,5-tetra-0-acetyl-m-ribofuranose (6.25 4-p-~-Ribofi~rat1os);I-vic-rria~olo(4,S-b)p)~rid-5-o11e, 4b g) and tin(1V) chloride (1.0 ml) were added. The mixture To the nucleoside lb (8.15 g) in dimethyl sulfoxide (50 was heated under reflux for 8 h and allowed to stand at ml) was added sodium azide (2.40 g) and the mixture room temperature for a further 12 h. 1,2-Dichloroethane was heated at 115-1 17 "C for 24 1 (stirring). The cooled (50 ml) was added to the reaction mixture, which was solution was diluted with chloroform (200 ml) and the washed successively with aqueous sodium carbonate and resulting semisolid was collected by decantation, dissolved with water, and the organic phase was dried. Concentra- in the minimum quantity of methanol, and applied to a tion under reduced pressure yielded an oil whose pmr neutral alumina column (100 g, moistened with chlorospectrum was consistent with formulation as the tri-0- form). Elution with methanol followed by evaporation acetyl species lc. The oil was treated at 0 "C for 4 days under reduced pressure yielded the intermediate 5 (1.63 g), with methanol (225 ml) presaturated with ammonia at mp 254-256 "C (shtinks at 235 'C) after crystallization 0 ° C . Concentration of the solution under reduced from water. This material showed no azide absorption in pressure, followed by crystallization from water, provided the 2000-2500 cm-1 region; pmr spectra, see Table 1. 5-nitro-1-B-D-ribofuranosyl-2-nitropyridone lb (4.83 g, Crystallization from 1 M hydrochloric acid yielded 4b, go%), mp 225 "C. Atral. caldd. for CIOHIZNZ07: C 44.12, mp 263-265 "C (dec.). Atral. calcd. for CloH~~N405: C H 4.44, N 10.29; found: C43.70, H 4.50, N 10.30. The 44.78, H 4.51, N 20.89; found: C 44.83, H 4.56, N 20.63. pmr spectra: 8 5.95 (s, l H , H-1'), 6.52 (d, l H , J = 9.5 Hz, For pmr spectra, see Table 1. H-3),8.15(dd, l H , J = 9.5and3.3 Hz,H-4),9.66(d, IH, 4-~-~-(2,3,5-Tri-0-~~ce!yirib~/rirat1osyl)-vic-triazoloJ = 3.3 HZ, H-6). (4,5-b)pyrir/-5-ow, 4c Merilorl ii - 5-Nitro-2-pyridone (1.50 g) was converted T o the nucleoside lc (13.50 g) in N,N-dimethylforminto its trimethylsilyl derivative as above, and was treated amide (50 ml) was added sodium azide (5.20 g), and the with l-brom0-2,3,5-tri-O-acetylribofura11ose (18) (3.25 g) mixture was heated at 110 "C for 24 h, and concentrated in 1,2-dichloroethane (100 ml). The mixture was heated under reduced pressure (0.8 torr). The residue was exunder reflux for 6 h and left at room temperature over- tracted with chloroform ( 3 X 100 ml), washed with 1 M night. Deacetylation as in method i and crystallization hydrochloric acid and with water, and the organic extract from water provided 1b (2.1 1 g, 70y0) mp and mixture mp was dried and the solvent removed. The residual oil (8.70 225 "C. g) was dissolved in ethyl ether (150ml); slow evaporation (b) 5-Nilro-I-~-~-(2,3,5-1~i-O-bet1zoyIribo/I1rat~o~yl)of the ether yielded 4c as light yellow crystals (5.37 g, 2-pyridotre,Id 407;), mp 223-224 "C. Atlrrl. calcd. for Cl6H18N408: C The trimethylsilyl derivative, prepared as above from 48.73, H 4.60, N 14.21; found: C48.87, H 4.36, N 14.49. 5-nitro-2-pyridone (2.80 g) was treated with l-acetyl- For pmr spectra, see Table 1. Deblocking with ammonia 2,3,5-tri-0-benzoyl-8-n-ribofuranose (17) (9.50 g) in 1,2- saturated methanol alrorded the nucleoside 4b quantitadichloroethane (100 ml) and the mixture was heated under tively. reflux for 8 h in the presence of tin(1V) chloride (1.0 ml). 4-8-D-(2,3,5Tri-0-betr~oylribo/rir~~t~osyl)-vic-lriazoloAfter working up as in method i above, andcrystallization (4,5-b)p)lrid-5-orre, 4d from ethanol, the product Id was obtained (8.37 g, 72y0), The nucleoside derivative Id (5.90 g) in N,N-dimethylmp 178-180 "C. Atlal. calcd. for C 3 1 H ~ 4 N ~ O Cl63.69, ~: formamide (50 ml) was heated with sodium azide (2.40 g) H 4.14, N 4.79; found: C 64.06, H 4.20, N 4.43. The at 88-90 "C (stirring) for 24 h. The solvent was removed pmr spectra: a 6.28 (s, l H , H-1'), 6.57 (d, I H , J = 9.5 under reduced pressure (0.5 torr) and the residue was Hz, H-3), 8.17 (dd, l H , J = 9.5 and 2.9Hz, H-4), 9.17 neutralized with 2 M hydrochloric acid. The product was (d, l H , J = 2.9 Hz, H-6). Id afforded the deblocked isolated by extraction with chloroform (3 X 75 ml). nucleoside lb in quantitative yield on treatment with Evaporation of the extract followed by crystallization ammonia saturated methanol. from ethyl ether yielded 4r/(5.49 g, 93';';), mp 157-159 "C. (c) 3-Nitro-I-~-~-ribo/Iiranos)~l-2-pyridotre, 2b Atlol. calcd. for C3LH24N408:C 64.13, H 4.17, N 9.65; 3-Nitro-2-pyridone 2a (1.50 g), on ribosylation follow- found: C 64.34, H 4.41, N 9.29. For pmr spectra, see ing method i above, yielded the product 2b (1.50 g, Sly0), Table 1. Deblocking with 0.5 M methanolic sodium mp 225-228 "C. Atzal. found: C 44.30, H 4.38, N 10.38. methoxide afforded 4b quantitatively.


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CAN. J. CHEM. VOL. 54. 1976

crystallized from methanol, yielding 0.71 g of material, mp 135-137 "C. The compound was too hygroscopic for satisfactory elemental analysis, but the pmr spectra support the assigned structure (see Table 1). 4- ~ell1)~l-2-p-~-ribo~~rc1~1o.r)~/-vic-'triazolo(4,5-b)~~r 5-otre, 7e The 4-methyl-2-triacetylribofuranose derivative 6e (2.50 g) was treated with freshly prepared sodium methoxide in methanol (from 0.50 g sodium in methanol (50 ml)) a t 21 "C for 20 h. The solution was neutralized by passage through Amberlite resin IRC-5O(H), and concentration of 2,4-ilis(p-~-2,3,~-tri-O-acet~~ribojrr~otrosy~)-vic-trio~o/othe solution gave the deacetylated nucleoside 7e, which (4,5-b)p)~rici-5-o1le,6c was crystallized from 2-propanol to give needles (1.48 g, The peracetylated triazolopyridone nucleoside 4c (0.80 8659, mp 135-137 "C. Atrctl. calcd. for CllHI~N405:C g) was heated under reflux with hexamethyldisilazane 46.81, H 5.00, N 19.85; found: C 47.08, H 4.83, N 19.66. m for For pmr spectra, see Table 1. (15 ml) and a catalytic amount of a m m o l l i ~ ~sulfate 3 h, with precautions for exclusion of moisture. After 4-Bet1zyI-2-p-~-ribofrrrctt1os)~~-vic-~rin:olo(4,5-b)pyrid-5removal of the excess of hexametl1yldisilazane, the residue one, 7f was dissolved in 1,2-dicl~loroetllane(50 ml) and reacted 4-Benzyl-vie-triazolo(4,5-b)pyrid-5-one 4f (3.45 g) was (0.68 g) and converted into the trimethylsilyl derivative by treatment with 1,2,3,5-tetra-0-acetyl-p-D-ribofuranose tin(1V) chloride (0.5 ml) by heating under reflux for 8 h. with excess of hexamethyldisilazane, and dissolved in Chloroform (50 ml) was added and the organic layer was 1,2-dichloroethane (I00 ml) when 1,2,3,5-tetra-0-acetylwith water, saturated aqueous sodium p-D-ribofuranose (4.52 g) and tin(IV) chloride (0.7 ml) shaken s~~ccessively hydrogen carbonate, and water. After drying and con- were added. The reaction mixture was heated under centration, followed by crystallization from methanol, reflux for 8 h and left at 21 "C for 16 h. After the usual the product 6c was obtained, mp 63-65 "C (1.40 g, 85%). isolation procedure, a viscous oil (6.70 g, 90% based on Atrnl. calcd. for C27H32N4015: C 49.70, H 4.94, N 8.58; the assumption that the triacetylribofuranose moiety had found: C 50.03, H 5.26, N 8.25. For pmr spectra, see been introduced) was obtained. The oil (5.0 g) was disTable 1. solved in freshly prepared sodium methoxide in methanol 2-p-~-2,3,5-Tri-O-acet~/ribojrrntros)~~-4-p-~-2,3,5-tri-0(0.8 g sodium in methanol (701111)) and left at room be~rzoylriboflrrrttro.rj1-vie-t rictzolo(4,5-b)pyt~i(I-5-o,re,6d temperature for 16 11. The solution was neutralized by The tribenzoyl derivative 4cl(2.50 g) was heated under passage through Amberlite resin IRC-50(H), and the reflux for 18 h in hexamethyldisilazane (35 ml) as for 6c product isolated on concentration was crystallized from above. Excess solvent was removed under reduced methanol - ethyl ether, yielding needles of 7f (2.88 g, 78% pressure, and the residue was dissolved in l,2-dichloro- based on the 5.0 g portion), mp 191-193 "C. Arlal. calcd. ethane (80 ml); 1,2,3,5-tetra-0-acetyl-p-D-ribofuranosefor C17HISN405:C56.98, H 5.06, N 15.63; found: C (1.34 g) was added, together with tin(1V) chloride (0.5 ml), 56.75, H 5.00, N 15.69. For pmr spectra, see Table 1. and the mixture was heated under reflux for 8 h. Work-up 4- Met/1yl-2-p-~-(2,3,4-~t~i-0-ace~ylribop~rnt~osyl)-vicas for 6c gave crude material, which was purified by trir~zolo(4,5-b)p~rid-5-o11e, 8 crystallization from ethanol, yielding 1.0 g (28%) of 6d, T o 4-methyl-2-p-~-ribofuranosyl-vic-triazolo(4,5-b)mp 66-68 "C. Atlcrl. calcd. for C-12H3SN4015:C60.14, pyrid-5-one 7e (0.22 g) in dry pyridine (10 ml) was added H 4.57, N 6.68; found: C 60.48, H 4.93, N 6.54. acetic anhydride (1.0 g) and the reaction mixture was 4-Met/1yl-2-j3-~-2,3,5-tri-O-ncet)~~t.iboflrt~cttrosy~-vicleft at 21 "C for 64 h. The solution was concentrated tricrzolo(4,5-b)p)~ricl-5-otre,6e under reduced pressure (4 torr), and the solid thus The trimethylsilyl derivative prepared from 4-methyl- obtained was treated three times with ethanol (15 ml vie-triazolo(4,5-b)pyrid-5-one4e (19) (1.50 g) by treat- portions) with successive evaporation under reduced ment with excess of hexarnethyldisilazane, was reacted pressure, and finally crystallized from ethanol, providing (3.05 g) and the triacetylribopyranose species 8 (0.29 g, 917,), mp with 1,2,3,5-tetra-0-acetyl-p-D-ribofuranose tin(1V) chloride (0.5 g) in 1,2-dichloroethane (50 ml) 185-186 "C. Atrul. found: C 50.25, H 5.25, N 13.81. For under reflux for 6 h, and left at room temperature for pmr spectra, see Table 1 ; 13C nmr spectra, see Table 3. 18 h. The product was isolated after removal of inorganic materials in the usual manner, and crystallized from Metl~ylatiot~s of Triazolopjriciotre Species petroleum, bp 60-65 "C, as colorless needles, mp 52((I) Methylation of vie-triazolo(4,5-b)pyrid-5-one,4a. 53 "C. Atrctl. calcd. for C17H20N40X:C 50.00, H 4.94, T o the above-named compound 4n (19) (0.50g) in N 13.72; found: C 50.04, H 5.02, N 13.59. For pmr methanol (100 ml) was added methyl iodide (0.5 ml) and spectra, see Table 1 ; 13C nmr spectra, see Table 3. potassium carbonate (0.50g) and the mixture was set 2,4-ilis-p-~-ribo~rrcttros)~/-vic-tt~iazolo(4,5-b)pyri~I- aside at 21 "C for 16 h. The solution was concentrated and 5-one, 7b the residue was extracted into chloroform (3 X 50ml), The bistriacetylribofuranose derivative 6c (1.0 g) was the extract was dried, and the solvent removed yielding a dissolved at 0 "C in methanol (75 ml) presaturated with mixture of dimethylated species: the 2,4-dimethyl comammonia at 0 'C, and the solution was allowed t o stand pound 10, the 1,4-dimethyl compound 11, and the 3,4at 0 "C for 18 11. Evaporation of the solvent gave a color- dimethyl compound 12, in the ratios 1.00:0.27:0.02 a s less solid, which was crystallized from water and re- estimated by pmr spectroscopy, total yield 0.53 g (88%).

4-Betr:yl-vic-tri~t:ol0(4,5-b)p)~ri~I-5-01re,41 I-Benzyl-5-nitro-2-pyridone(16.5 g) in N,N-dimethylformamide (75 ml) was heated with sodium azide (9.40 g) at 93 'C for 18 11 and at 103 "C for 30 h. The product was isolated by acidification with 1 M hydrochloric acid, collection, and crystallization from aqueous ethanol, yielding 4f (14.96 g, 92%), mp 231-232 "C. Atral. calcd. for CILHION40:C 63.71, H 4.46, N 24.76; found C 63.60, H 4.30, N 24.80. For pmr spectra, see Table 1.


LYNCH

AND SHARMA

The compounds 10 and 11were separated by sublimation at 1 torr: 10 sublimed at 105 "C, and 11 at 165 "C. 2,4Dimethyl-vic-triazolo(4,5-b)pyrid-5-one,10, had mp 134 "C. At~al. calcd. for C7HRN40: C 51.21, H 4.91, N 34.13; found: C 51.19, H 4.69, N 34.44. 1,4-Dimethylvic-triazolo(4,S-b)pyrid-5-one,11, had mp 201-203 "C. Anal. found: C 51.46, H 5.32, N 34.10. For pmr and electronic spectra, see Tables I and 2. (b) Methylation of 4-methyl-vic-triazolo(4,S-b)pyrid-5one, 4e. Methylation of this species (1.0 g) in methanol (95 ml) with methyl iodide (1.0 g) in the presence of potassium carbonate ( I .O g) under the same conditions as for (a) above provided a similar mixture of dimethylated species (10, 11,12) in the same ratio as above (total yleld 0.82 g, 75%). The isomers 10 and 11 were separated by sublimation as above and characterized by mp, mixture mp, and pmr spectra. (c) Methylation of 4-p-D-ribofuranosyl-vic-triazolo(4,5-b)pyrid-5-one. The above named species 4b (1.00g) in water (5 ml) was added to a mixture of potassium carbonate (1.00 g), methyl iodide (1.00 ml), and methanol (10 ml). The reaction mixture was set aside for 18 h, solvents were removed under reduced pressure, and the residue was crystallized from water, providing 2-methyl4-p-~-ribofuranosyl-vic-triazolo(4,5-b)pyrid-5-one 9 (0.72 g, 76%), mp 210-211 "C. Anal. found: C47.12, H4.85, N 19.89. For pmr spectra, see Table 1 ; electronic spectra, see Table 2.

1037

11. M. IKEHARA, I. TAZAWA,and T. FUKUI.Biochemistry, 8, 736 (1969). 12. R. D. GUTHRIE and S. C. SMITH.Chem. Ind. 547 (1968). 13. L. Y. FOO and B. M. LYNCH.Efficient syntheses of ribosides. Abstracts, 54th Annual Meeting, Canadian Chemical Conference of the Chemical Institute of Canada, Halifax, Nova Scotia, June, 1971. 14. R. U. LEMIEUX and W. P. SHYLUK. Can. J. Chem. 31, 528 (1953). 15. U. NIEDBALLA and H. VORBRUGGEN. Angew. Chem. Int. Ed. Engl. 9, 461 (1970). 16. U. NIEDBALLA and H. VORBRUGGEN. J. Org. Chem. 39, 3654 (1974). 17. J. D. STEVENS, R. K. NESS,and H. G. FLETCHER. J. Org. Chem. 33, 1806 (1968). 18. H. M. KISSMAN, C. PIDACKS, and B. R. BAKER.J. Am. Chem. Soc. 77, 18 (1955). 19. H . U. BLANK,I. WEMPEN, and J. J. Fox. J. Org. Chem. 35, 1131 (1970). 20. J. ELGUERO and S. MIGNONAC-MONWN. Bull. Soc. Chim. Fr. 2916 (1972). T. ITOH, and K. SAITO. 21. Y. MIZUNO,M. IKEHARA, J. Org. Chem. 28, 1837 (1963). Recl. Trav. 22. K. B. DE Roos and C. A. SALEMINK. Chim. 90, 1181 (1971). 23. P. C. JAIN,S. K. CHATTERJEE, and N. ANAND.Indian J. Chem. 3, 84 (1965). 24. P. A. HARTand J. P. DAVIS.J. Am. Chem. Soc. 91, 512 (1969). Acknowledgements 25. P. A. HARTand J. P. DAVIS.J. Am. Chem. Soc. 93, Particular thanks are due to Dr. A. G. 753 (1971). 26. G. R. REVANKAR and L. B. TOWNSEND. J. HeteroMcInnes and Mr. D. G. Smith of the Atlantic cycl. Chem. 7, 117 (1970). Regional Laboratory, National Research Coun- 27. S. SENKA.K. HIROTA.and G. N. YANG. Chem. Pharm. B ~ I20. . 391 (1972); 20, 399 (1972). cil o f Canada. for the nuclear Overhauser effect G. R. REVANKAR, and and for 13C nmr data. This study 28. R. A. EARL,R: J. PUGMIRE, L. B. TOWNSEND. J. Org. Chem. 40, 1822 (1975). was assisted grants-in-aid from the 29. J. D. STEVENS and H . G. FLETCHER. J. Org. Chem. 33, Cancer Institute of Canada, the National Re1799 (1968). search Council of Canada, and the Saint Francis 30. E. J. RE]&: D. F. CALKINS. and L. GOODMAN. J. Ow. Chem. 32,169 (1967). . Xavier University council for Research. 31. J. L. IMBACH, J. L. BARASCUT, B. L. KAM,B. RAYNER, and C. TAPIERO. J. Heterocycl. Chem. 10, C. TAMBY, 1. B. L. CURRIE,R. K. ROBINS,and M. J. ROBINS.J. 1069 (1973). Heterocycl. Chem. 7, 323 (1970). 32. J. L. BARASCUT.C. TAMBY.and J. L. IMBACH.J. 2. A. BLOCH,G. DUTSCHMAN, B. L. CURRIE,R. K. Carbohydr. ~ucleosides,~"cleotides. 1, 77 (1974). ROBINS,and M. J. ROBINS.J. Med. Chem. 16,294 33. L. D. HALLand L. F. JOHNSON. Chem. Commun. (1973). 509 (1967). 3. K. IKEDA, T. SUMI,K. YOKOI,and Y. MrzuNo. Chem. 34. A. J. JONES,D. M. GRANT,M. W. WINKLEY,and Pharm. Bull. 21, 1327 (1973). R. K. ROBINS.J. Am. Chem. Soc. 92, 4079 (1970). 4. M. W. WINKLEY. J. Chem. Soc. C, 1869 (1970). 35. J. B. STOTHERS.Carbon-13 NMR spectroscopy. 5. C. L. SCHMIDT, W. J. RUSHO,and L. B. TOWNSEND. Academic Press, New York. 1972. Chem. Commun. 1515 (1971). 36. J. A. MONTGOMERY and H. J. THOMAS. J. Org. Chem. 6. B. H. RIZKALLA, A. D. BROOM,M. G. STOUT,and 36, 1962 (1971). R. K. ROBINS.J. Org. Chem. 37, 3795 (1972). 7. M. G. STOUTand R. K. ROBINS.J. Org. Chem. 33, 37. C. T. BISHOPand F. P. COOPER.Can. J. Chem. 41, 2743 (1963). 1219 (1968). J. Am. Chem. 8. M. P. SCHWEIZER, E. B. BANTA,J. T. WITKOWSKI, 38. C. ALTONAand M. SUNDARALINGAM. SOC.94, 8205 (1972). and R. K. ROBINS.J. Am. Chem. Soc. 95,3770 (1973). J. Am. Chem. 9. A. M. KAPULER, C. MONNY,and A. M. MICHELSON. 39. C. ALTONAand M. SUNDARALINGAM. SOC.95, 2333 (1973). Biochim. Biophys. Acta, 217, 18 (1970). J. Am. Chem. SOC.94, 10. A. M. KAPULER and E. REICH.Biochemistry, 10,4050 40. D. SUCKand W. SAENGER. 6520 (1972). (1971).


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41. F. E. HRUSKA. J. Am. Chem. Soc. 93, 1795 (1971). 42. H. DUGAS,B. J. BLACKBURN, R. DESLAURIERS, and I.C. P. SMITH. J. Am. Chem. Soc. 93,3468 (1971). 43. P. SINGH and D. J. HODGSON. J. Am. Chem. Soc. 96, 5276 (1974).

44. R. U. LEMIEUX, T. L. NAGABHUSAN, and B. PAUL. Can. J. Chem. 50, 773 (1972). 45. C. G. TINDALL, R . K. ROBINS, R. L. TOLMAN, and W. HUTZENLAUB. J. Org. Chem. 37, 3985 (1972).