Direct Arylation of 5-Iodouracil and 5-Iodouridine with Heteroarenes and Benzene via Photochemical Reaction

Article abstract of DOI:10.1002/hlca.201400351

A method for the direct arylation of 5-iodouracil and 5-iodouridine was found to proceed in moderate yields. By irradiating mixtures of 5-iodouracil or 5-iodouridine and a series of five-membered heterocycles such as 1H-pyrrole, furan, 2-methylfuran, 1-methyl-1H-pyrrole, thiophene, as well as benzene in MeCN/H₂O with a Hg lamp, 5-aryluracils and 5-aryluridines were synthesized. The reaction proceeded smoothly without the requirement of adding any transition metals or ligands.

Full text of DOI:10.1002/hlca.201400351

Helvetica Chimica Acta – Vol. 98 (2015)
953
Direct Arylation of 5-Iodouracil and 5-Iodouridine with Heteroarenes and
Benzene via Photochemical Reaction
by Qian Yanga)b), Tao Weia), Yun Hea), Yong Liangc), and Zun-Ting Zhang*a)
a) Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical
Chemistry, National Engineering Laboratory for Resource Development of Endangered Crude Drugs in
Northwest of China, and School of Chemistry and Chemical Engineering, Shaanxi Normal University,
Xiꢀan 710062, P. R. China (phone: þ 86-29-81530827; e-mail: zhangzt@snnu.edu.cn)
b) School of Sciences, Xiꢀan University of Technology, Xiꢀan 710054, P. R. China
c) Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199,
USA
A method for the direct arylation of 5-iodouracil and 5-iodouridine was found to proceed in
moderate yields. By irradiating mixtures of 5-iodouracil or 5-iodouridine and a series of five-membered
heterocycles such as 1H-pyrrole, furan, 2-methylfuran, 1-methyl-1H-pyrrole, thiophene, as well as
benzene in MeCN/H2O with a Hg lamp, 5-aryluracils and 5-aryluridines were synthesized. The reaction
proceeded smoothly without the requirement of adding any transition metals or ligands.
Introduction. – As important nucleoside derivatives, the 5-substituted pyrimidine
nucleosides show a broad spectrum of biological activity, such as antibacterial [1],
antifungal [2], anti-inflammatory [3], anticancer [4], and antiviral [5][6]. Bromovi-
nyldeoxyuridine (¼ 5-[(E)-2-bromoethenyl]-2’-deoxyuridine; BVDU) and derivatives
are highly selective inhibitors of varicella-zoster virus (VZV), (dideoxy)nucleoside
reverse transcriptase inhibitors (NRTIs), and non-nucleoside reverse transcriptase
inhibitors (NNRTIs) [7]. The 5-aryl substituted uracil analog cambinol also exhibits
antitumor activity as sirtuin inhibitor [8]. Moreover, 5-(furan-2-yl)-2’-deoxyuridine
was incorporated into DNA as the fluorescent probe to investigate nucleic acid
structure, dynamics, and recognition [9][10].
The arylation and heteroarylation of uracil and uracil nucleoside at the 5-position
have been accomplished efficiently using cross-coupling reactions [11]. In 1993, various
5-alkynyl derivatives were obtained in high yields (70 – 97%) by the cross-coupling
reactions of acetylated uridine triflate with several terminal alkynes [11a], and in 1991,
5-iodouridine was coupled with esters of acrylic acid in the Pd-catalyzed Heck reaction
to generate a series of esters of 5-[(E)-2-carboxyethenyl]uridine [11b]. In 2002,
Amann et al. reported the synthesis of 5-(pyren-1-yl)-2’-deoxyuridine and 8-(pyren-1-
yl)-2’-deoxyguanosine via Pd-catalyzed SuzukiÀMiyaura cross-coupling reactions
[11c]. Furthermore, in 2005, Peyron et al. synthesized 5-substituted 2’-deoxyuridine
nucleosides by the Stille reaction [11d], and in 2012, the Stille procedure was also
successful on a polyuridine RNA strand bearing 5-iodouridine base, although 60 equiv.
of 2-(tributylstannyl)furan reagent and 15 equiv. of Pd2(dba)3 catalyst along with
30 equiv. of tri(furan-2-yl)phosphine ligand were required [12]. These reactions require
ꢁ 2015 Verlag Helvetica Chimica Acta AG, Zürich

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Helvetica Chimica Acta – Vol. 98 (2015)
the preliminary preparation of organometallic reagents, which might be tricky in
several cases. Moreover, these couplings provide an organic metal salt as byproduct.
Recently, direct arylation of pyrimidine rings with Pd-activated aryl halides have
ˇ
ˇ
been established. Cernovµ et al. developed regioselective Pd-catalyzed direct CÀH
arylation of 1,3-diprotected uracil derivatives at the 5- or 6-position, controlled by the
presence or absence of CuI [13]. Pd-Catalyzed arylation of 1,3-dimethyluracil with aryl
bromides or aryl iodides were also reported to give aryluracil in recent years [14][15].
In 2014, Liang et al. synthesized 5-arylated uracils and uracil nucleosides by the Pd-
catalyzed direct arylation of 5-halouracils with arenes and electron-excessive hetero-
cycles promoted by bases [16].
Photochemistry has shown intrinsically advantageous, because activation is
achieved by the absorption of a photon, which leaves no residue, whereas most
catalytic methods involve the use of toxic/polluting reagents [17]. Furthermore, the
reactions occur under unparalleled mild conditions and, in many cases, deep-seated
chemical transformations occurring in high yields and with high selectivity. To
investigate whether pyrimidyne was an intermediate, Youssefyeh and Lichtenberg
reported the photolysis of 5,6-diiodo-1,3-dimethyluracil in benzene and in furan, which
gives products derived from a radical intermediate [18]. Herein, we would like to
report the synthesis of 5-arylated uracil and uracil nucleoside by the photo-induced
cross coupling of 5-iodouracil and 5-iodouridine with heteroaromatics and benzene
under the Hg light, which did not cause the cleavage of the nucleoside-glycosidic bond
and was suitable for the natural (N(3) and OH unprotected) uridines and uracils
(Scheme 1).
Scheme 1. Steps for the Photochemical Synthesis of Heteroaryluracils and Heteroaryluridines
Results and Discussion. – Initially, 5-iodouracil (1a; 0.2 mmol) and 1H-pyrrole (2a;
6 mmol) were dissloved in MeOH (40 ml) and irradiated with a Hg lamp (500 W) at
208. After 7 h, the solution appeared yellow, indicating release of I2 from 5-iodouracil to
the solution, and 1a disappeared as judged by TLC. The arylated product 3a (yield
10%) was isolated, and its structure was confirmed by means of NMR and HR-MS
(Table 1, Entry 1). Then, a systematic investigation, with different solvents and
concentrations of 2a, was carried out, and the results are listed in Table 1. In DMF and
AcOEt, only a trace of 3a was obtained (Entries 2 and 3), and in CH2Cl2 and iPrOH,
the yield of product 3a was lower than that in MeOH (Entries 4 and 5). Eventually, the
yield of 3a obtained in MeCN was 28% (Entry 6). Then, H2O was added as a co-solvent
to improve the solubility of 1a and to reduce the amount of organic solvents. When a
mixture of MeCN/H2O (1:1) was used, the yield of 3a was increased to 37% with no

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Table 1. Optimization of Photochemical Synthesis of 5-(1H-Pyrrol-2-yl)uracila)
Entry
Solvent
Concentration of 2a [m]
Base
Yield b) [%]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
MeOH
DMF
AcOEt
CH2Cl2
iPrOH
MeCN
MeCN/H2O 1 : 1
MeCN/H2O 1 : 1
MeCN/H2O 1 : 1
MeCN/H2O 1 : 1
MeCN/H2O 1 : 1
MeCN/H2O 1 : 1
MeCN/H2O 1 : 1
MeCN/H2O 1 : 1
MeCN/H2O 1 : 1
MeCN/H2O 1 : 1
1.5 Â 10À1
1.5 Â 10À1
1.5 Â 10À1
1.5 Â 10À1
1.5 Â 10À1
1.5 Â 10À1
1.5 Â 10À1
4 Â 10À2
–
–
–
–
–
–
–
–
10
Trace
Trace
6
8
28
37
20
43
51
40
45
41
43
53
60
2 Â 10À1
–
–
–
2.5 Â 10À1
3.5 Â 10À1
2.5 Â 10À1
2.5 Â 10À1
2.5 Â 10À1
2.5 Â 10À1
2.5 Â 10À1
NaOH
K2CO3
NaHCO3
Et3N
AcONac)
a) Couplings were performed by irradiating 0.2 mmol of 5-iodouracil (1a; 5 Â 10À3 m), 6 – 14 mmol of 1H-
pyrrole (2a; 1.5 Â 10À1 – 3.5 Â 10À1 m), and 0.2 mmol of base in 40 ml of solvent with a Hg lamp at 208 for
7 h under Ar. b) Yield of isolated material after column chromatography on silica gel. c) In the cases of
0.1 and 0.3 mmol of AcONa, the yields of 3a were 55 and 58%, respectively.
significant byproduct (Entry 7). Therefore, a mixture of MeCN/H2O (1:1) was chosen
as the reaction medium for all further reactions.
Changing the concentration of 1H-pyrrole (2a) is another possibility for increasing
the yield of product 3a. When increasing the amount of the starting 2a up to 2.5 Â
10À1 m, a good yield of 3a (51%) was obtained (Entry 10). However, the yield of 3a
decreased significantly when the concentration of 2a was increased up to 3.5 Â 10À1
m
(Entry 11).
In the presence of base, the yield of 6-aryl/alkyl BINOLs were improved by the
photochemistry reaction [19]. Next, we investigated the arylation of 5-iodouracils 1a in
the presence of an organic or inorganic base. The result indicated that an equimolar
amount of organic base can increase the yields of 3a significantly (Entry 12 – 16), and
the best yield is 60% with AcONa as the base (Entry 16).
With the optimized reaction conditions in hand, the coupling of a variety of
heteroaromatics, benzene (2) and 5-iodouracil or 5-iodouridine 1 has been studied to
illustrate the photochemical synthesis of aryluracil and aryluridine. When the five-
membered heterocycles 2 were reacted with 5-iodouracil (1a), the yields of 3 were
generally higher than those with 5-iodouridine (1b; Table 2, Entries 1 – 8). The

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Table 2. Synthesis of Heteroaryluracils and Heteroaryluridines by Photochemical Reactiona)
Entry
1
2
3
Yieldb) [%]
1
2
3
4
5
6
7
8
9
1a
1a
1a
1b
1b
1b
1b
1b
1a
1a
1b
1b
1H-Pyrrole
Furan
1-Methyl-1H-pyrrole
Furan
1H-Pyrrole
Thiophene
2-Methylfuran
1-Methyl-1H-pyrrole
Benzene
3a
3b
3c
3d
3e
3f
3g
3h
3i
60
55
64
28
35
23
32
41
10
79c)
7
10
11
12
Benzene
Benzene
Benzene
3i
3j
3j
46c)
a) Irradiating 0.2 mmol of 1 (5 Â 10À3 m), 6 mmol of 2 (2.5 Â 10À1 m), and 0.2 mmol of AcONa (5 Â
10À3 m) in MeCN/H2O (40 ml) with a Hg lamp at 208 for 7 h under Ar. b) Yield of isolated product
after column chromatography on silica gel. c) 0.2 mmol of 1 (5 Â 10À3 m), 110 mmol of benzene (3m), and
0.2 mmol of AcONa (5 Â 10À3 m) in MeCN/H2O 5 : 1 (30 ml).
electron-donating heterocycles 2 were efficient to give the product 3 in good yield. For
2-methylfuran and furan coupling with the same substrate 1b by the photochemical
reaction, the yield of 3g was higher than that of 3d (Entries 4 and 7). Meanwhile, for
1H-pyrrole and 1-methyl-1H-pyrrole, the yield of 3h was higher than that of 3e
(Entries 5 and 8). Because the electron density of benzene is lower than that of five-
membered heterocycles, the yield of 5-phenyluracil and 5-phenyluridine decreased to
10 and 7%, respectively (Entries 9 and 11). Increasing the concentration of benzene to
3m, the best yields of 5-phenyluracil (79%) and 5-phenyluridine (46%) were obtained
(Entries 10 and 12).
A plausible mechanism for the formation of 3 is proposed in Scheme 2. First, under
the radiation of UV light, the photoinduced homocleavage of the CÀI bond of A gave
Scheme 2. Mechanism for the Synthesis of Heteroaryluracils and Heteroaryluridines

Helvetica Chimica Acta – Vol. 98 (2015)
957
the uracil radical B. Then, B was coupled with heteroaromatics or benzene to afford an
intermediate C, and elimination of H· provided the desired coupled product D.
Conclusions. – In summary, we have demonstrated that the radical arylation of 5-
iodouracil and 5-iodouridine with heteroaromatics and benzene in MeCN/H2O gave 5-
arylated uracil and uracil nucleoside in good yield. The radical arylation protocol
developed here avoids the usage of organometallic precursors which are necessary for
Suzuki or Stille coupling. It proceeded smoothly without the requirement of adding any
transition metals or ligands. Compared with the photoreaction reported by Youssefyeh
and Lichtenberg [18], we not only optimized the solvent of photoreaction and improved
the yield of 5-arylated uracil, but also the uracil nucleosides 5-arylated with 1H-pyrrole
and thiophene were synthesized. The presented reaction was also compatible with
natural nucleoside, as no glycosidic bond cleavage was observed, and no protecting
group was required.
This research was supported by the National Natural Science Foundation of China (No. 21372150),
the Fundamental Research Funds for the Central Universities (No. GK261001095), and the Science and
Innovation Funds of Graduate Programs of Shaanxi Normal University (No. 2009CXS013).
Experimental Part
General. All the irradiation experiments were performed in a BL-GHX-V photochemical reactor
equipped with a 500-W high-pressure Hg lamp. TLC: Silica gel 60 GF254 (SiO2; Qingdao Haiyang
Chemistry Plant, Qingdao, P. R. China). Column chromatography (CC): SiO2 (200 mesh; Qingdao
Haiyang Chemistry Plant); CH2Cl2/MeOH 20 :1 as eluent. M.p.: X-5 micro melting point apparatus;
uncorrected. IR Spectra: Nicolet 170SX FT-IR spectrophotometer with KBr pellets; n˜ in cmÀ1. 1H- and
13C-NMR Spectra: Bruker AM-400 Advance spectrometer at 400 (1H) and 100 (13C) MHz, resp.; in
(D6)DMSO; d in ppm rel. to (D6)DMSO solvent peaks, J in Hz. HR-MS: Bruker MALDI-TOF-MS
using ESI technique; in m/z.
Procedure for Synthesis of 5-Iodouracil (1a) [20]. Uracil (0.33 g, 3 mmol), I2 (1.52 g, 6 mmol), and
(NH4)2Se(NO3)6 (0.82 g, 1.5 mmol) were added into an oven-dried round-bottom flask with 100 ml of
MeCN, and the resulting mixture was stirred at r.t. for 3 d until a white precipitation appeared. Then, the
residue was filtered and washed with Et2O (20 ml) to afford 1a (0.67 g, 95%) as white powder. 5-
Iodouridine (1b) was obtained by the same method as 1a.
Synthesis of 5-(1H-Pyrrol-2-yl)uracil (3a). A soln. of 1a (0.05 g, 0.2 mmol), 1H-pyrrole (2a; 0.67 g,
10 mmol), and AcONa (0.02 g, 0.2 mmol) in MeCN/H2O 1:1 (40 ml) in a 50-ml quartz tube was
deaerated by bubbling Ar for 30 min and irradiated for 7 h with a high-pressure Hg lamp (500 W), which
was cooled to ca. 208 with tap water by means of an internal cold finger. The progress of reaction was
monitored by TLC at regular intervals. Then, the solvent was removed under reduced pressure, and the
residue was separated by CC (SiO2) to give the corresponding product 3a (0.02 g, 60%). Compounds
3b – 3h were obtained by the same method as 3a.
Synthesis of 5-Phenyluracil (3i). A soln. of 1a ( 0.05 g, 0.2 mmol), benzene (8.7 g, 0.11 mol), and
AcONa (0.02 g, 0.2 mmol) in MeCN/H2O 5 :1 (30 ml) in a 50-ml quartz tube was deaerated by bubbling
Ar for 30 min and irradiated for 7 h with a high-pressure Hg lamp (500 W) at 208. The reaction was
stopped until lots of white precipitation appeared in aq. phase. Then, the resulting suspension was
filtered. The residue was dissolved in DMSO and precipitated in H2O again. The process was repeated
until the product 3i was obtained (0.03 g, 79%).
Synthesis of 5-Phenyluridine (3j). Benzene (8.7 g, 0.11 mol) and AcONa (0.02 g, 0.2 mmol) were
added to a stirring soln. of 1b (0.07 g, 0.2 mmol) in MeCN/H2O 5 :1 (30 ml) in a 50-ml quartz tube at r.t.,
followed by degasing with Ar for 30 min. The resulting soln. was irradiated by a high-pressure Hg

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lamp (500 W) for 7 h. After being cooled down to r.t., the volatiles were removed under the reduced
pressure, and the residue was separated by CC (SiO2; CH2Cl2/MeOH 20 :1) to give 3j (30 mg, 46%) as
white solid.
5-(1H-Pyrrol-2-yl)uracil (3a) [21]. Grey powder. M.p. 276.7 – 280.08. IR (KBr): 3401, 2815, 1746,
1
1661, 1405, 1239, 1103, 842, 720, 657, 555, 450. H-NMR: 11.25 (s, HÀN(1’), 11.04 (d, J ¼ 4.7, HÀN(1));
10.84 (s, HÀN(3)), 7.70 (d, J ¼ 5.9, HÀC(6)); 6.73 (dd, J ¼ 4.1, 2.5, HÀC(5’)); 6.49 (t, J ¼ 3.6, HÀC(4’));
6.01 (dd, J ¼ 5.8, 2.6, HÀC(3’)). 13C-NMR: 162.8; 150.4; 134.7; 123.9; 117.7; 107.8; 106.1; 105.9. HR-ESI-
MS: 200.0425 ([M þ Na]þ, C8H7N3NaOþ2 ; calc. 200.0436).
5-(Furan-2-yl)uracil (3b) [22]. White powder. M.p. 291.0 – 295.78. IR (KBr): 3211, 2829, 1738, 1681,
1638, 1440, 1348, 1237, 999, 765, 728, 654, 556, 453. 1H-NMR: 11.39 (s, HÀN(1)), 11.19 (s, HÀN(3)), 7.71 (s,
HÀC(6)); 7.63 (s, HÀC(5’)); 6.83 (s, HÀC(4’)); 6.51 (s, HÀC(3’)). 13C-NMR: 161.1; 150.3; 146.7; 141.2;
136.2; 111.5; 107.3; 104.4. HR-ESI-MS: 201.0263 ([M þ Na]þ, C8H6N2NaO3þ ; calc. 201.0276).
5-(1-Methyl-1H-Pyrrol-2-yl)uracil (3c) [22a][23]. Grey powder. M.p. 257.3 – 261.38. IR (KBr): 3043,
2827, 1749, 1679, 1638, 1495, 1447, 1420, 1314, 1226, 1210, 767, 711, 642, 549, 437, 421. 1H-NMR: 11.24 (s,
HÀN(1)); 11.06 (s, HÀN(3)); 7.38 (s, HÀC(6)); 6.77 (s, HÀC(5’)); 5.96 (s, HÀC(3’,4’)); 3.35 (s, MeN).
13C-NMR (151 MHz, (D6)DMSO): 163.2; 151.2; 141.2; 125.6; 123.2; 109.4; 106.6; 105.8; 34.2. HR-ESI-
MS: 214.0581 ([M þ Na]þ, C9H9N3NaOþ2 ; calc. 214.0592).
5-(Furan-2-yl)uridine (3d) [16][24]. Yellow powder. M.p. 234.8 – 238.18. IR (KBr): 3407, 3067, 1692,
1639, 1569, 1472, 1384, 1260, 1092, 1036, 990, 930, 747, 406. 1H-NMR: 11.65 (s, HÀN(3)); 8.42 (s, HÀC(6));
7.61 (s, HÀC(5’’)); 6.87 (d, J ¼ 2.8, HÀC(3’’)); 6.59 – 6.48 (m, HÀC(4’’)); 5.87 (d, J ¼ 4.9, HÀC(2’)); 5.42 (d,
J ¼ 4.8, HOÀC(3’)); 5.20 (s, HOÀC(4’)); 5.11 (d, J ¼ 2.5, HOÀC(6’)); 4.12 (d, J ¼ 4.1, HÀC(3’)); 4.03 (d,
J ¼ 3.1, HÀC(4’)); 3.91 (d, J ¼ 1.9, HÀC(5’)); 3.69 (d, J ¼ 11.6, 1 H, CH2(6’)); 3.60 (d, J ¼ 11.6, 1 H,
CH2(6’)). 13C-NMR: 160.1; 149.7; 146.4; 141.5; 134.9; 111.5; 107.9; 105.6; 88.2; 84.9; 74.0; 69.8; 60.6. HR-
ESI-MS: 333.0683 ([M þ Na]þ, C13H14N2NaO7þ ; calc. 333.0699).
5-(1H-Pyrrol-2-yl)uridine (3e) [16]. Grey powder. M.p. 223.4 – 227.08. IR (KBr): 3407, 3067, 2856,
1639, 1569, 1466, 1284, 1260, 1092, 990, 930, 747, 406. 1H-NMR: 11.57 (s, HÀN(1’’)); 10.84 (s, HÀN(3));
8.22 (s, HÀC(6)); 6.77 (s, HÀC(5’’)); 6.39 (s, HÀC(3’’)); 6.04 (d, J ¼ 2.7, HÀC(4’’)); 5.84 (d, J ¼ 5.0,
HÀC(2’)); 5.41 (d, J ¼ 5.6, HOÀC(3’)); 5.25 (t, J ¼ 4.5, HOÀC(4’)); 5.09 (d, J ¼ 5.2, HOÀC(6’)); 4.15 (dd,
J ¼ 10.3, 5.1, HÀC(3’)); 4.04 (dd, J ¼ 9.5, 4.8, HÀC(4’)); 3.88 (d, J ¼ 3.6, HÀC(5’)); 3.75 – 3.67 (m, 1 H,
CH2(6’)); 3.64 – 3.57 (m, 1 H, CH2(6’)). 13C-NMR: 162.0; 149.7; 133.6; 124.0; 118.4; 108.1; 107.4; 105.6;
88.2; 84.8; 73.6; 69.8; 60.7. HR-ESI-MS: 332.0838 ([M þ Na]þ, C13H15N3NaO6þ ; calc. 332.0859).
5-(Thiophen-2-yl)uridine (3f) [16][25]. Grey-white powder. M.p. 208.0 – 212.78. IR (KBr): 3337,
1
2922, 2829, 1719, 1688, 1645, 1471, 1340, 1262, 1243, 1046, 992. H-NMR: 11.71 (s, HÀN(3)), 8.67 (s,
HÀC(6)); 7.47 (d, J ¼ 5.1, HÀC(5’’)); 7.41 (d, J ¼ 3.1, HÀC(3’’)); 7.07 – 7.05 (m, HÀC(4’’)); 5.85 (d, J ¼ 4.2,
HÀC(2’)); 5.49 (d, J ¼ 5.3, HOÀC(3’)); 5.45 (t, J ¼ 4.6, HOÀC(4’)); 5.11 (d, J ¼ 5.5, HOÀC(6’)); 4.14 (dd,
J ¼ 9.4, 4.7, HÀC(3’)); 4.07 (dd, J ¼ 10.0, 5.0, HÀC(4’)); 3.94 – 3.91 (m, HÀC(5’)); 3.79 – 3.74 (m, 1 H,
CH2(6’)); 3.68 – 3.63 (m, 1 H, CH2(6’)). 13C-NMR: 161.3; 149.6; 135.7; 133.9; 126.4; 125.7; 122.5; 108.3;
88.7; 84.6; 74.3; 69.4; 60.2. HR-ESI-MS: 349.0452 ([M þ Na]þ, C13H14N2NaO6Sþ; calc. 349.0470).
5-(5-Methylfuran-2-yl)uridine (3g). Yellow powder. M.p. 230.0 – 234.28. IR (KBr): 3327, 2828, 1719,
1656, 1597, 1542, 1261, 1090, 1045, 1018, 790. 1H-NMR: 11.60 (s, HÀN(3)); 8.41 (s, HÀC(6)); 6.72 (d, J ¼
2.9, HÀC(3’’)); 6.11 (d, J ¼ 2.7, HÀC(4’’)); 5.86 (d, J ¼ 4.8, HÀC(2’)); 5.44 (d, J ¼ 5.4, HOÀC(3’)); 5.22 (d,
J ¼ 4.3, HOÀC(4’)); 5.11 (d, J ¼ 5.1, HOÀC(6’)); 4.14 – 4.09 (m, HÀC(3’)); 4.07 – 4.01 (m, HÀC(4’)); 3.91
(s, HÀC(5’)); 3.71 (d, J ¼ 11.5, 1 H, CH2(6’)); 3.62 (d, J ¼ 11.8, 1 H, CH2(6’)); 2.29 (s, Me(5’’)). 13C-NMR:
160.1; 150.4; 149.6; 144.7; 134.0; 108.9; 107.5; 105.8; 88.2; 84.7; 74.0; 69.7; 60.4; 18.50. HR-ESI-MS:
347.0836 ([M þ Na]þ , C14H16N2NaOþ7 ; calc. 347.0855).
5-(1-Methyl-1H-Pyrrol-2-yl)uridine (3h). White powder. M.p. 115.3 – 118.98. IR (KBr): 3399, 3067,
2829, 1680, 1541, 1490, 1456, 1412, 1310, 1248, 1056, 725, 406. 1H-NMR: 11.53 (s, HÀN(3)); 7.96 (s,
HÀC(6)); 6.79 (t, J ¼ 2.0, HÀC(5’’)); 5.98 (dd, J ¼ 5.7, 2.8, HÀC(3’’,4’’)); 5.85 (d, J ¼ 5.4, HÀC(2’)); 5.41 (d,
J ¼ 5.7, HOÀC(6’)); 5.09 (t, J ¼ 4.7, HOÀC(3’,4’)); 4.11 (dd, J ¼ 10.6, 5.3, HÀC(4’)); 3.99 (dd, J ¼ 9.0, 4.6,
HÀC(3’)); 3.87 (d, J ¼ 3.0, HÀC(5’)); 3.61 (dt, J ¼ 7.3, 4.1, 1 H, CH2(6’)); 3.56 – 3.52 (m, 1 H, CH2(6’)); 3.35
(d, J ¼ 2.1, MeN’). 13C-NMR: 169.5; 163.1; 152.6; 150.9; 139.6; 135.9; 133.3; 128.1; 128.0; 127.9; 127.6;
126.9; 112.1; 52.9. HR-ESI-MS: 346.0996 ([M þ Na]þ, C14H17N3NaO6þ ; calc. 346.1015).

Helvetica Chimica Acta – Vol. 98 (2015)
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5-Phenyluracil (3i) [26]. White powder. M.p. 238.6 – 239.28. IR (KBr): 3033, 2822, 1764, 1675, 1504,
1448, 1424, 1235, 1279, 1170, 759, 687, 788, 594, 551, 506, 460, 432. 1H-NMR: 11.20 (d, J ¼ 60.0, HÀN(1,3));
7.62 (s, HÀC(6)); 7.54 (d, J ¼ 7.6, HÀC(2’,6’)); 7.36 (t, J ¼ 7.6, HÀC(3’,5’)); 7.28 (t, J ¼ 7.3, HÀC(4’)).
13C-NMR: 163.2; 151.2; 141.2; 125.6; 123.2; 109.5; 106.6; 105.9. HR-ESI-MS: 211.0467 ([M þ Na]þ,
C10H8N2NaOþ2 ; calc. 211.0483).
5-Phenyluridine (3j) [27]. Grey-white powder. M.p. 190.4 – 192.78. IR (KBr): 3244, 2828, 1703, 1648,
1602, 1495, 1421, 1387, 1340, 1243, 1100, 1065, 1016, 989, 788, 750, 698,589. 1H-NMR: 11.53 (s, HÀN(3));
8.29 (s, HÀC(6)); 7.56 (d, J ¼ 7.4, HÀC(3’’,5’’)); 7.37 (t, J ¼ 7.5, HÀC(2’’,6’’)); 7.31 (t, J ¼ 7.3, HÀC(4’’)); 5.86
(d, J ¼ 4.6, HÀC(2’)); 5.44 (d, J ¼ 5.5, HOÀC(3’)); 5.22 (t, J ¼ 4.5, HOÀC(4’)); 5.09 (d, J ¼ 5.3, HOÀC(6’));
4.16 (dd, J ¼ 9.8, 4.8, HÀC(3’)); 4.05 (dd, J ¼ 9.3, 4.6, HÀC(4’)); 3.90 (s, HÀC(5’)); 3.71 – 3.64 (m, 1 H,
CH2(6’)); 3.62 – 3.55 (m, 1 H, CH2(6’)). 13C-NMR: 162.1, 150.1, 138.1, 133.1, 128.1, 127.9, 127.1, 113.4, 88.3,
84.7, 73.9, 69.6, 60.4. HR-ESI-MS: 343.0891 ([M þ Na]þ, C15H16N2NaO6þ ; calc. 343.0906).
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Received November 4, 2014