Synthesis and antiviral evaluation of 2'-C-methyl analogues of 5-alkynyl- and 6-alkylfurano- and pyrrolo[2,3-d]pyrimidine ribonucleosides

Article abstract of DOI:10.1080/15257770903128870

A series of novel 2'-C-methylribonucleosides, involving 5-iodo and 5-alkynyl uridine analogues as well as related bicyclic furano- and pyrrolo[2,3-d]pyrimidinone compounds, has been synthesized and evaluated for their inhibitory effect on replication of t

Full text of DOI:10.1080/15257770903128870

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Synthesis and Antiviral Evaluation of
2′-C-Methyl Analogues of 5-Alkynyl-
and 6-Alkylfurano- and Pyrrolo[2,3-
d]Pyrimidine Ribonucleosides
Piotr Januszczyk a , Joanna Fogt a , Jerzy Boryski a , Kunisuke Izawa
b , Tomoyuki Onishi b , Johan Neyts c & Erik De Clercq c
a Institute of Bioorganic Chemistry, Polish Academy of Sciences,
Poznan, Poland
b Aminoscience Laboratories, Ajinomoto Co. Inc., Kawasaki-ku,
Kawasaki, Japan
c Rega Institute for Medical Research, Katholieke Universiteit
Leuven, Leuven, Belgium
Version of record first published: 29 Jul 2009.
To cite this article: Piotr Januszczyk, Joanna Fogt, Jerzy Boryski, Kunisuke Izawa, Tomoyuki Onishi,
Johan Neyts & Erik De Clercq (2009): Synthesis and Antiviral Evaluation of 2′-C-Methyl Analogues of
5-Alkynyl- and 6-Alkylfurano- and Pyrrolo[2,3-d]Pyrimidine Ribonucleosides, Nucleosides, Nucleotides
and Nucleic Acids, 28:5-7, 713-723
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Nucleosides, Nucleotides and Nucleic Acids, 28:713–723, 2009
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1525-7770 print / 1532-2335 online
DOI: 10.1080/15257770903128870
SYNTHESIS AND ANTIVIRAL EVALUATION OF 2ꢀ-C-METHYL
ANALOGUES OF 5-ALKYNYL- AND 6-ALKYLFURANO- AND
PYRROLO[2,3-d]PYRIMIDINE RIBONUCLEOSIDES
Piotr Januszczyk,1 Joanna Fogt,1 Jerzy Boryski,1 Kunisuke Izawa,2
Tomoyuki Onishi,2 Johan Neyts,3 and Erik De Clercq3
1Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
2Aminoscience Laboratories, Ajinomoto Co. Inc., Kawasaki-ku, Kawasaki, Japan
3Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium
A series of novel 2ꢁ-C-methylribonucleosides, involving 5-iodo and 5-alkynyl uridine analogues
2
as well as related bicyclic furano- and pyrrolo[2,3-d]pyrimidinone compounds, has been synthesized
and evaluated for their inhibitory effect on replication of the hepatitis C virus (HCV). The new
nucleoside analogues did not show meaningful anti-HCV activity.
Keywords Nucleoside analogues; 2ꢁ-C-methylnucleosides; furano- and pyrrolo[2,3-
d]pyrimidine nucleosides
INTRODUCTION
It has been shown that transformation of pyrimidine nucleosides into
their bicyclic 6-alkyl-2,3-dihydrofurano[2,3-d]-pyrimidin-2(1H)-one or 6-
octyl-2,3-dihydropyrrolo[2,3-d]-pyrimidin-2(3H,7H)-one derivatives results
in interesting biological properties. The type of biological activity, potency
and selectivity, depend on structural factors: (1) structure of the sugar or
pseudosugar moiety, and (2) the length of lipophilic alkyl substituent in
the 6-position. Thus, the furanopyrimidine compounds are the most potent
and selective inhibitors of varicella-zoster virus (VZV) as 2ꢁ-deoxynucleosides
equiped with C8 to C10 alkyl chains.[1–3] In turn, 2ꢁ3ꢁ-dideoxynucleosides
and their cyclopentyl analogues are not active against VZV but show
selective and specific activity against human cytomegalovirus (HCMV).[4]
Received 3 March 2009; accepted 11 May 2009.
In honor and celebration of the 70th birthday of Professor Morris J. Robins.
Address correspondence to Jerzy Boryski, Institute of Bioorganic Chemistry, Polish Academy of
Sciences, Noskowskiego 12/14PL-61704, Poznan, Poland. E-mail: jboryski@ibch.poznan.pl
713

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P. Januszczyk et al.
Replacement of the 2-deoxyribofuranosyl moiety by the acyclovir-type 3-[(2-
hydroxyethoxy)methyl] chain considerably diminishes the antiviral proper-
ties of the furano[2,3-d]-pyrimidine system.[5] On the other hand, it has
been demonstrated that some analogous acyclonucleosides exhibit activity
against human immunodeficiency virus (HIV) and herpes simplex virus
(HSV) at micromolar concentrations.[6] Further, SAR studies have indi-
cated that furanopyrimidine nucleosides are, in general, more active than
related pyrrolopyrimidine compounds.[7] In turn, 3-(β-d-ribofuranosyl)-
6-decyl-2,3-dihydrofurano[2,3-d]pyrimidin-2-on shows moderate anti-HCV
activity in HCV replicon system and efficiently inhibits bovine viral diar-
rhea virus (BVDA).[8a] More recently, a series of furano- and pyrrolo[2,3-
d]pyrimidine nucleoside 5ꢁ-O-triphosphates have been tested for their
substrate properties toward some RNA and DNA polymerases to show
that only the 6-hexylfurano compound is recognized by calf thymus ter-
minal deoxynucleotidyl transferase (TDT) and HIV reverse transcriptase
(RT).[8]
From a synthetic viewpoint, furano[2,3-d]pyrimidine nucleosides can
be efficiently prepared from the respective 5-iodouracil derivatives and
alkynes under Sonogashira cross-coupling conditions. Depending on the
temperature and the Pd-catalyst used, the reaction may proceed directly
to fluorescent furano[2,3-d]pyrimidine products,[9] or to intermediate 5-
(alkyn-1-yl)uracil nucleosides.[10] The latter compounds may then undergo
an intramolecular cyclization to bicyclic furanopyrimidine nucleosides in
a palladium-copper catalyzed reaction.[1–8,10] The 5-(alkyn-1-yl)uracil nu-
cleoside analogues demonstrate in vitro inhibitory activity against HSV-
1, HSV-2, and vaccinia virus (VV).[11] The related acyclonucleosides
with 1-[(2-hydroxyethoxy)methyl] pseudosugar portion exhibit moderate
anti-HIV activity,[6] while the corresponding arabinofuranosyl, 2ꢁ-deoxy-2ꢁ-
fluororibofuranosyl, and 2ꢁ,3ꢁ-dideoxyfuranosyl derivatives were found to be
active against Mycobacteria.[12,13]
In continuation of our study on the chemistry and biology of base-
modified 2ꢁ-C-β-methylnucleosides,[14,15] we synthesized a new series of
5-(alkyn-1-yl)uracil, furano[2,3-d]pyrimidine and pyrrolo[2,3-d]pyrimidine
nucleosides, in order to evaluate the compounds for their antiviral prop-
erties. The 2ꢁ-C-branched nucleoside analogues are promising synthetic
targets due to their potent antiviral activity against RNA viruses, including
the hepatitis C virus (HCV). One of the most active compounds of this
type is 2ꢁ-C-β-methylcytidine, a potent and selective inhibitor of the repli-
cation of Flaviviridae in cell culture.[16–18] A number of its new derivatives
modified within the sugar portion has been obtained, including 2ꢁ-deoxy-
[19,20]
and 3ꢁ-deoxyribosides,[21] 2ꢁ-C-β-methyl-1-(β-d-xylofuranoside,[21] 2ꢁ-
fluoro[22] and 3ꢁ-fluoro[21] derivatives, the 3ꢁ-O-valyl ester,[18] and the 3ꢁ-
methoxynucleoside.[21] Modifications of the pyrimidine moiety have re-
ceived relatively minor attention.[14] Herein, we report the synthesis and

2ꢁ-C-Methyl Analogues
715
antiviral evaluation of a novel series of 2ꢁ-C-β-methylribosides of 5-(alkyn-1-
yl)uracil, furano[2,3-d]pyrimidine and pyrrolo[2,3-d]pyrimidine.
RESULTS AND DISCUSSION
The starting nucleoside synthon, tri-O-benzoyl-5-iodo-2ꢁ-C-β-
methyluridine (3) was obtained in the direct coupling reaction of
5-iodouracil (1) and 1,2,3,5-tetra-O-benzoyl-2-C-methyl-β-d-ribofuranose
(2) under Vorbru¨ggen conditions (Scheme 1). Because 5-iodopyrimidine
SCHEME 1 Reagents and conditions: (i) BSA, CH2Cl2, room temperature, 20 minutes, then SnCl4,
room temperature, 24 hours; (ii) 0.1 M MeONa, room temperature, 24 hours; (iii) NH3/MeOH, room
temperature, 24 hours; (iv) 1-alkyne, Pd(Ph3P)4, CuI, Et3N, DMF, Ar, room temperature, 19 hours; (v)
1-alkyne, 10% Pd/C, CuI, Et3N, MeCN, Ar, 80◦C, 5 hours; (vi) NH3/MeOH, 50◦C, 48 hours.

716
P. Januszczyk et al.
nucleosides had never been synthesized in the 2ꢁ-C-branched series, we
decided to include the compound in the antiviral screening. Therefore,
the tri-O-benzoyl derivative 3 was deprotected with sodium methoxide in
methanol (method A) or with methanolic ammonia (method B) to get
5-iodo-2ꢁ-C-β-methyluridine (4).
To prepare 5-alkynyl and furano[2,3-d]pyrimidine products, compound
3 was treated with 1-alkynes under the Sonogashira coupling conditions.
Depending on reaction temperature and the nature of palladium catalyst
used, we were able to obtain either 5-alkynyluridine analogues (5, 6), or
the bicyclic furano nucleosides (9, 10). Thus, reaction of 3 with 1-decyne
or 1-dodecyne in the presence of tetrakis(triphenylphosphine)palladium(0)
[Pd(Ph3P)4] performed at room temperature gave the respective 5-decyn-
1-yl (5) and 5-dodecyn-1-yl (6) nucleosides as main products. The tri-O-
benzoyl derivtives 5 and 6 were then treated with methanolic ammonia to
give nucleosides 7 and 8.
In turn, the coupling reaction of 3 and 1-alkynes at higher temper-
ature (80◦C) and catalyzed by 10% Pd/C resulted in the formation of
fluorescent, bicyclic 6-decyl and 6-dodecyl furanopyrimidine nucleosides
(compounds 9 and 10, respectively), which were deprotected to 11 and 12
by using methanolic ammonia. Interestingly, the use of sodium methoxide
in methanol instead of NH3/MeOH in an attempted debenzoylation of 9
resulted in an almost equimolar mixture of 11 and a new pyrimidine nucle-
oside, 4-O-methyl-5-(2-oxodecyl)-2ꢁ-C-β-methyluridine (13). The formation
of 13 can be due to a nucleophilic attack of the methoxide anion at C7a
of the furano[2,3-d]pyrimidine system and the subsequent ring opening.
The ring-opening reaction is reversible. For instance, treatment of 13 with
saturated solution of NH3/MeOH at 50◦C for 48 hours gave the pyrrolo[2,3-
d]pyrimidine derivative (14) as a single product. For a preparative scale,
however, 6-octyl- and 6-decyl-pyrrolo[2,3-d]pyrimidine nucleosides (14, 15)
were prepared directly from the respective furano compounds (11, 12).
The newly synthesized compounds: 5-iodo- (4) and 5-alkynyluridine
analoges (5, 6), 6-alkyl furanopyrimidine nucleosides (11, 12), their 6-alkyl
pyrrolopyrimidine congeners (14, 15), and ring-opened analogue (13) were
examined using HCV subgenomic replicon system in Huh-5–2-cells. The
compounds 4 and 13 were inactive as antiviral agents. The other nucleosides
demonstrated low anti-HCV activity (EC50 in the range of 31–85 µM).
EXPERIMENTAL
General Procedures
1,2,3,5-Tetra-O-benzoyl-2-C-β-methyl-β-d-ribofuranose (2) was obtai-
ned.[16] Melting points were determined on a Laboratory Devices Mel-Temp
II micromelting points apparatus (Laboratory Devices, Holliston, MA, USA)

2ꢁ-C-Methyl Analogues
717
and are uncorrected. UV spectra were measured on a Beckman DU-65
1
spectrophotometer (Beckman, South Pasadena, CA, USA). The H (300
MHz) and 13C NMR (75.5 MHz) spectra were recorded on a Varian Unity
300 FT NMR 300 MHz spectrometer (Varian, Palo Alto, CA, USA) in
DMSO-d6 with tetramethylsilane as an internal standard: chemical shifts are
reported in δ-values (ppm), and coupling constants are given in Hz. High
resolution mass spectra (HRMS) were taken on an AMD-604 spectrometer
(AMD Intectra GmbH, Harpstedt, Germany) using the LSIMS technique
(Cs+, 9 keV; in NBA). Thin-layer chromatography (TLC) was conducted on
Merck silica gel 60 F254 plates (E. Merck, Darmstadt, Germany) using the
following solvent systems (measured by volume): A, chloroform-methanol
(95:5); B, ethyl acetate-hexane (2:1); C, ethyl acetate-toluene (2:1). For
preparative short-column chromatography Merck TLC gel H 60 was used.
5-Iodo-2ꢁ,3ꢁ,5ꢁ-tri-O-benzoyl-2ꢁ-C-β-methyl-D-uridine (3)
BSA (0.6 mL, 2.4 mmol) was added to an anhydrous suspension of
5-iodouracil (1; 238 mg, 1.0 mmol) in methylene chloride (15 mL). After
20 minutes of stirring at room temperature, when a clear solution was
obtained, a portion of well-dried 1,2,3,5-tetra-O-benzoyl-2-C-β-methyl-β-d-
ribofuranose (2; 580 mg, 1.0 mmol) and SnCl4 (0.4 mL, ca. 3.4 mmol) were
added, then stirred at room temperature for 24 hours. The reaction mixture
was treated with a cold solution of NaHCO3, the layers were separated,
and aqueous layer was washed with methylene chloride (3 × 50 mL). The
combined organic extracts were dried over Na2SO4 and evaporated to an
oil. The product was purified on a silica gel short column in hexane-ethyl
acetate (2:1) to get 3 as a homogenous by TLC white oily solid. Yield 502
1
mg (72%). H NMR 11.96 (bs, 1H, NH), 8.16 (s, 1H, H6), 7.99–7.34 (m,
15H, Ph), 6.47 (s, 1H, H1ꢁ), 5.75 (d, 1H, H3ꢁ), 4.76–4.70 (m, 3H, H4ꢁ, H5ꢁ),
1.67 (s, 3H, 2ꢁCH3). 13C NMR 165.6, 164.6, 164.5 (3 × PhC O), 160.4 (C4),
=
150.0 (C2), 145.5 (C6), 133.9, 133.6, 129.4, 129.3, 129.1, 128.8, 128.7, 128.6,
128.5 (Ph), 89.4 (C1ꢁ), 84.6 (C4ꢁ), 78.9 (C2ꢁ), 75.4 (C3ꢁ), 70.1 (C5), 63.8
(C5ꢁ), 18.1 (2ꢁCH3). HRMS calcd for [C31H25N2O9I + H]+ m/z 697.0683,
found 697.0650. Anal. (C31H25N2O9I) C, H, N.
5-Iodo-2ꢁ-C-β-methyl-D-uridine (4)
Method A. Compound 3 (69.6 mg, 0.1 mmol) was stirred in 0.1 M
MeONa (4 mL) at room temperature for 24 hours. The solution was then
neutralized with AcOH and evaporated to a solid residue; the crude product
4 was purified on a silica gel short column in CHCl3-MeOH (4:1), then
crystallized from toluene-ethanol, m.p. 205◦C (dec.). Yield 28 mg (73%).
Anal. C,H,N.
Method B. 3 (69.5 mg, 0.1 mmol) was deprotected in saturated
methanolic ammonia (20 mL), room temperature, 24 hours. After

718
P. Januszczyk et al.
evaporation of the solvent the product was purified like in method A. Yield
1
34 mg (90%). H NMR 11.70 (bs, 1H, NH), 8.75 (s, 1H, H6), 5.73 (s, 1H,
H1ꢁ), 5.42 (t, J = 3.3, 1H, 5ꢁOH), 5.18 (d, J = 6.3, 1H, 3ꢁOH), 5.15 (s, 1H,
2ꢁOH), 3.82 (m, 2H, H4ꢁ, H5ꢁa), 3.70 (d, 1H, H3ꢁ), 3.60 (dd, 1H, H5ꢁb),
1.01 (s, 3H, 2ꢁCH3). 13C NMR 160.5 (C4), 150.5 (C2), 144.8 (C6), 91.1
(C1ꢁ), 82.2 (C4ꢁ), 78.4 (C2ꢁ), 70.8 (C3ꢁ), 69.0 (C5),57.9 (C5ꢁ), 19.6 (2ꢁCH3).
HRMS calcd for [C10H13N2O6I + H]+ m/z 384.9897, found 384.9861. Anal.
(C10H13N2O6I) C, H, N.
5-Decyn-1-yl-2ꢁ,3ꢁ,5ꢁ-tri-O-benzoyl-2ꢁ-C-β-methyl-D-uridine (5)
An anhydrous mixture of 3 (696 mg, 1.0 mmol), 1-decyne (0.54 mL,
3.0 mmol), Pd(Ph3P)4 (115 mg, 0.1 mmol), CuI (38 mg, 0.2 mmol) and
triethylamine (0.28 mL, 2.0 mmol) in DMF (10 mL) was stirred under
argon atmosphere, room temperature for 19 hours. After evaporation of
volatiles in vacuo, the residue was chromatographed on silica gel column
using hexane-ethyl acetale (7:3) as an eluent to yield 5 (530 mg, 75%) as
a colorless oil. This material, homogenous by TLC, was used for next steps
1
without further purification. H NMR 11.86 (bs, 1H, NH), 8.01–7.36 (m,
15H, Ph), 7.95 (s, 1H, H6), 6.49 (s, 1H, H1ꢁ), 5.75 (d, 1H, H3ꢁ), 4.77–4.74
(m, 3H, H4ꢁ, H5ꢁ), 2.38 (t, J = 6.3, 2H, αCH2), 1.50 (m, 2H, βCH2), 1.69 (s,
3H, 2ꢁCH3), 1.38–1.25 (m, 10H, 5 × CH2), 0.86 (t, J = 7.2, 3H, CH3). 13C
=
NMR 165.6, 164.6, 164.5 (3 × PhC O), 161.7 (C4), 149.3 (C2), 143.1 (C6),
133.9, 133.6, 129.4, 129.3, 129.2, 128.8, 128.7, 128.6, 128.5 (Ph), 99.5 (C5),
93.9 (C≡C), 89.4 (C1ꢁ), 84.5 (C4ꢁ), 79.0 (C2ꢁ), 75.4 (C3ꢁ), 72.4 (C≡C), 63.9
(C5ꢁ), 31.2 (αCH2), 28.6, 28.5, 28.3, 28.1, 22.1, 18.8 (6 x CH2), 18.1 (2ꢁCH3),
14.0 (CH3).
5-Decyn-1-yl-2ꢁ-C-β-methyl-D-uridine (7)
Compound 5 (353 mg, 0.5 mmol) was stirred in saturated methanolic
ammonia (25 mL), room temperature, for 24 hours. After evaporation of
the solvent the product was purified by short-column silica gel chromatog-
raphy in CHCl3-MeOH (6:1) to obtain the deprotected nucleoside 7 as a
white solid. Yield 189 mg (96%). An analytical sample was crystallized from
1
ethyl acetate, m.p. 145◦C. H NMR 11.61 (s, 1H, NH), 8.44 (s, 1H, H6),
5.71 (s, 1H, H1ꢁ), 5.34 (t, J = 4.2, 1H, 5ꢁOH), 5.19 (d, J = 6.6, 1H, 3ꢁOH),
5.17 (s, 1H, 2ꢁOH), 3.83–3.57 (m, 4H, H3ꢁ, H4ꢁ, H5ꢁ), 2.32 (t, J = 6.9, 2H,
αCH2), 1.45 (m, 2H, βCH2), 1.37–1.25 (m, 10H, 5 x CH2), 0.99 (s, 3H,
2ꢁCH3), 0.85 (t, J = 6.6, 3H, CH3). 13C NMR 161.7 (C4), 149.8 (C2), 142.5
(C6), 98.9 (C5), 93.3 (C≡C), 91.2 (C1ꢁ), 82.2 (C4ꢁ), 78.4 (C2ꢁ), 72.8 (C≡C),
71.1 (C3ꢁ), 58.2 (C5ꢁ), 31.3 (αCH2), 28.6, 28.5, 28.3, 28.2, 22.1, 18.9 (6 ×
CH2), 19.7 (2ꢁCH3), 14.0 (CH3). HRMS calcd for [C20H30N2O6 + H]+ m/z
395.2182, found 395.2191. Anal. (C20H30N2O6) C, H, N.

2ꢁ-C-Methyl Analogues
5-Dodecyn-1-yl-2ꢁ-C-β-methyl-D-uridine (8)
719
Treatment of 3 (279 mg, 0.4 mmol) with 1-dodecyne (80 mg, 0.10 mL,
0.48 mmol) by the method described above for the synthesis of 5 followed
by deblocking of 6 with saturated methanolic ammonia and purification,
as in the case of 7 gave the nucleoside 8 (27.3 mg, total yield 32%), m.p.
135–138◦C. 1H NMR 11.59 (bs, 1H, NH), 8.44 (s, 1H, H6), 5.75 (s, 1H, H1ꢁ),
5.33 (t, J = 4.2, 1H, 5ꢁOH), 5.19 (d, J = 6.3, 1H, 3ꢁOH), 5.16 (s, 1H, 2ꢁOH),
5.16 3.83–3.33 (m, 4H, H3ꢁ, H4ꢁ, H5ꢁ), 2.32 (t, J = 6.6, 2H, αCH2), 1.46
(m, 2H, βCH2), 1.37–1.23 (m, 14H, 7 × CH2), 1.00 (s, 3H, 2ꢁCH3), 0.83
(t, J = 6.9, 3H, CH3). 13C NMR 161.6 (C4), 149.7 (C2), 142.4 (C6), 98.8
(C5), 93.2 (C≡C), 91.2 (C1ꢁ), 82.1 (C4ꢁ), 78.3 (C2ꢁ), 72.8 (C≡C), 71.0 (C3ꢁ),
58.2 (C5ꢁ), 31.3 (αCH2), 29.0 28.9, 28.7, 28.5, 28.3, 28.2, 22.1, 18.8 (8 x
CH2), 19.7 (2ꢁCH3), 14.0 (CH3). HRMS calcd for [C22H34N2O6 + H]+ m/z
423.2520, found 423.2495. Anal. (C22H34N2O6) C, H, N.
3-(2,3,5-Tri-O-benzoyl-2-C-β-methyl-β-D-ribofuranosyl)-6-octyl-
2,3-dihydro-furano[2,3-d]-pyrimidin-2(1H)-one (9)
An anhydrous mixture of 3 (696 mg, 1.0 mmol), 1-decyne (0.22 mL, 1.2
mmol), 10% Pd/C (42 mg) and CuI (10 mg, 0.053 mmol) in triethylamine
(25 mL) and acetonitrile (25 mL) was stirred under argon atmosphere at
80◦C for 5 hours. After this time TLC showed the single fluorescent spot
of product 9. The reaction mixture was filtered, a precipitate was washed
with acetonitrile, and the solvents were removed in vacuo. The product was
purified by silica gel chromatography in hexane-ethyl acetate (3:2), to yield
580 mg (82%) of a homogenous by TLC, colorless oil. This material was
applied for the next step without further purification. 1H NMR 8.52 (s, 1H,
H4), 8.03–7.37 (m, 15H, Ph), 6.79 (s, 1H, H1ꢁ), 6.42 (s, 1H, H5), 5.78 (d,
1H, H3ꢁ), 4.78 (m, 3H, H4ꢁ, H5ꢁ), 2.66 (t, J = 7.2, 2H, αCH2), 1.60 (m,
5H, βCH2, 2ꢁCH3), 1.27 (m, 10H, 5 × CH2), 0.85 (t, J = 7.2, 3H, CH3).
13C NMR 171.8 (C7a) 165.6, 164.7, 164.6 (3 × PhC = O), 159.3 (C6), 153.8
(C2), 138.0 (C4), 133.8, 133.7, 133.5, 129.5, 129.3, 129.2, 128.8, 128.7, 128.6,
128.5 (Ph), 107.3 (C4a), 99.7 (C5), 89.6 (C1ꢁ), 84.9 (C4ꢁ), 79.6 (C2ꢁ), 75.6
(C3ꢁ), 64.1 (C5ꢁ), 31.2 (αCH2), 28.6, 28.5, 28.3, 27.3, 26.3, 22.0 (6 × CH2),
18.3 (2ꢁCH3), 13.9 (CH3).
3-(2,3,5-Tri-O-benzoyl-2-C-β-methyl-β-D-ribofuranosyl)-6-decyl-
2,3-dihydro-furano[2,3-d]-pyrimidin-2(1H)-one (10)
Treatment of 5-iodo derivative 3 (280 mg, 0.40 mmol) with 1-dodecyne
(80 mg; 0.10 mL, 0.48 mmol) by the method described for synthesis of 9,
1
gave nucleoside 10 (372 mg, 51%) as a colorless oil. H NMR 8.52 (s, 1H,
H4), 8.03–7.34 (m, 15H, Ph), 6.80 (s, 1H, H1ꢁ), 6.42 (s, 1H, H5), 5.79 (d,
1H, H3ꢁ), 4.80 (m, 3H, H4ꢁ, H5ꢁ), 2.66 (t, J = 6.6, 2H, αCH2), 1.60 (m, 5H,
βCH2, 2ꢁCH3), 1.26 (m, 14H, 7 x CH2), 0.81 (t, J = 6.2, 3H, CH3). 13C NMR

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P. Januszczyk et al.
=
171.8 (C7a) 165.5, 164.5, 164.6 (3 × PhC O), 159.2 (C6), 153.8 (C2), 138.0
(C4), 133.7, 133.5, 133.5, 129.4, 129.3, 128.7, 128.7, 128.6, 128.5 (Ph), 107.3
(C4a), 99.7 (C5), 89.6 (C1ꢁ), 84.9 (C4ꢁ), 79.2 (C2ꢁ), 75.6 (C3ꢁ), 64.1 (C5ꢁ),
31.2 (αCH2), 28.9, 28.8, 28.7, 28.6, 28.3, 27.3, 26.2, 22.0 (6 × CH2), 18.3
(2ꢁCH3), 13.9 (CH3).
3-(2-C-β-Methyl-β-D-ribofuranosyl)-6-octyl- 2,3-dihydrofurano[2,3-d]-
pyrimidin-2(1H)-one (11)
Compound 9 (353 mg, 0.5 mmol) was stirred in saturated methanolic
ammonia (25 mL), room temperature, for 24 hours. After evaporation of
the solvent the product was purified by short-column silica gel chromatog-
raphy in CHCl3-MeOH (9:1) to get nucleoside 11 as an oil. Yield 187 mg
(95%). An analytical sample was crystallized from methanol/ethyl acetate,
1
m.p. 155◦C. H NMR 8.87 (s, 1H, H4), 6.41 (s, 1H, H5), 6.03 (s, 1H,
H1ꢁ), 5.36 (t, J = 4.8, 1H, 5ꢁOH), 5.24 (s, 1H, 2ꢁOH), 5.14 (d, J = 7.2, 1H,
3ꢁOH), 3.89–3.84 (m, 2H, H3ꢁ, H4ꢁ), 3.74–3.64 (m, 2H, H5ꢁ), 2.64 (t, J =
7.2, 2H, αCH2), 1.61 (m, 2H, βCH2), 1.29–1.24 (m, 10H, 5 × CH2), 0.94 (s,
3H, 2ꢁCH3), 0.85 (t, J = 6.9, 3H, CH3). 13C NMR 171.1 (C7a), 158.7 (C6),
154.3 (C2), 136.9 (C4), 106.6 (C4a), 99.6 (C5), 92.8 (C1ꢁ), 82.9 (C4ꢁ), 78.6
(C2ꢁ), 71.2 (C3ꢁ), 58.7 (C5ꢁ), 31.2 (αCH2), 28.6, 28.5, 28.4, 27.4, 26.3, 22.1
(6 x CH2), 19.7 (2ꢁCH3), 13.9 (CH3). HRMS calcd for [C20H30N2O6 + H]+
m/z 395.2202, found 395.2182. Anal. (C20H30N2O6) C, H, N.
3-(2-C-β-Methyl-β-D-ribofuranosyl)-6-decyl- 2,3-dihydrofurano[2,3-d]-
pyrimidin-2(1H)-one (12)
Treatment of 10 (372 mg, 0.51 mmol) with methanolic ammonia (7 mL)
1
as described above gave 12 (126 mg, 59%) as a white solid foam. H NMR
8.87 (s, 1H, H4), 6.41 (s, 1H, H5), 6.03 (s, 1H, H1ꢁ), 5.36 (t, J = 4.8, 1H,
5ꢁOH), 5.24 (s, 1H, 2ꢁOH), 5.14 (d, J = 7.2, 1H, 3ꢁOH), 3.89–3.84 (m, 2H,
H3ꢁ, H4ꢁ), 3.74–3.64 (m, 2H, H5ꢁ), 2.63 (t, J = 6.9, 2H, αCH2), 1.61 (m,
2H, βCH2), 1.29–1.24 (m, 10H, 5 × CH2), 0.94 (s, 3H, 2ꢁCH3), 0.85 (t, J =
6.2, 3H, CH3). 13C NMR 171.1 (C7a), 158.7 (C6), 154.2 (C2), 136.8 (C4),
106.6 (C4a), 99.6 (C5), 92.8 (C1ꢁ), 82.3 (C4ꢁ), 78.5 (C2ꢁ), 71.2 (C3ꢁ),
58.7 (C5ꢁ), 31.3 (αCH2), 28.9, 28.8, 28.7, 28.6, 28.3, 27.3, 26.2, 22.1 (8 ×
CH2), 19.7 (2ꢁCH3), 13.9 (CH3). HRMS calcd for [C22H34N2O6 + H]+ m/z
423.2522, found 423.2495. Anal. (C22H34N2O6) C, H, N.
4-O-Methyl-5-(2-oxodecyl)-2ꢁ-C-β-methyl-D-uridine (13)
A sample of 9 (353 mg, 0.5 mmol) was stirred in 0.1 M MeONa (20
mL) at room temperature for 24 hours. After this time the reaction mixture
contained two products (TLC). The mixture was neutralized with acetic
acid, methanol was evaporated, and the products were separated on a
silica gel column in chloroform-methanol 9:1. First UV-absorbing fractions

2ꢁ-C-Methyl Analogues
721
contained compound 13 (87 mg of an oil, 41%), and further elution
gave the already known nucleoside 11 (78 mg, 40%). The product 13 was
crystallized from hexane-methanol, m.p. 115◦C. 1H NMR 11.96 (s, 1H, NH),
8.19 (s, 1H, H6), 5.91 (s, 1H, H1ꢁ), 5.22 (t, J = 4.8, 1H, 5ꢁOH), 5.16 (s,
1H, 2ꢁOH), 5.12 (d, J = 7.2, 1H, 3ꢁOH), 3.78 (s, 3H, OCH3), 3.82–3.87
(m, 2H, H3ꢁ, H4ꢁ), 3.68–3.59 (m, 2H, H5ꢁ), 3.40 (s, 2H, C5-CH2), 2.45 (t,
J = 7.5, 2H, αCH2), 1.46 (m, 2H, βCH2), 1.27–1.23 (m, 10H, 5 × CH2),
0.94 (s, 3H, 2ꢁCH3), 0.85 (t, J = 6.9, 3H, CH3). 13C NMR 206.9 (C = O),
169.4 (C4), 154.9 (C2), 142.9 (C6), 101.6 (C5), 91.7 (C1ꢁ), 82.2 (C4ꢁ), 78.4
(C2ꢁ), 71.5 (C3ꢁ), 58.9 (C5ꢁ), 41.4 (C5-CH2), 31.3 (αCH2), 28.8, 28.8, 28,7,
28.6, 28.5, 23.3, 22.1 (7 × CH2), 19.8 (2ꢁCH3), 14.0 (CH3). HRMS calcd
for [C21H34N2O7 + H]+ m/z 427.2451, found 427.2444. Anal. Calc. for
C21H34N2O7 (426.51): C, 59.15; H, 7.98; N, 6.57. Found: C, 58.88; H, 8.32;
N, 6.46.
3-(2-C-β-Methyl-β-D-ribofuranosyl)-6-octyl- 2,3-dihydropyrrolo[2,3-d]-
pyrimidin-2(3H,7H)-one (14)
Method A. A solution of 11 (118.2 mg, 0.3 mmol) in saturated methano-
lic ammonia (50 mL) was placed in a pressure glass tube and heated in an
oil bath at 50◦C for 48 hours. The solvent was evaporated, and the residue
was chromatographed on a silica gel column in chloroform-methanol (4:1)
to give 14 (87 mg, 74%) as a colorless oil. The product was crystallized from
a mixture of hexane, methanol and ethyl acetate, m.p. 155◦C.
Method B. The open-ring compound 13 (85.2 mg, 0.2 mmol) was
treated with methanolic ammonia (20 mL) by method A to give 14 (47.3
mg, 60%), identical in all respects with the product of obtained from 11. 1H
NMR 11.08 (s, 1H, N7H) 8.66 (s, 1H, H4), 6.09 (s, 1H, H1ꢁ), 5.85 (s, 1H, H5),
5.29 (t, J = 3.6, 1H, 5ꢁOH), 5.09 (s, 1H, 2ꢁOH), 5.07 (d, J = 5.4, 1H, 3ꢁOH),
3.88–3.83 (m, 2H, H3ꢁ, H4ꢁ), 3.75–3.67 (m, 2H, H5ꢁ), 2.52 (t, 2H, αCH2),
1.59 (m, 2H, βCH2), 1.27–1.24 (m, 10H, 5 × CH2), 0.89 (s, 3H, 2ꢁ), 0.84
(t, J = 5.1, 3H, CH3). 13C NMR 159.1 (C7a), 154.3 (C2), 142.7 (C6), 134.6
(C4), 108.7 (C4a), 96.2 (C5), 92.3 (C1ꢁ), 82.1 (C4ꢁ), 78.4 (C2ꢁ), 71.4 (C3v),
58.8 (C5ꢁ), 31.3 (αCH2), 28.9, 28.9, 28.8, 28.7, 28.6, 28.5, 27.4, 22.1 (8 ×
CH2), 19.9 (2ꢁCH3), 13.9.0 (CH3). HRMS calcd for [C20H31N3O5 + H]+
m/z 394.2334, found 394.2342. Anal. (C20H31N3O5) C, H, N.
3-(2-C-β-Methyl-β-D-ribofuranosyl)-6-decyl- 2,3-dihydropyrrolo[2,3-d]-
pyrimidin-2(3H,7H)-one (15)
Treatment of 12 (64 mg, 0.15 mmol) with methanolic ammonia (6 mL)
as described above (Method A) gave 15 (30.5 mg, 48%) as a white solid.
11.08 (s, 1H, N7H) 8.66 (s, 1H, H4), 6.09 (s, 1H, H1ꢁ), 5.85 (s, 1H, H5),
5.28 (t, J = 3.6, 1H, 5ꢁOH), 5.10 (s, 1H, 2ꢁOH), 5.08 (d, J = 5.7, 1H,
3ꢁOH), 3.85–3.83 (m, 2H, H3ꢁ, H4ꢁ), 3.73–3.67 (m, 2H, H5ꢁ), 2.53 (t, 2H,

722
P. Januszczyk et al.
αCH2), 1.58 (m, 2H, βCH2), 1.27–1.24 (m, 14H, 7 x CH2), 0.90 (s, J = 5.1,
3H, 2ꢁCH3), 0.85 (t, 3H, CH3). 13C NMR 159.1 (C7a), 154.3 (C2), 142.7
(C6), 134.6 (C4), 108.7 (C4a), 96.2 (C5), 92.3 (C1ꢁ), 82.1 (C4ꢁ), 78.4 (C2ꢁ),
71.4 (C3ꢁ), 58.8 (C5ꢁ), 31.2 (αCH2), 28.7, 28.6, 28.5, 27.8, 27.5, 22.1 (6 ×
CH2), 19.9 (2ꢁCH3), 14.0 (CH3). HRMS calcd for [C22H35N3O5 + H]+ m/z
422.2673, found 422.2655. Anal. (C22H35N3O5) C, H, N.
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