The first synthesis and cytostatic activity of novel 6-(fluoromethyl)purine bases and nucleosides

Article abstract of DOI:10.1039/b508122j

Two alternative approaches to the synthesis of novel 6-(fluoromethyl)purine bases and nucleosides are described either by direct deoxyfluorination or by multistep functional group transformations starting from 6-(hydroxymethyl) purines. 6-(Fluoromethyl)pu

Full text of DOI:10.1039/b508122j

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A R T I C L E
The first synthesis and cytostatic activity of novel
6-(fluoromethyl)purine bases and nucleosides†
ˇ
Peter Silha´r, Radek Pohl, Ivan Votruba and Michal Hocek*
Centre for New Antivirals and Antineoplastics, Institute of Organic Chemistry and Biochemistry,
Academy of Sciences of the Czech Republic, Flemingovo nam. 2, CZ-16610, Prague 6, Czech
Republic. E-mail: hocek@uochb.cas.cz; Fax: +420 220183559; Tel: +420 220183324
Received 8th June 2005, Accepted 9th June 2005
First published as an Advance Article on the web 4th July 2005
Two alternative approaches to the synthesis of novel 6-(fluoromethyl)purine bases and nucleosides are
described either by direct deoxyfluorination or by multistep functional group transformations starting from
6-(hydroxymethyl)purines. 6-(Fluoromethyl)purine ribonucleoside displayed significant cytostatic effects.
Introduction
Results and discussion
Several types of purines bearing C-substituents in the position
6 are biologically active (Chart 1). 6-Aryl and 6-hetarylpurine,1
6-trifluoromethylpurine,2 as well as 6-(hydroxymethyl)purine3
ribonucleosides display significant cytostatic activity. 6-
Methylpurine, as well as its ribonucleoside, are highly cytotoxic4
and its liberation by purine nucleoside phosphorylases from
its non-toxic deoxyribonucleoside was proposed as a novel
principle in the gene therapy of cancer.5 Fluoromethyl is a
simple isosteric derivative of methyl group and fluorine is often
used as surrogate for oxygen in biologically active compounds.
Hydrophobic nucleobase surrogates, including fluorinated and
trifluoromethylated (het)aromatics, are6 very promising tools
in chemical biology (e.g., extension of the genetic alphabet,
etc.). The biological activities and other applications of the
above mentioned important classes of compounds imply that the
missing logical members of the series, 6-(fluoromethyl)purines,
are of great interest both in medicinal chemistry and chemical
biology. Surprisingly, these simple compounds have, to the best
of our knowledge, never been reported.
Recently, we have reported3 a facile and efficient synthesis
of 6-(hydroxymethyl)purines by Pd-catalyzed cross-coupling
reactions of 6-halopurines and (acyloxymethyl)zinc iodides
followed by deprotection. Here, we wish to report the first
synthesis of 6-(fluoromethyl)purines starting from these now
easily available intermediates either by direct deoxyfluorinations
or by multistep procedures. 6-(Hydroxymethyl)purines bases
protected in position 9 or nucleosides protected in the glycon
part were needed for the fluorinations. The protected bases
3a,b were prepared by a previously reported method.3 In
nucleoside derivatives, the procedures and protecting groups
have to be modified in order to enable selective deacylation of
the acyloxymethyl group at the purine in presence of the acyl-
protected sugar part. Therefore, we have used a combination of
(acetyloxymethyl)zinc iodide for cross-coupling reactions and
a more stable toluoyl protecting group for protection of the
nucleosides. The protected (acetyloxymethyl)purine nucleosides
2c,d were obtained in good yields but their deacetylation by
NH3–EtOH was not fully selective and the desired sugar-
protected 6-(hydroxymethyl)purine nucleosides 3c,d were iso-
lated in moderate yields of ca. 30–35% besides a mixture of
partially and fully deprotected nucleosides. Interestingly, an
addition of ZnCl2 (1.2 eq.) significantly enhanced the selectivity
of deacylation to give the key intermediates 3c,d in acceptable
yields of 60 and 69%, respectively and ca. 20% of starting
material was recovered (Scheme 1).
Chart 1 Cytostatic 6-substituted purine ribonucleosides.
There are scarce references to other halomethylpurines. 6-
(Chloromethyl)purine was synthesized in low yield from 6-
methylpurine-N-oxide or by chlorination of 6-methylpurine
with NCS, followed by partial reduction of the inter-
mediate 6-(trichloromethyl)purine.7 Analogously, bromination
of 6-methylpurine with NBS afforded 6-(dibromomethyl)-
and 6-(tribromomethyl)purine that could be partially hydro-
genated to 6-(bromomethyl)purine.7 A multistep synthesis of
6-(iodomethyl)purine ribonucleoside8 was based on Finkelstein
reaction of NaI with 6-(mesyloxymethyl)purine which was pre-
pared via 6-(hydroxymethyl)purine from purine ribonucleoside
by photoaddition of methanol in moderate yield.
Scheme 1
At first we have tried direct deoxyfluorinations of hydrox-
ymethyl group with various commercially available fluorinating
† Electronic supplementary information (ESI) available: NMR spectra
of compounds 4. See http://dx.doi.org/10.1039/b508122j
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 0 0 1 – 3 0 0 7
3 0 0 1
©

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obtained with the use of perfluor-1-butanesulfonyl fluoride10
agents (step A, Scheme 2, Table 1). Thus, deoxyfluorination with
(diethylamino)sulfur trifluoride (DAST)9 gave only low yield
of product 4b (entry 1, Table 1). Slightly better results were
with Hu¨nig’s base in methylene chloride (entries 4, 5; Table 1)
but not with DBU in toluene (entries 2, 3). Next, we tried Deoxo-
Fluor11 ([bis-(2-methoxyethyl)amino]sulfur trifluoride) as a mild
and thermally stable reagent to afford the desired products 4a–
d in better yields of 41–46% (entry 6–9, Table 1). Notably, in
the reactions with perfluorbutanesulfonyl fluoride in presence
of Hu¨nig’s base (but not DBU in toluene) or with Deoxo-Fluor
(1.5 eq.) the unreacted starting alcohol 3a–d was recovered in
the yields of 30–35% and 13–20%, respectively, and re-used.
Therefore even this very simple and straightforward one-step
but rather moderately yielding procedure is relatively efficient.
An alternative way to prepare the desired fluoromethyl deriva-
tives is to perform multi-step sequences, via transformation of
hydroxy groups to a suitable leaving group for nucleophilic
substitutions (Scheme 2). Thus, substitution of mesylates,12
tosylates13 or triflates14 by fluoride proceeded in moderate to
good yields. The mesylates 5a–d were prepared in very good
yields from 3a–d and Ms2O under standard conditions (step
B). Unfortunately, in our hands a substitution of mesyloxy
group in derivatives 5a,b by fluoride anion from Et3N·3HF
(step C, Scheme 2) proceeded with low yields (entries 14,
15; Table 1). Therefore we have turned our efforts to 6-
(iodomethyl)purines. These intermediates were prepared either
by direct deoxyiodination of hydroxymethylpurines 3 or by
Finkelstein15 reaction of mesylates 5. Model deoxyiodination
of 6-(hydroxymethyl)purines 3a,b (step E, Scheme 2) by the
16
use of I2 and PPh3 proceeded in acceptable yields of 68 and
79%, respectively. On the other hand the Finkelstein reactions
of mesylates 5a–d (step D, entries 16–19, Table 1) gave the
iodomethyl derivatives 6a–d in nearly quantitative yields. The
total yields of the two-step and direct iodination are comparable.
The direct method is shorter but in the two-step sequence the
isolation of products is more convenient. The final nucleophilic
substitution of the iodo derivatives was acomplished by making
use of AgF17 (step F). It was very efficient because of the
higher insolubility of the resulting AgI than the starting AgF
in THF. The reactions gave the desired 6-(fluromethyl)purines
4a–d in very good yields of 72–84%. In comparison, the multistep
Scheme 2 Yields of the particular steps are given in Table 1. A:
(i) DAST, CH2Cl2; (ii) C4F9SO2F, DBU, toluene; (iii) C4F9SO2F, iPr2EtN,
CH2Cl2 or (iv) Deoxo-Fluor, CH2Cl2. B: Ms2O, iPr2EtN·CH2Cl2,
DMAP (cat.), 2 h. C: Et3N·3HF, Pr2EtN, DCE, 80 ◦C, 12 h. D: NaI,
i
acetone, rt, 1.5 h. E: I2, PPh3, THF or CH2Cl2, rt, 30 min. F AgF,
THF, rt, 10 h G Dowex 50WX8 (H+), EtOH, 70 ◦C, 1.5 h. H: NaOMe
(0.2 eq), MeOH, rt.
Table 1 Yields of the particular steps of the synthesis
Entry
Step
Starting compound
Product
Reagent
Yield (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
A (i)
A (ii)
A (ii)
A (iii)
A (iii)
A (iv)
A (iv)a
A (iv)
A (iv)
B
B
B
B
C
C
D
D
D
D
E
E
F
3b
3a
3b
3a
3b
3a
3b
3c
3d
3a
3b
3c
3d
5a
5b
5a
5b
5c
5d
3a
3b
6a
6b
6c
6d
4b
4c
4d
4b
4a
4b
4a
4b
4a
4b
4c
4d
5a
5b
5c
5d
4a
4b
6a
6b
6c
6d
6a
6b
4a
4b
4c
4d
4e
4f
DAST
18
13
13
31
23
42
46
41
43
93
96
90
C4F9SO2F
C4F9SO2F
C4F9SO2F
C4F9SO2F
Deoxo-Fluor
Deoxo-Fluor
Deoxo-Fluor
Deoxo-Fluor
Ms2O
Ms2O
Ms2O
Ms2O
Et3N·HF
Et3N·HF
NaI
NaI
NaI
95
18 (17)
14 (13)
95 (88)
95 (91)
98 (88)
94 (89)
68
NaI
I2–PPh3
I2–PPh3
AgF
AgF
AgF
79
77 (68)
72 (66)
84 (74)
81 (72)
70
82
79
F
F
F
G
H
H
AgF
H+–EtOH
MeONa
MeONa
4g
a In the presence of iPr2EtN. b Values in parentheses are overall yields from 3a–d.
3 0 0 2
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 0 0 1 – 3 0 0 7

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Table 2 Cytostatic and ADA inhibitory activity of title compounds
IC50/lmol l−1a
All preparations of (acyloxymethyl)zinc iodides and cross-
coupling reactions were conducted under argon atmosphere.
THF was dried and distilled from sodium–benzophenone.
NMR spectra were recorded on Bruker Avance 400 MHz
spectrometer (1H at 400, 13C at 100.6 MHz), a Bruker
Compound
HL60
CCRF-CEM
ADA
1
Avance (500 MHz for H and 125.8 MHz for 13C). Chemical
4a
4e
4f
NAb
NA
1.54 ( 0.11)
NA
NA
NA
0.70 ( 0.04)
NA
NA
NA
NA
NA
shifts (in ppm, d scale) were referenced to TMS as internal
standard. For spectra, refer to the supplementary information.
The assignment of carbons was based on C,H-HSQC and
C,H-HMBC experiments. Melting points were determined
on a Kofler block and are uncorrected. Optical rotations
were measured at 25 ◦C on a Autopol IV (Rudolph Research
Analytical) polarimeter, [a]D values are given in 10−1 deg cm2 g−1.
Mass spectra were measured on a ZAB-EQ (VG Analytical)
spectrometer using FAB (ionization by Xe, accelerating voltage
8 kV, glycerol matrix). Cytostatic activity tests were performed
as described in ref.1a ADA inhibition assay was performed by
standard technique ref.20
4g
a Values are means of four experiments, standard deviation is given in
parentheses. b NA = not active (inhibition of cell growth at 10 lM was
lower than 30%).
sequence via iodomethyl derivatives gives the fluoromethyl-
purines 4a–d in relatively good total yields of 66–74% from
3a–d. On the other hand the direct deoxyfluorinations offers
somewhat lower yields (41–46%) but saves 1–2 steps.
Standard deprotection of 6-(fluoromethyl)purine inter-
mediates 4b–d was used to prepare the final free 6-
(fluoromethyl)purine base and nucleosides 4e–g (Scheme 2,
entries 26–28, Table 1). The THP protective group in position 9
of purine is easily cleavable under mild acidic conditions. Thus
compound 4b was deprotected using Dowex 50 × 8 (H+ form)18
in ethanol to afford free base 4e in 70% of yield. The ester groups
in 4c,d were cleaved by NaOMe in methanol at rt19 to give free
nucleosides 4f,g in about 80% yield.
Title 6-(fluoromethyl)purines and nucleosides 4a,e–g, were
subjected for biological activity screening. In vitro cytostatic
activity tests (inhibition of cell growth) were performed using
the following cell cultures: mouse leukemia L1210 cells (ATCC
CCL 219); human promyelocytic leukemia HL60 cells (ATCC
CCL 240); human cervix carcinoma HeLa S3 cells (ATCC
CCL 2.2); and human T lymphoblastoid CCRF-CEM cell
line (ATCC CCL 119). Adenosine deaminase (ADA) inhibition
was studied20 on calf intestinal adenosine aminohydrolase (EC
3.5.4.4.). The results are summarized in Table 2.
6-Chloro-9-(2,3,5-O-toluoyl-b-D-ribofuranosyl)purine
(1c).
New compound prepared in analogy to published method.22
Anal. calcd for C34H29ClN4O7: C, 63.70; H, 4.56; Cl, 5.53; N,
8.74; found: C, 63.61; H, 4.45; Cl, 5.54; N, 8.63. 1H NMR
(400 MHz, CDCl3): 2.38 and 2.42 (2 × s, 9H, CH3-Tol); 4.65
(dd, 1H, Jgem = 12.3, J5 b,4 = 4.0, H-5ꢀb); 4.83 (ddd, 1H, J4 ,3
=
ꢀ
ꢀ
ꢀ ꢀ
4.7, J4 ,5 = 4.0, 3.1, H-4ꢀ); 4.92 (dd, 1H, Jgem = 12.3, J5 a,4
=
ꢀ
ꢀ
ꢀ
ꢀ
3.1, H-5ꢀa); 6.20 (dd, 1H, J3 ,2 = 5.8, J3 ,4 = 4.7, H-3ꢀ); 6.37
ꢀ
ꢀ
ꢀ ꢀ
(t, 1H, J2 ,3 = 5.8, J2 ,1 = 5.3, H-2ꢀ); 6.45 (d, 1H, J1 ,2 = 5.3,
H-1ꢀ); 7.16, 7.23 and 7.25 (3 × m, 3 × 2H, H-m-Tol); 7.80, 7.91
and 7.96 (3 × m, 3 × 2H, H-o-Tol); 8.27 (s, 1H, H-8); 8.62
(s, 1H, H-2). 13C NMR (100.6 MHz, CDCl3): 21.70 and 21.74
(CH3-Tol); 63.15 (CH2-5ꢀ); 71.31 (CH-3ꢀ); 73.73 (CH-2ꢀ); 81.23
(CH-4ꢀ); 87.33 (CH-1ꢀ); 125.50, 125.92 and 126.45 (C-i-Tol);
129.25, 129.29 and 129.35 (CH-m-Tol); 129.70 and 129.86
(CH-o-Tol); 132.30 (C-5); 143.84 (CH-8); 144.34, 144.66 and
144.80 (C-p-Tol); 151.32 (C-4); 151.53 (C-6); 152.28 (CH-2);
165.15, 165.36 and 166.12 (CO-Tol).
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
The only active compound of this series was the 6-
(fluoromethyl)purine ribonucleoside (4f) that exerted signifi-
cant antiproliferative activity against HL-60 and CCRF-CEM
(IC50 = 1.54 and 0.70 lmol l−1, respectively) but no consid-
erable effect against L1210 and HeLa S3 cell-lines. The other
tested compounds were entirely inactive. The cytostatic effect
of 4f is somewhat lower than that of the corresponding 6-
(hydroxymethyl)purine ribonucleoside3 and is comparable to
that of 6-(trifluoromethyl)purine ribonucleoside.2 Unlike the 6-
(hydroxymethyl)purine ribonucleoside3 compound 4f does not
inhibit ADA. Therefore it can be concluded that in terms of
their biological activity the 6-(fluoromethyl)purine nucleosides
are analogues of 6-methylpurine4 nucleosides.
In conclusion, two alternative approaches to the synthesis
of novel 6-(fluoromethyl)purine bases and nucleosides either
by direct deoxyfluorination or by multistep functional group
transformation of 6-(hydroxymethyl)purines have been devel-
oped. The multistep sequence gives higher total yields, while the
direct approach obviously saves time. Ribonucleoside 4f shows
promising cytostatic effects which invite further research in this
field. Application of this methodology to the synthesis of series
of modified nucleoside and nucleotide analogues, their biological
activity screening and DNA polymerase assays are underway.
This methodology may also be adopted for the synthesis of other
types of fluoromethyl(het)aromatics as hydrophobic nucleobase
surrogates.
Preparation of (acetyloxymethyl)zinc iodide
A solution of iodomethyl acetate23 (2.00 g, 10 mmol) in THF
(5 ml) was added at 0–5 ◦C to the suspension of zinc dust
(1.31 g, 20 mmol) in THF (4 ml), which was preactivated
with dibromoethane (20 ll) and trimethylsilyl chloride (20 ll).
Reaction mixture was stirred 1 h at 0–5 ◦C. After settling down
of non-reacted zinc, a clear solution was obtained. The con-
centration of (acetyloxymethyl)zinc iodide has been determined
by complexometric titration of Zn(II) ions in hydrolyzed aliquot
(average value approx. 1.0 mmol ml−1).
General procedure for cross-couplings of (acetyloxymethyl)zinc
iodide with 6-chloropurine nucleosides 1c,d
A solution of (acetyloxymethyl)zinc iodide (1.7 ml, ca. 1.5 mmol)
in THF was added at rt to a solution of a 6-chloropurine
nucleoside (1c or 1d, 0.5 mmol), Pd(PPh3)4 (29 mg, 5%) in THF
(1 ml) and stirred at rt for 8 h. The reaction was quenched with
1 M NaH2PO4 (30 ml) and extracted with CHCl3 (3 × 30 ml).
Collected organic phases were dried over MgSO4, filtered and
the solvent was evaporated. The crude oily product was purified
on silica gel (hexanes–ethyl acetate 3 : 1–1 : 1).
6-(Acetyloxymethyl)-9-(2,3,5-tri-O-toluoyl-b-D-ribofuranosyl)-
purine (2c). Yield: 81% as white foam. Exact mass (FAB HR
MS) found: 679.2415; calcd for C37H35N4O9: 679.2404. FAB
MS m/z (%): 679 (MH+, 1); 487 (10); 193 (4); 151 (5); 119
(100). 1H NMR (400 MHz, CDCl3): 2.21 (s, 3H, CH3-Ac);
2.38 and 2.42 (2 × s, 9H,CH3-Tol); 4.66 (dd, 1H, Jgem = 12.2,
Experimental
General
J5 b,4 = 4.1, H-5ꢀb); 4.82 (td, 1H, J4 ,3 = 4.6, J4 ,5 = 4.1, 3.1,
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
Starting materials: 9-benzyl-6-(hydroxymethyl)purine,3 6-
(hydroxymethyl)-9-(tetrahydropyran-2-yl)purine,3 6-chloro-9-
(2-deoxy-3,5-di-O-toluoyl-b-D-erythro-pentofuranosyl)purine.21
H-4); 4.89 (dd, 1H, Jgem = 12.2, J5 a,4 = 3.1, H-5ꢀa); 5.60 (s,
ꢀ
ꢀ
2H, O–CH2); 6.20 (dd, 1H, J3 ,2 = 5.8, J3 ,4 = 4.6, H-3ꢀ); 6.38
ꢀ
ꢀ
ꢀ ꢀ
(t, 1H, J2 ,3 = 5.8, J2 ,1 = 5.5, H-2ꢀ); 6.48 (d, 1H, J1 ,2 = 5.5,
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 0 0 1 – 3 0 0 7
3 0 0 3

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H-1ꢀ); 7.16, 7.22 and 7.26 (3 × m, 3 × 2H, H-m-Tol); 7.81, 7.91
and 7.99 (3 × m, 3 × 2H, H-o-Tol); 8.23 (s, 1H, H-8); 8.85 (s,
1H, H-2). 13C NMR (100.6 MHz, CDCl3): 20.80 (CH3-Ac);
21.70 and 21.73 (CH3-Tol); 62.42 (O-CH2); 63.41 (CH2-5ꢀ);
71.39 (CH-3ꢀ); 73.66 (CH-2ꢀ); 81.06 (CH-4ꢀ); 86.84 (CH-1ꢀ);
125.60, 125.99 and 126.56 (C-i-Tol); 129.22, 129.26 and 129.34
(CH-m-Tol); 129.77, 129.86 and 129.88 (CH-o-Tol); 132.35
(C-5); 143.41 (CH-8); 144.24, 144.59 and 144.71 (C-p-Tol);
151.27 (C-4); 152.65 (CH-2); 155.69 (C-6); 165.15, 165.37 and
166.18(CO-Tol); 170.74 (CO-Ac). IR (CCl4): m = 3039, 1755,
1733, 1612, 1598, 1498, 1410, 1377, 1334, 1266, 1226, 1179,
1125, 1113, 1092, 1021, 643 cm−1.
6.4, J2 b3 = 3.1, H-2ꢀb); 3.46 (ddd, 1H, Jgem = 14.3, J2 a1 = 7.4,
ꢀ
ꢀ
ꢀ
ꢀ
J2 a3 = 6.7, H-2ꢀa); 4.58–4.66 (m, 2H, H-5ꢀb and H-4ꢀ); 4.77
ꢀ
ꢀ
(m, 1H, H-5ꢀa); 5.02 (d, 1H, Jgem = 15.0, O-CH2b); 5.06 (d,
ꢀ
ꢀ
ꢀ ꢀ
1H, Jgem = 15.0, O–CH2a); 5.93 (dt, 1H, J3 2 b = 6.7, J3 2 a
=
3.1, J3 4 = 2.8, H-3ꢀ); 6.60 (dd, 1H, J1 2 a = 7.4, J1 2 b = 6.4,
H-1ꢀ); 7.21 and 7.32 (2 × m, 2 × 2H, H-m-Tol); 7.82 and 7.98
(2 × m, 2 × 2H, H-o-Tol); 8.57 (s, 1H, H-8); 8.78 (s, 1H, H-2).
13C NMR (100.6 MHz, MeOD): 21.62 and 21.67 (CH3-Tol);
37.61 (CH2-2ꢀ); 61.46 (O-CH2); 65.00 (CH2-5ꢀ); 76.46 (CH-3ꢀ);
84.32 (CH-4ꢀ); 86.83 (CH-1ꢀ); 128.08 and 128.14 (C-i-Tol);
130.22 and 130.35 (CH-m-Tol); 130.67 and 130.83 (CH-o-Tol);
132.71 (C-5); 145.49 and 145.82 (C-p-Tol); 146.13 (CH-8);
152.01 (C-4); 153.20 (CH-2); 160.82 (C-6); 167.43 and 167.64
(CO-Tol). IR (CHCl3): m = 3458, 1721, 1612, 1603, 1585, 1495,
1410, 1336, 1269, 1179, 1121, 1102, 1020, 691, 646 cm−1.
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
6-(Acetyloxymethyl)-9-(2-deoxy-3,5-di-O-toluoyl-b-D-erythro-
pentofuranosyl)purine (2d). Yield: 77% as white crystals (mp
111–112 ◦C). Anal. calcd for C29H28N4O7: C, 63.96; H, 5.18; N,
10.29; found: C, 63.99; H, 5.18; N, 10.15. FAB MS m/z (%):
Typical procedure for deoxyfluorinations with DAST and
Deoxo-Fluor (step A)
1
545 (M+, 2), 353 (2), 193 (40), 151 (29), 119 (100), 91 (40). H
NMR (400 MHz, CDCl3): 2.22 (s, 3H, CH3-Ac); 2.41 and 2.45
ꢀ
ꢀ
(2 × s, 2 × 3H, CH3-Tol); 2.86 (ddd, 1H, Jgem = 14.1, J2 b,1
=
6-(Hydroxymethyl)purine 3 (0.5 mmol) was dissolved in CH2Cl2
(5 ml) under Ar atmosphere and cooled to −20 ◦C. Deoxo-Fluor
(0.5–1 mmol) was then added and the reaction mixture was al-
lowed to warm to rt and stirred for 10 h. Reaction was quenched
with 5% NaHCO3 and extracted with CHCl3. Organic phase
was drying over MgSO4 concetrated and chromatographed on
silica gel (hexanes–ethyl acetate 2 : 1 to 1: 1).
5.8, J2 b,3 = 2.1, H-2ꢀb); 3.18 (ddd, 1H, Jgem = 14.2, J2 a,1 = 8.4,
ꢀ
ꢀ
ꢀ
ꢀ
J2 a,3 = 6.3, H-2ꢀa); 4.63–4.70 (m, 2H, H-5ꢀb and H-4ꢀ); 4.78
ꢀ
ꢀ
(dd, 1H, Jgem = 13.2, J5 a,4 = 5.2, H-5ꢀa); 5.61 (s, 2H, O-CH2);
ꢀ
ꢀ
5.83 (dt, 1H, J3 ,2 a = 6.3, J3 ,4 = 2.2, J3 ,2 b = 2.1, H-3ꢀ); 6.60 (dd,
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
1H, J1 ,2 a = 8.4, J1 ,2 b = 5.8, H-1ꢀ); 7.23 and 7.29 (2 × m, 2 ×
2H, H-m-Tol); 7.90 and 7.98 (2 × m, 2 × 2H, H-o-Tol); 8.25 (s,
1H, H-8); 8.89 (s, 1H, H-2). 13C NMR (100.6 MHz, CDCl3):
20.78 (CH3-Ac); 21.69 and 21.75 (CH3-Tol); 37.78 (CH2-2ꢀ);
62.43 (O–CH2); 63.89 (CH2-5ꢀ); 75.02 (CH-3ꢀ); 83.14 (CH-4ꢀ);
84.92 (CH-1ꢀ); 126.32 and 126.59 (C-i-Tol); 129.26 (CH-m-Tol);
129.61 and 129.79 (CH-o-Tol); 132.29 (C-5); 143.00 (CH-8);
144.17 and 144.55 (C-p-Tol); 151.03 (C-4); 152.38 (CH-2);
155.54 (C-6); 165.90 and 166.11 (CO-Tol); 170.75 (CO-Ac). IR
(CCl4): m = 3039, 1755, 1728, 1613, 1597, 1496, 1409, 1376,
1333, 1267, 1226, 1178, 1100, 1021 cm−1.
ꢀ
ꢀ
ꢀ ꢀ
Typical procedure for deoxyfluorinations with
perfluorbutane-1-sulfonyl fluoride (step A)
Perfluorobutane-1-sulfonyl fluoride (0,75–1 mmol) was added to
a solution of 6-(hydroxymethyl)purine 3 (0.5 mmol) in toluene
i
or CH2Cl2 (4 ml) in presence of base (DBU or Pr2NEt; 0,83–
1,1 mmol). The reaction mixture was stirred for 12–32 h.
Reaction was quenched with 5% NaHCO3 and extracted with
CHCl3. Organic phases were dried over MgSO4 concentrated
and chromatographed on silica gel (hexanes–ethyl acetate 2 : 1
to 1 : 1).
General procedure for deacetylation of nucleosides 2c,d
Aqueous ammonia (25%, 0.4 ml, 6 mmol) was added to the
mixture of 6-(acetyloxymethyl)purine nucleoside 2 (1 mmol)
and ZnCl2 (164 mg, 1.2 mmol) in EtOH (25 ml). Reaction
mixture was stirred for 12–20 h at rt, adsorbed on silica gel
and chromatographed (hexanes–ethyl acetate 1 : 1–1 : 2).
Typical procedure for reactions of
6-(methanesulfonyloxymethyl)purines 5 with Et3N·3HF (step C)
Hu¨nig’s base (iPr2EtN; 188 ll, 1.1 mmol) and Et3N.3HF (82 ll,
0.5 mmol) were added to a solution of 6-(methanesulfonyl-
oxymethyl)purine 5 (0.5 mmol) in 1,2-dichlorethane (10 ml).
Reaction mixture was stirred for 12–20 h at 80 ◦C. After
starting material was consumed, the reaction mixture was
chromatographed on a column of silica gel (hexanes–ethyl
acetate 1 : 1).
6-(Hydroxymethyl)-9-(2,3,5-tri-O-toluoyl-b-D-ribofuranosyl)-
purine (3c). Yield: 60% as white solid. Exact mass (FAB HR
MS) found: 673.2313; calcd for C35H33N4O8: 673.2298. FAB
1
MS m/z (%): 637 (MH+, 4); 487 (5); 151 (4); 119 (100). H
NMR (500 MHz, DMSO-d6): 2.34, 2.38 and 2.39 (3 × s, 3 ×
3H,CH3-Tol); 4.63 (dd, 1H, Jgem = 12.3, J5 b,4 = 4.8, H-5ꢀb); 4.78
ꢀ
ꢀ
(dd, 1H, Jgem = 12.3, J5 a,4 = 3.6, H-5ꢀa); 4.85 (ddd, 1H, J4 ,3
=
ꢀ
ꢀ
ꢀ ꢀ
Typical procedure for reactions of 6-(iodomethyl)purines 6 with
AgF (step F)
ꢀ
ꢀ
5.7, J4 ,5 = 4.8, 3.6, H-4); 4.89 (d, 2H, JCH2,OH = 6.3, CH2–OH);
ꢀ
ꢀ
ꢀ ꢀ
5.46 (t, 1H, JOH,CH2 = 6.3, OH); 6.23 (dd, 1H, J3 ,2 = 6.0, J3 ,4
=
5.7, H-3ꢀ); 6.51 (dd, 1H, J2 ,3 = 6.0, J2 ,1 = 4.7, H-2ꢀ); 6.66 (d,
A solution of a 6-(iodomethyl)purine 6 (0.2 mmol) in THF (5 ml)
was stirred with AgF (33 mg, 0.26 mmol) for 10 h at rt with
exclusion of light. After the reaction was complete, the solids
were filtered off and washed with ethyl acetate. Volatiles were
evaporated in vacuo and crude product was chromatographed
on silica gel (hexanes–ethyl acetate 2 : 1–1 : 1).
ꢀ
ꢀ
ꢀ ꢀ
1H, J1 ,2 = 4.7, H-1ꢀ); 7.25, 7.30 and 7.31 (3 × m, 3 × 2H,
H-m-Tol); 7.76, 7.85 and 7.87 (3 × m, 3 × 2H, H-o-Tol); 8.76 (s,
1H, H-2); 8.79 (s, 1H, H-8). 13C NMR (125.8 MHz, DMSO-d6):
21.36, 21.37 and 21.39 (CH3-Tol); 60.14 (CH2-OH); 63.19
(CH2-5ꢀ); 70.76 (CH-3ꢀ); 72.91 (CH-2ꢀ); 79.59 (CH-4ꢀ); 86.75
(CH-1ꢀ); 125.75, 126.07 and 126.72 (C-i-Tol); 129.45, 129.52,
129.60 and 129.62 (CH-Tol); 131.81 (C-5); 144.06, 144.57 and
144.69 (C-p-Tol); 145.59 (CH-8); 150.61 (C-4); 152.07 (CH-2);
160.36 (C-6); 164.66, 164.86 and 165.59(CO-Tol). IR (CCl4): m =
3445, 1727, 1612, 1588, 1498, 1412, 1336, 1267, 1180, 1126,
1114, 1093, 691, 645 cm−1.
ꢀ
ꢀ
9-Benzyl-6-(fluoromethyl)purine (4a). Yield: 42% with
Deoxo-Fluor (step A), 68% via 6-(iodomethyl)purine 6a (steps B,
D, F). White crystals, mp 64–65 ◦C. Anal. calcd for C13H11FN4:
C, 64.45; H, 4.58; F, 7.84; N, 23.13; found: C, 64.08; H, 4.60;
F, 7.77; N, 22.68. Exact mass (FAB HR MS) found: 243.1038;
calcd for C13H12FN4: 243.1046. FAB MS m/z (%): 243.1 (MH+,
22); 225 (7); 91 (100). 1H NMR (500 MHz, CDCl3): 5.48 (s, 2H,
CH2-Ph); 5.90 (d, 2H, JH,F = 46.7, CH2-F); 7.30–7.40 (m, 5H,
Ph); 8.10 (s, 1H, H-8); 9.04 (d, 1H, JH,F = 0.8, H-2). 13C NMR
(125.8 MHz, CDCl3): 47.41 (CH2-Ph); 80.97 (d, JC,F = 172, CH2-
F); 127.88, 128.75 and 129.22 (CH-Ph); 131.41 (C-5); 134.82
(C-i-Ph); 145.01 (CH-8); 152.02 (C-4); 152.61 (CH-2); 154.52
6-(Hydroxymethyl)-9-(2-deoxy-3,5-di-O-toluoyl-b-D-erythro-
pentofuranosyl)purine (3d). Yield: 69% as white solid. Exact
mass (FAB HR MS) found: 503.1906; calcd for C27H27N4O6:
503.1931. FAB MS m/z (%): 503 (MH+, 60), 353 (10), 151
1
(100), 119 (90). H NMR (400 MHz, MeOD): 2.38 and 2.42
ꢀ
ꢀ
(2 × s, 2 × 3H, CH3-Tol); 2.88 (ddd, 1H, Jgem = 14.3, J2 b1
=
3 0 0 4
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 0 0 1 – 3 0 0 7

View Online
(d, JC,F = 18, C-6). 19F NMR (188.2 MHz, CDCl3): −225.38 (t,
JF,H = 46.7). IR (CCl4): m = 3035, 1599, 1500, 1407, 1331, 1211,
1030 cm−1.
the reaction mixture was filtered and Dowex was washed with
NH3–EtOH. Volatiles were evaporated in vacuo. Crude product
was chromatographed on silica gel (hexanes–ethyl acetate 1 :
2–0 : 1) and crystallized from ethyl acetate–hexanes to afford
42 mg (70%) of white solid (mp 204–205 ◦C). Anal. calcd for
C6H5FN4: C, 47.37; H, 3.31; F, 12.49; N, 36.83; found: C, 47.02;
H, 3.29; F, 12.59; N, 36.48. FAB MS m/z (%): 153 (MH+, 100);
134 (37); 121 (8). 1H NMR (400 MHz, CDCl3): 5.85 (d, 2H, JH,F
= 46.6, CH2-F); 8.59 (s, 1H, H-8); 8.92 (d, 1H, JH,F = 1.0, H-2).
13C NMR (100.6 MHz, CDCl3): 82.80 (d, JC,F = 169, CH2-F);
127.14 (C-5); 148.09 (CH-8); 153.06 (CH-2); 153.29 (C-6);
6-(Fluoromethyl)-9-(tetrahydropyran-2-yl)purine (4b). Yield:
46% with Deoxo-Fluor (step A), 66% via 6-(iodomethyl)purine
6b (steps B, D, F). White crystals, mp 71–72 ◦C. Exact mass (FAB
HR MS) found: 237.1146; calcd for C11H14FN4O: 237.1152.
1
FAB MS m/z (%): 236 (M+, 11); 149 (33); 85 (100). H NMR
(500 MHz, CDCl3): 1.65–1.87 and 2.04–2.21 (m, 6H, CH2-THP);
3.81 (dt, 1H, J = 11.8 and 2.6, bCH2-O-THP); 4.20 (ddt, 1H,
J = 11.8, 4.5 and 1.7, aCH2-O-THP); 5.83 (dd, 1H, J = 10.4
158.22 (C-4). 19F NMR (188.2 MHz, CDCl3): − 223.82 (t, JF,H
795, 644 cm−1.
=
and 2.5, CH-O-THP); 5.88 and 5.91 (dd, 1H, JH,F = 46.7, Jgem
=
46.6). IR (KBr): m = 3100, 1601, 1479, 1440, 1397, 1328, 1107,
12.6, CH2-F); 8.34 (s, 1H, H-8); 9.00 (s, 1H, H-2). 13C NMR
(125.8 MHz, CDCl3): 22.68, 24.79 and 31.81 (CH2-THP); 68.87
(CH2-O-THP); 80.89 (d, JC,F = 172, CH2-F); 82.09 (CH-O-
THP); 131.57 (C-5); 143.04 (CH-8); 151.14 (C-4); 152.39 (CH-2);
154.47 (d, JC,F = 18, C-6). IR (CCl4): m = 2949, 2857, 1601, 1588,
1496, 1410, 1332, 1210, 1088, 1047, 645 cm−1.
6-(Fluoromethyl)-9-(b-D-ribofuranosyl)purine
(4f).
A
methanolic solution of MeONa (c = 1 M; 35 ll, 0,035
mmol) was added to a solution of 6-(fluoromethyl)purine
ribonucleoside 4c (110 mg, 0,172 mmol) in methanol (10 ml).
After a complete deprotection of starting material (16 h,
monitoring by TLC), the reaction mixture was adsorbed on
silica gel and chromatographed (ethyl acetate–methanol 1 :
0–9 : 1) to give 40 mg (82%) of white solid (crystalization from
6-(Fluoromethyl)-9-(2,3,5-tri-O-toluoyl-b-D-ribofuranosyl)-
purine (4c). Yield: 41% with Deoxo-Fluor (step A), 70% via
6-(iodomethyl)purine 6c (steps B, D, F). White foam. Exact
mass (FAB HR MS) found: 639.2228; calcd for C35H32FN4O7:
639.2255. FAB MS m/z (%): 639 (M+, 2); 621 (2); 487 (10);
◦
MeOH–EtOAc–heptane, mp 184–185 C). [a]2D0 = −29.5 (c =
1
119 (100). H NMR (400 MHz, CDCl3): 2.38, 2.42 and 2.43
3.59, MeOH). Anal. calcd for C11H13FN4O4: C, 46.48; H,
4.61; F, 6.68; N, 19.71; found: C, 46.22; H, 4.45; F, 7.03; N,
19.46. Exact mass (FAB HR MS) found: 285.1002; calcd for
C11H14FN4O4: 285.0999. FAB MS m/z (%): 285 (MH+, 15); 257
ꢀ
ꢀ
(3 × s, 3 × 3H, CH3-Tol); 4.66 (dd, 1H, Jgem = 12.3, J5 b,4
=
4.1, H-5ꢀb); 4.83 (td, 1H, J4 ,3 = 4.6, J4 ,5 = 4.1, 3.1, H-4); 4.91
ꢀ
ꢀ
ꢀ ꢀ
(dd, 1H, Jgem = 12.3, J5 a,4 = 3.1, H-5ꢀa); 5.86 (d, 2H, JH,F
=
ꢀ
ꢀ
46.6, CH2-F); 6.22 (dd, 1H, J3 ,2 = 5.8, J3 ,4 = 4.6, H-3ꢀ); 6.40
ꢀ
ꢀ
ꢀ ꢀ
1
(3); 153 (16). H NMR (400 MHz, DMSO-d6): 3.58 (ddd, 1H,
(t, 1H, J2 ,3 = 5.8, J2 ,1 = 5.4, H-2ꢀ); 6.49 (d, 1H, J1 ,2 = 5.4,
H-1ꢀ); 7.16, 7.23 and 7.26 (3 × m, 3 × 2H, H-m-Tol); 7.81,
7.92 and 7.98 (3 × m, 3 × 2H, H-o-Tol); 8.27 (s, 1H, H-8);
8.88 (s, 1H, H-2). 13C NMR (100.6 MHz, CDCl3): 21.71 and
21.75 (CH3-Tol); 63.30 (CH2-5ꢀ); 71.37 (CH-3ꢀ); 73.68 (CH-2ꢀ);
80.79 (d, JC,F = 173, CH2-F); 81.11 (CH-4ꢀ); 87.00 (CH-1ꢀ);
125.57, 125.98 and 126.52 (C-i-Tol); 129.24, 129.29 and 129.35
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
Jgem = 12.0, J5 b,OH = 5.9, J5 b,4 = 4.1, H-5ꢀb); 3.70 (dt, 1H, Jgem
=
ꢀ
ꢀ
ꢀ
12.0, J5 a,OH = 5.2, J5 a,4 = 4.1, H-5ꢀa); 3.99 (q, 1H, J4 ,5 = 4.1,
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
J4 ,3 = 3.8, H-4ꢀ); 4.20 (bq, 1H, J3 ,2 = 5.1, J3 ,OH = 5.0, J3 ,4
=
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
3.8, H-3ꢀ); 4.63 (q, 1H, J2 ,OH = 5.7, J2 ,1 = 5.6, J2 ,3 = 5.1, H-2ꢀ);
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
5.10 (t, 1H, JOH,5 = 5.9, 5.2, OH-5ꢀ); 5.26 (d, 1H, JOH,3 = 5.0,
ꢀ
ꢀ
OH-3ꢀ); 5.56 (d, 1H, JOH,2 = 5.7, OH-2ꢀ); 5.84 (d, 2H, JH,F
=
ꢀ
46.6, CH2-F); 6.07 (d, 1H, J1 2 = 5.6, H-1ꢀ); 8.90 (s, 1H, H-8);
8.99 (s, 1H, H-2). 13C NMR (100.6 MHz, DMSO-d6): 61.36
(CH2-5ꢀ); 70.42 (CH-3ꢀ); 73.94 (CH-2ꢀ); 80.71 (d, JC,F = 167,
CH2-F); 85.90 (CH-4ꢀ); 87.87 (CH-1ꢀ); 131.97 (d, JC,F = 2, C-5);
ꢀ
ꢀ
(CH-m-Tol); 129.76 and 129.88 (CH-o-Tol); 132.11 (d, JC,F
=
1, C-5); 143.86 (CH-8); 144.29, 144.63 and 144.76 (C-p-Tol);
151.55 (C-4); 152.69 (CH-2); 154.98 (d, JC,F = 18, C-6); 165.18,
165.39 and 166.17 (CO-Tol). IR (CCl4): m = 3039, 1732, 1612,
1601, 1579, 1498, 1410, 1333, 1266, 1209, 1179,1126, 1113,
1092, 1020, 643 cm−1.
145.74 (CH-8); 151.76 (C-4); 152.08 (CH-2); 153.62 (d, JC,F
17, C-6). 19F NMR (100.6 MHz, DMSO-d6): −216.76 (t, JF,H
=
=
46.6). IR (KBr): m = 3382, 3285, 1603, 1585, 1501, 1417, 1405,
6-(Fluoromethyl)-9-(2-deoxy-3,5-di-O-toluoyl-b-D-erythro-
pentofuranosyl)purine (4d). Yield: 43% with Deoxo-Fluor
(step A), 72% via 6-(iodomethyl)purine 6d (steps B, D, F). White
foam. Exact mass (FAB HR MS) found: 505.1883; calcd for
C27H26FN4O5: 505.1887. FAB MS m/z (%): 505 (MH+, 2); 487
(1); 153 (11); 119 (100). 1H NMR (400 MHz, CDCl3): 2.38 and
1331, 1211, 1119, 1089, 1048, 797, 649 cm−1.
6-(Fluoromethyl)-9-(2-deoxy-b-D-erythro-pentofuranosyl)-
purine (4g). Prepared from 6-(fluoromethyl)purine 2ꢀ-
deoxynucleoside 4d (133 mg, 0.264 mmol) by procedure
described above (see preparation of 4f). Yield: 56 mg (79%) of
white solid (crystalization from MeOH–EtOAc–heptane, mp
ꢀ
ꢀ
2.42 (2 × s, 2 × 3H, CH3-Tol); 2.88 (ddd, 1H, Jgem = 14.2, J2 b,1
=
5.8, J2 b,3 = 2.2, H-2ꢀb); 3.20 (ddd, 1H, Jgem = 14.2, J2 a,1
=
ꢀ
ꢀ
ꢀ
ꢀ
◦
142–143 C). [a]2D0 = −4.3 (c = 4.55, MeOH). Anal. calcd for
8.3, J2 a,3 = 6.4, H-2ꢀa); 4.64–4.70 (m, 2H, H-5ꢀb and H-4ꢀ); 4.80
ꢀ
ꢀ
C11H13FN4O3: C, 49.25; H, 4.88; F, 7.08; N, 20.89; found: C,
49.17; H, 4.81; F, 7.28; N, 20.63. Exact mass (FAB HR MS)
found: 269.1057; calcd for C11H14FN4O3: 269.1050. FAB MS
m/z (%): 269 (MH+, 35); 251 (5); 153 (100); 135 (18). 1H NMR
(dd, 1H, Jgem = 13.3, J5 a,4 = 5.1, H-5ꢀa); 5.85 (dt, 1H, J3 ,2
=
ꢀ
ꢀ
ꢀ ꢀ
6.4, 2.2 J3 ,4 = 2.4, H-3ꢀ); 5.86 (d, 2H, JH,F = 46.6, CH2-F);
ꢀ
ꢀ
6.62 (dd, 1H, J1 2 = 8.3, 5.8, H-1ꢀ); 7.22 and 7.29 (2 × m, 2 ×
2H, H-m-Tol); 7.89 and 7.98 (2 × m, 2 × 2H, H-o-Tol); 8.29 (s,
1H, H-8); 8.93 (s, 1H, H-2). 13C NMR (100.6 MHz, CDCl3):
21.68 and 21.75 (CH3-Tol); 37.85 (CH2-2ꢀ); 63.86 (CH2-5ꢀ);
75.03 (CH-3ꢀ); 80.82 (d, JC,F = 173, CH2-F); 83.25 (CH-4ꢀ);
85.02 (CH-1ꢀ); 126.33 and 126.57 (C-i-Tol); 129.29 and 129.32
(CH-m-Tol); 129.61 and 129.82 (CH-o-Tol); 132.17 (d, JC,F = 3,
C-5); 143.46 (CH-8); 144.25 and 144.61 (C-p-Tol); 151.38 (C-4);
152.44 (CH-2); 154.79 (d, JC,F = 18, C-6); 165.94 and 166.12
(CO-Tol). IR (CCl4): m = 3039, 1727, 1613, 1601, 1588, 1497,
1408, 1332, 1267, 1210, 1178,1100, 1021 cm−1.
ꢀ
ꢀ
ꢀ
ꢀ
(400 MHz, DMSO-d6): 2.37 (ddd, 1H, Jgem = 13.3, J2 b,1 = 6.4,
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
J2 b,3 = 3.7, H-2 b); 2.80 (ddd, 1H, Jgem = 13.3, J2 a,3 = 7.1, J2 a,1
=
5.9, H-2ꢀa); 3.53 (ddd, 1H, Jgem = 11.8, J5 b,OH = 5.5, J5 b,4
=
ꢀ
ꢀ
ꢀ
4.7, H-5ꢀb); 3.63 (dt, 1H, Jgem = 11.8, J5 a,OH = 5.5, J5 a,4 = 5.2,
ꢀ
ꢀ
ꢀ
H-5ꢀa); 3.90 (td, 1H, J4 ,5 = 5.2, 4.7, J4 ,3 = 3.1, H-4ꢀ); 4.46 (dq,
ꢀ
ꢀ
ꢀ ꢀ
1H, J3 ,2 = 7.1, 3.7, J3 ,OH = 4.1, J3 ,4 = 3.1, H-3ꢀ); 4.98 (t, 1H,
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
JOH,5 = 5.5, OH-5ꢀ); 5.37 (d, 1H, JOH,3 = 4.1, OH-3ꢀ); 5.83 (d,
ꢀ
ꢀ
2H, JH,F = 46.7, CH2-F); 6.50 (t, 1H, J1 2 = 6.4, 5.9, H-1ꢀ);
8.86 (s, 1H, H-8); 8.97 (s, 1H, H-2). 13C NMR (100.6 MHz,
DMSO-d6): 39.44 (CH2-2ꢀ); 61.65 (CH2-5ꢀ); 70.73 (CH-3ꢀ); 80.69
(d, JC,F = 167, CH2-F); 83.99 (CH-1ꢀ); 88.21 (CH-4ꢀ); 131.99
(C-5); 145.71 (CH-8); 151.46 (C-4); 151.97 (CH-2); 153.47 (d,
JC,F = 17, C-6). 19F NMR (188.2 MHz, DMSO-d6): −216.69 (t,
JF,H = 46.7). IR (KBr): m = 3371, 3212, 1598, 1500, 1450, 1398,
1342, 1331, 1207, 1102, 1060, 1027, 751, 645 cm−1.
ꢀ
ꢀ
6-(Fluoromethyl)-9H-purine
(4e). 6-(Fluoromethyl)-9-
(tetrahydropyran-2-yl)purine 4b (92 mg, 0.389 mmol) was
dissolved in ethanol (10 ml) and Dowex 50 WX8 (H+ form)
(ca. 20 mg) was added. This suspension was stirred for 1 h
at 75 ◦C. After a complete deprotection of starting material,
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 0 0 1 – 3 0 0 7
3 0 0 5

View Online
ꢀ
ꢀ
ꢀ ꢀ
General procedure for preparation of
6-(methanesulfonyloxymethyl)purines (5)
6.4, 2.3, J3 ,4 = 2.3, H-3ꢀ); 6.60 (dd, 1H, J1 2 = 8.3, 5.9, H-1ꢀ);
7.22 and 7.29 (2 × m, 2 × 2H, H-m-Tol); 7.89 and 7.98 (2 ×
m, 2 × 2H, H-o-Tol); 8.29 (s, 1H, H-8); 8.93 (s, 1H, H-2).
13C NMR (100.6 MHz, CDCl3): 21.69 and 21.75 (CH3-Tol);
37.83 (CH2-2ꢀ); 38.45 (CH3-S); 63.86 (CH2-5ꢀ); 66.50 (CH2-O);
74.98 (CH-3ꢀ); 83.27 (CH-4ꢀ); 85.11 (CH-1ꢀ); 126.30 and 126.56
(C-i-Tol); 129.29 and 129.32 (CH-m-Tol); 129.61 and 129.81
(CH-o-Tol); 132.64 (C-5); 143.72 (CH-8); 144.29 and 144.63
(C-p-Tol); 151.41 (C-4); 152.49 (CH-2); 152.77 (C-6); 165.93
and 166.11 (CO-Tol). IR (CHCl3): m = 1721, 1612, 1602, 1497,
1408, 1358, 1334, 1269, 1178, 1102, 1042, 1021, 966, 840, 644,
526, 508 cm−1.
A solution of 6-(hydroxymethyl)purine 3 (1 mmol) in CH2Cl2
(2 ml) was added to a mixture of methanesulfonic anhy-
dride (209 mg, 1.2 mmol), Et3N (0.2 ml, 1.4 mmol) and
4-(dimethylamino)pyridine (5 mg) in CH2Cl2 (8 ml). After
consumption of starting material (2 h), the reaction mixture
was directly applied on a column of silica gel and product was
eluted with hexanes–ethyl acetate 1 : 1–1 : 3.
9-Benzyl-6-(methanesulfonyloxymethyl)purine (5a). Yield:
93% as white solid. Exact mass (FAB HR MS) found: 319.0859;
calcd for C14H15N4O3S: 319.0865. FAB MS m/z (%): 319 (MH+,
100); 225 (25); 91 (76). 1H NMR (400 MHz, CDCl3): 3.24
(s, 3H, CH3-S); 5.47 (s, 2H, CH2-N); 5.76 (s, 2H, CH2-O);
General procedure for preparation of 6-(iodomethyl)purines (6)
Finkelstein reaction of mesylates (5) with NaI (step D).
A
7.30–7.41 (m, 5H, Ph); 8.10 (s, 1H, H-8); 9.03 (s, 1H, H-2). 13
C
solution of NaI (300 mg, 2 mmol) in acetone (4 ml) was added
to a solution of 6-(methanesulfonyloxymethyl)purine 5 (1 mmol)
in dry acetone (6 ml) under Ar atmosphere. Reaction was
quantitative and completed after 1.5 h. Reaction mixture was
directly applied on a column of silica gel and chromatographed
(hexanes–ethyl acetate 1 : 1–1 : 2).
NMR (100.6 MHz, CDCl3): 38.44 (CH3-S); 47.51 (CH2-N);
66.63 (CH2-O); 127.94, 128.81 and 129.25 (CH-Ph); 131.89
(C-5); 134.70 (C-i-Ph); 145.23 (CH-8); 152.06 (C-4); 152.47
(C-6); 152.65 (CH-2). IR (CHCl3): m = 3033, 1600, 1501, 1406,
1357, 1333, 1177, 1030, 961, 646, 526, 507 cm−1.
6-(Methanesulfonyloxymethyl)-9-(tetrahydropyran-2-yl)purine
(5b). Yield: 96% as white foam. Exact mass (FAB HR MS)
found: 313.0976 calcd for C12H17N4O4S: 313.0971. FAB MS
m/z (%): 313 (MH+,11); 229 (93); 135 (38); 85 (100). 1H
NMR (400 MHz, CDCl3): 1.65–1.88 and 2.02–2.22 (m, 6H,
CH2-THP); 3.24 (s, 3H, CH3-S); 3.80 (td, 1H, J = 11.7 and 2.7,
bCH2-O-THP); 4.20 (ddt, 1H, J = 11.7, 4.2 and 1.8, aCH2-
O-THP); 5.73 and 5.77 (2 × d, 2 × 1H, Jgem = 13.3, CH2-O);
5.83 (dd, 1H, J = 10.3 and 2.5, CH-O-THP); 8.35 (s, 1H,
H-8); 9.00 (s, 1H, H-2). 13C NMR (100.6 MHz, CDCl3): 22.67,
24.79 and 31.81 (CH2-THP); 38.44 (CH3-S); 66.60 (CH2-O);
68.89 (CH2-O-THP); 82.22 (CH-O-THP); 132.01 (C-5); 143.33
(CH-8); 151.22 (C-4); 152.43 (C-6); 152.45 (CH-2). IR (CHCl3):
m = 2951, 2861, 1602, 1496, 1407, 1357, 1334, 1177, 1087, 1045,
959, 526, 508 cm−1.
Direct dehydroxy-iodination (step E). A solution of 6-
(hydroxymethyl)purine 3 (1 mmol) in CH2Cl2 (2 ml) was added
to a solution of Ph3P (314 mg, 1.2 mmol), I2 (305 mg, 1.2 mmol)
i
and Pr2EtN (0.24 ml, 1.4 mmol) in CH2Cl2 (5 ml) under Ar
atmosphere. After consumption of starting material (30 min.),
the reaction mixture was directly applied on a column of silica
gel and product was eluted with hexanes–ethyl acetate 3 : 1–1 : 1.
All 6-(iodomethyl)purines 6a–d were very sensitive for mois-
ture and light. They were used immediately in the next step.
9-Benzyl-6-(iodomethyl)purine (6a). Yield: 88% from 6-
(hydroxymethyl)purine 3a (steps B + D), 68% (step E). White
solid which turned yellow after time (mp 130–131 ◦C). Exact
mass (APCI HR MS) found: 351.0094 calcd for C13H12N4I:
351.0107. FAB MS m/z (%): 351 (MH+, 0.1); 225 (100); 135
(11); 91 (32). 1H NMR (400 MHz, CDCl3): 4.86 (s, 2H, CH2-I);
5.44 (s, 2H, CH2-N); 7.31–7.41 (m, 5H, Ph); 8.10 (s, 1H, H-8);
8.95 (s, 1H, H-2). 13C NMR (100.6 MHz, CDCl3): −2.06 (CH2-
I); 47.56 (CH2-N); 128.04, 128.80 and 129.26 (CH-Ph); 130.91
(C-5); 134.85 (C-i-Ph); 144.38 (CH-8); 151.80 (C-4); 152.83 (CH-
2); 157.82 (C-6). IR (CHCl3): m = 3092, 3069, 3037, 1595, 1500,
1457, 1403, 1332, 1072, 1030, 648, 576 cm−1.
6-(Methanesulfonyloxymethyl)-9-(2,3,5-tri-O-toluoyl-b-D-
ribofuranosyl)purine (5c). Yield: 90% as white foam. Exact
mass (APCI HR MS) found: 715.2083 calcd for C36H34N4O10S:
715.2074. FAB MS m/z (%): 715 (MH+, 5); 487 (10); 228 (4);
1
119 (100). H NMR (500 MHz, CDCl3): 2.38 and 2.43 (2 × s,
9H,CH3-Tol); 3.21 (s, 3H, CH3-S); 4.67 (dd, 1H, Jgem = 12.3,
J5 b,4 = 4.2, H-5ꢀb); 4.83 (td, 1H, J4 ,3 = 4.7, J4 ,5 = 4.2, 3.1,
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
H-4ꢀ); 4.90 (dd, 1H, Jgem = 12.3, J5 a,4 = 3.1, H-5ꢀa); 5.72 (s,
ꢀ
ꢀ
6-(Iodomethyl)-9-(tetrahydropyran-2-yl)purine (6b). Yield:
91% from 6-(hydroxymethyl)purine 3b (steps B + D), 79% (step
2H, CH2-O); 6.20 (dd, 1H, J3 ,2 = 5.8, J3 ,4 = 4.7, H-3ꢀ); 6.38
ꢀ
ꢀ
ꢀ ꢀ
(t, 1H, J2 ,3 = 5.8, J2 ,1 = 5.4, H-2ꢀ); 6.48 (d, 1H, J1 ,2 = 5.4,
H-1ꢀ); 7.16, 7.23 and 7.26 (3 × m, 3 × 2H, H-m-Tol); 7.80,
7.91 and 7.98 (3 × m, 3 × 2H, H-o-Tol); 8.27 (s, 1H, H-8);
8.88 (s, 1H, H-2). 13C NMR (125.8 MHz, CDCl3): 21.71 and
21.75 (CH3-Tol); 38.46 (CH3-S); 63.33 (CH2-5ꢀ); 66.48 (CH2-O);
71.35 (CH-3ꢀ); 73.67 (CH-2ꢀ); 81.12 (CH-4ꢀ); 87.06 (CH-1ꢀ);
125.53, 125.94 and 126.51 (C-i-Tol); 129.25, 129.29 and 129.35
(CH-m-Tol); 129.76, 129.87 and 129.88 (CH-o-Tol); 132.65
(C-5); 144.11 (CH-8); 144.32, 144.66 and 144.80 (C-p-Tol);
151.61 (C-4); 152.74 (CH-2); 152.91 (C-6); 165.18, 165.38 and
166.16 (CO-Tol). IR (CHCl3): m = 1727, 1612, 1601, 1499, 1410,
1359, 1336, 1267, 1179, 1126, 1114, 1093, 1020, 964, 839, 643,
526, 508 cm−1.
1
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
E). Yiellow oil. H NMR (500 MHz, CDCl3): 1.72–1.86 and
2.03–2.20 (m, 6H, CH2-THP); 3.80 (td, 1H, J = 11.8 and 2.6,
bCH2-O-THP); 4.19 (ddt, 1H, J = 11.8, 4.3 and 1.8, aCH2-O-
THP); 4.84 and 4.88 (2 × d, 2 × 1H, Jgem = 9.2, CH2-I); 5.80
(dd, 1H, J = 10.4 and 2.5, CH-O-THP); 8.35 (s, 1H, H-8); 8.91
(s, 1H, H-2). 13C NMR (125.8 MHz, CDCl3): −2.11 (CH2-I);
22.71, 24.81 and 31.80 (CH2-THP); 68.87 (CH2-O-THP); 82.12
(CH-O-THP); 131.03 (C-5); 142.39 (CH-8); 150.90 (C-4); 152.59
(CH-2); 157.78 (C-6). IR (CHCl3): m = 2952, 2862, 1597, 1495,
1403, 1334, 1087, 1046, 913, 876, 645, 589 cm−1.
6-(Iodomethyl)-9-(2,3,5-tri-O-toluoyl-b-D-ribofuranosyl)purine
(6c). Yield: 84% from 6-(hydroxymethyl)purine 3c (steps B +
D). Yellowish foam. FAB MS m/z (%): 747 (MH+, 0.5); 621
(8); 487 (10); 119 (100). 1H NMR (400 MHz, CDCl3): 2.38 and
6-(Methanesulfonyloxymethyl)-9-(2-deoxy-3,5-di-O-toluoyl-
b-D-erythro-pentofuranosyl)purine (5d). Yield: 95% as white
solid. Exact mass (FAB HR MS) found: 581.1717 calcd for
C28H29N4O8S: 581.1706. FAB MS m/z (%): 581 (MH+,6); 353
(2); 229 (26); 135 (48); 119 (100). 1H NMR (400 MHz, CDCl3):
ꢀ
ꢀ
2.42 (2 × s, 9H,CH3-Tol); 4.66 (dd, 1H, Jgem = 12.3, J5 b,4
=
4.1, H-5ꢀb); 4.82 (s, 2H, CH2-I); 4.83 (td, 1H, J4 ,3 = 4.7, J4 ,5
=
ꢀ
ꢀ
ꢀ ꢀ
4.1, 3.1, H-4ꢀ); 4.90 (dd, 1H, Jgem = 12.3, J5 a,4 = 3.1, H-5ꢀa);
ꢀ
ꢀ
6.21 (dd, 1H, J3 ,2 = 5.8, J3 ,4 = 4.7, H-3ꢀ); 6.38 (t, 1H, J2 ,3
=
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
5.8, J2 ,1 = 5.4, H-2ꢀ); 6.47 (d, 1H, J1 ,2 = 5.4, H-1ꢀ); 7.16, 7.22
and 7.26 (3 × m, 3 × 2H, H-m-Tol); 7.82, 7.91 and 7.99 (3 ×
m, 3 × 2H, H-o-Tol); 8.27 (s, 1H, H-8); 8.80 (s, 1H, H-2). 13C
NMR (100.6 MHz, CDCl3): −2.40 (CH2-I); 21.71 and 21.74
(CH3-Tol); 63.37 (CH2-5ꢀ); 71.34 (CH-3ꢀ); 73.68 (CH-2ꢀ); 81.07
ꢀ
ꢀ
ꢀ ꢀ
2.41 and 2.45 (2 × s, 2 × 3H, CH3-Tol); 2.88 (ddd, 1H, Jgem
=
14.2, J2 b,1 = 5.9, J2 b,3 = 2.3, H-2ꢀb); 3.20 (ddd, 1H, Jgem
=
ꢀ
ꢀ
ꢀ
ꢀ
14.2, J2 a,1 = 8.3, J2 a,3 = 6.4, H-2ꢀa); 3.23 (s, 3H, CH3-S);
ꢀ
ꢀ
ꢀ
ꢀ
4.64–4.70 (m, 2H, H-4ꢀ and H-5ꢀb); 4.79 (dd, 1H, Jgem = 13.4,
J5 a,4 = 5.3, H-5ꢀa); 5.72 (s, 2H, CH2-O); 5.84 (dt, 1H, J3 ,2
=
ꢀ
ꢀ
ꢀ ꢀ
3 0 0 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 0 0 1 – 3 0 0 7

View Online
(CH-4ꢀ); 86.96 (CH-1ꢀ); 125.59, 125.98 and 126.55 (C-i-Tol);
129.24, 129.27 and 129.35 (CH-m-Tol); 129.78, 129.87 and
129.89 (CH-o-Tol); 132.62 (C-5); 143.21 (CH-8); 144.26, 144.60
and 144.74 (C-p-Tol); 151.31 (C-4); 152.88 (CH-2); 158.23
(C-6); 165.18, 165.37 and 166.19 (CO-Tol). IR (CHCl3): m =
1727, 1612, 1595, 1497, 1408, 1334, 1268, 1180, 1154, 1126,
1114, 1093, 1020, 839, 643 cm−1.
5 W. B. Parker, S. A. King, P. W. Allan, L. L. Bennett Jr., J. A. Secrist,
III, J. A. Montgomery, K. S. Gilbert, W. R. Waud, A. H. Wells, G. Y.
Gillespie and E. J. Sorscher, Hum. Gene Ther., 1997, 8, 1637–1644.
6 (a) A. A. Henry, A. G. Olsen, S. Matsuda, C. Yu, B. H. Geierstanger
and F. E. Romesberg, J. Am. Chem. Soc., 2004, 126, 6923–6931;
(b) J. S. Lai and E. T. Kool, Chem. Eur. J., 2005, 11, 2966–2971;
(c) A. Zahn, C. Brotschi and C. J. Leumann, Chem. Eur. J., 2005, 11,
2125–2129.
7 S. Cohen, E. Thom and A. Bendich, J. Org. Chem., 1962, 27, 3545–
3549.
8 M. Shimazaki, H. Nakamura, Y. Iitaka and M. Ohno, Chem. Pharm.
Bull., 1983, 31, 3104–3112.
9 (a) W. J. Middleton, J. Org. Chem., 1975, 40, 574–578; (b) L. N.
Markovskii, V. E. Pashinnik and A. V. Kirsanov, Synthesis, 1973,
787–789.
10 (a) S. Takamatsu, S. Katayama, N. Hirose, E. D. Cock, G. Schelkens,
M. Demillequand, J. Brepoels and K. Izawa, Nucleosides, Nucleotides
& Nucleic Acids, 2002, 21, 849–861; (b) B. Bennua-Skalmowski and
H. Vorbru¨ggen, Tetrahedron Lett., 1995, 36, 2611–2614.
11 (a) G. S. Lal, G. P. Pez, R. J. Pesaresi, F. M. Prozonic and H. J. Cheng,
J. Org. Chem., 1999, 64, 7048–7054; (b) B. Dolensky and K. L. Kirk,
Collect. Czech. Chem. Commun., 2002, 67, 1335–1344.
12 (a) F. L. M. Pattison and J. E. Millington, Can. J. Chem., 1956, 34,
757–760; (b) J. E. Herz, J. Fried, P. Grabowich and E. F. Sabo, J. Am.
Chem. Soc., 1956, 78, 4812–4814; (c) M. B. Giudicelli, D. Picq and
B. Veyron, Tetrahedron Lett., 1990, 31, 6527–6530.
13 (a) D. D. Tanner, H. Yabuuchi and E. V. Blackburn, J. Am. Chem.
Soc., 1971, 93, 4802–4808; (b) W. F. Edgell and L. Parts, J. Am. Chem.
Soc., 1955, 77, 4899–4902.
14 (a) S. Levy, E. Livni, D. Elmaleh and W. Curatolo, J. Chem. Soc.,
Chem. Commun., 1982, 972–973; (b) S. W. Landvatter and J. A.
Katzenellenbogen, J. Med. Chem., 1982, 25, 1300–1307.
15 H. Finkelstein, Ber. Dtsch. Chem. Ges., 1910, 43, 1528–1532.
16 G. A. Wiley, R. L. Hershkowitz, B. M. Rein and B. C. Chung, J. Am.
Chem. Soc., 1964, 86, 964–965.
6-(Iodomethyl)-9-(2-deoxy-3,5-di-O-toluoyl-b-D-erythro-
pentofuranosyl)purine (6d). Yield: 89% from 6-(hydroxy-
methyl)purine 3d (steps B + D). Yellowish solid. 1H NMR
(500 MHz, CDCl3): 2.41 and 2.45 (2 × s, 2 × 3H, CH3-Tol);
2.86 (ddd, 1H, Jgem = 14.2, J2 b,1 = 5.8, J2 b,3 = 2.1, H-2ꢀb);
ꢀ
ꢀ
ꢀ
ꢀ
3.19 (ddd, 1H, Jgem = 14.2, J2 a,1 = 8.4, J2 a,3 = 6.4, H-2ꢀa);
ꢀ
ꢀ
ꢀ
ꢀ
4.64–4.70 (m, 3H, H-4ꢀ and H-5ꢀb); 4.78 (dd, 1H, Jgem = 13.4,
J5 a,4 = 5.3, H-5ꢀa); 4.83 (s, 2H, CH2-I); 5.84 (dt, 1H, J3 ,2
=
ꢀ
ꢀ
ꢀ ꢀ
6.4, 2.1, J3 ,4 = 2.2, H-3ꢀ); 6.59 (dd, 1H, J1 2 = 8.4, 5.8, H-1ꢀ);
7.23 and 7.29 (2 × m, 2 × 2H, H-m-Tol); 7.90 and 7.98 (2 ×
m, 2 × 2H, H-o-Tol); 8.30 (s, 1H, H-8); 8.55 (s, 1H, H-2). 13C
NMR (128.5 MHz, CDCl3): −2.27 (CH2-I); 21.71 and 21.76
(CH3-Tol); 37.83 (CH2-2ꢀ); 63.91 (CH2-5ꢀ); 75.03 (CH-3ꢀ); 83.21
(CH-4ꢀ); 85.00 (CH-1ꢀ); 126.33 and 126.60 (C-i-Tol); 129.32
(CH-m-Tol); 129.64 and 129.82 (CH-o-Tol); 131.61 (C-5);
142.81 (CH-8); 144.24 and 144.61 (C-p-Tol); 151.14 (C-4);
152.64 (CH-2); 158.09 (C-6); 165.94 and 166.14 (CO-Tol). IR
(CHCl3): m = 1721, 1612, 1595, 1495, 1456, 1405, 1332, 1269,
1179, 1102, 1021, 841, 645, 584 cm−1.
ꢀ
ꢀ
ꢀ ꢀ
Acknowledgements
This work is a part of the research project Z4 055 0506. It
was supported by the Grant Agency of the Czech Republic
(grant No. 203/03/0035) by the “Centre for New Antivirals and
Antineoplastics” (1M6138896301) and by Sumitomo Chemical,
Inc. (Osaka, Japan).
17 (a) P. Tannhauser, R. J. Pratt and E. V. Jensen, J. Am. Chem. Soc.,
1956, 78, 2658–2659; (b) B. Helferich and R. Gootz, Ber. Dtsch.
Chem. Ges., 1929, 62, 2505–2507.
18 M. Hocek and A. Holy´, Collect. Czech. Chem. Commun., 1995, 60,
1386–1389.
19 G. Zemple´n and A. Kunz, Ber. Dtsch. Chem. Ges., 1923, 56, 1705–
1710.
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3 0 0 7