Synthesis of three regioisomeric (7-methoxychromenonyl)methyl guanosine 5′-phosphates

Article abstract of DOI:10.1080/00397910802379975

Herein we describe the synthesis of three new (7-methoxychromenonyl)methyl 2-N-propionyl-2′,3′-isopropylideneguanosine 5′-phosphate diesters, potentially photolabile nucleotides, via an H-phosphonate strategy. The stability of these compounds toward acidic and basic conditions was evaluated during the nucleoside moiety deprotection. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910802379975

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Synthesis of Three
Regioisomeric (7-
Methoxychromenonyl)methyl
Guanosine 5′-Phosphates
a
a
Elodie Faurel-Paul , Kenta Yoshida , Magali
a
a
a
Sépulcre , Hamid Dhimane & Yves Le Merrer
a
Laboratoire de Chimie et Biochimie
Pharmacologiques et Toxicologiques, UMR-8601
CNRS/Université Paris Descartes , Paris, France
Published online: 08 Jan 2009.
To cite this article: Elodie Faurel-Paul , Kenta Yoshida , Magali Sépulcre ,
Hamid Dhimane & Yves Le Merrer (2009) Synthesis of Three Regioisomeric (7-
Methoxychromenonyl)methyl Guanosine 5′-Phosphates, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 39:3,
459-474, DOI: 10.1080/00397910802379975
To link to this article: http://dx.doi.org/10.1080/00397910802379975
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1
Synthetic Communications , 39: 459–474, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910802379975
Synthesis of Three Regioisomeric
7-Methoxychromenonyl)methyl Guanosine
(
0
5
-Phosphates
Elodie Faurel-Paul, Kenta Yoshida, Magali S e´ pulcre,
Hamid Dhimane, and Yves Le Merrer
Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques,
UMR-8601 CNRS=Universit e´ Paris Descartes, Paris, France
Abstract: Herein we describe the synthesis of three new (7-methoxychromenonyl)
0
0
0
methyl 2-N-propionyl-2 ,3 -isopropylideneguanosine 5 -phosphate diesters, poten-
tially photolabile nucleotides, via an H-phosphonate strategy. The stability of these
compounds toward acidic and basic conditions was evaluated during the nucleoside
moiety deprotection.
0
Keywords: Chromenone, guanosine, H-phosphonate, 5 -monophosphate, nucleo-
tide, phosphate diester
INTRODUCTION
[1]
Since the pioneering work of J. Kaplan et al., who described in 1978 the
synthesis of ATP bearing a photolabile 2-nitrobenzylphosphate group,
the controlled photochemical release of bioactive molecules from their
‘
‘caged’’ (inactive) derivatives has become a powerful tool for investigat-
ing the spatiotemporal dynamics of the released effector molecules. This
technology has since been applied to nucleotides, neurotransmitters,
[
2]
second messengers, and other relevant bioactive compounds. Photoclea-
vable protecting (caging) groups may mask a biological response of a
bioactive compound, both in vivo and in vitro, and since cleavage by light
Received May 28, 2008.
Address correspondence to Hamid Dhimane, Laboratoire de Chimie et Bio-
chimie Pharmacologiques et Toxicologiques (UMR-8601 CNRS), Universite´
Paris Descartes, UFR Biom e´ dicale, 45, rue des Saints-P e` res, 75270 Paris 06,
France. E-mail: hamid.dhimane@parisdescartes.fr
4
59

460
E. Faurel-Paul et al.
0
Figure 1. Targeted (chromenonyl)methyl guanosine 5 -phosphates.
is a very mild deprotection method that is usually orthogonal to other exp-
erimental manipulations, the so-called caging compounds have become
valuable tools in biotechnology and cell biology. Moreover, such com-
pounds are potential photolabile prodrugs in organs that are accessible to
light (UV or 2-photon IR) irradiation. Therefore, many efforts are currently
[
2g]
devoted to the design and synthesis of photolabile bioactive compounds.
Here, we report the synthesis of new caged GMP (guanosine mono-
phosphate) (1) (Figure 1), derived from three regioisomeric hydroxy-
methyl-7-methoxychromenones 4. Unlike the (coumarin-4-yl)methyl
[
3]
group, which is now a popular photolabile moiety since the original
[3b]
work of Furuta et al., no examples of bioactive compounds caged with
its regioisomer (chromen-4-on-3-yl)methyl moiety have been reported
in the literature to date.
RESULTS AND DISCUSSION
Initial attempts at direct alkylation of GMP with 4-(diazomethyl)- or
4
-(bromomethyl)-7-methoxy-2H-chromen-2-one or the corresponding
mesylate in various solvents were unsuccessful. After further failed
experiments with tricoordinated phosphorous compounds, we turned
our attention to the tetracoordinated P(III) phosphorous compounds,
which in recent years have become very useful tools in nucleotide
[
4]
chemistry. Phosphonylation of 2 was first attempted using diphenyl
[5]
phosphite in pyridine or phosphorus trisimidazolium (generated in situ
[6]
from PCl and imidazole in NEt ), but both conditions gave disap-
3
3
pointingly low yields (9% and 18%, respectively). These low yields are
mainly due to workup and purification difficulties, as was pointed out
by Yousefi-Salakdeh and coworkers in the case of adenosine derivati-
[
7b]
ves.
generated H-pyrophosphonate H P O (from 2.5 eq. of PivCl and 5 eq.
Finally, a near-quantitative yield was obtained by using in situ–
4
2
5
[
of phosphorous acid in pyridine) as the phosphonylating agent. Thus,
7]
3
9
was isolated as a triethylammonium H-phosphonate monoester in
7% yield after purification by silica-gel column chromatography.

0
(
Chromenonyl)methyl Guanosine 5 -Phosphates
461
For H-phosphonate diester preparation, benzyl alcohol was used as a
model substrate for coupling with H-phosphonate monoester 3. To this
end, pivaloyl chloride (4 eq) in pyridine was used for activation of
H-phosphonate monoester 3 as a mixed anhydride prior to reaction with
benzyl alcohol, thus leading to the corresponding H-phosphonate
diester in 91% yield after purification by column chromatography.
Following the same procedure, coupling of 3 with hydroxymethylcou-
marine 4a resulted in a quantitative conversion of monoester 3 according
to thin-layer chromatography (TLC) monitoring; however, isolation of
the expected diester 5a proved difficult with only trace amounts of the
H-phosphonate diester obtained always from a mixture containing vari-
able amounts of its hydrolysis compounds (i.e., 2, 3, 4a, and 6a). The
same mixture was obtained from 2 and (7-methoxycoumarin-4-yl)methyl
phosphonate monoester 6a, which was synthesized from alcohol 4a fol-
lowing the procedure employed for the preparation of monoester 3
(
5
Scheme 1). These results clearly indicate the high sensitivity of diester
a to hydrolysis during the final workup and purification on silica gel.
Unlike 5a, its regioisomer 5b could be obtained, albeit in moderate yield
(
4
49%), by coupling of 3 and 3-(hydroxymethyl)-7-methoxy-4H-chromen-
[
8]
-one 4b in the presence of pivaloyl chloride as the activating agent.
These results led us to envision a one-pot sequence whereby the phospho-
diester coupling is followed by an oxidative step to afford the correspond-
ing phosphate diesters, which were expected to be more stable than the
parent H-phosphonates 5. Indeed, when the coupling mixtures leading
to 5 were submitted to oxidative treatment with iodine in pyridine in
the presence of water, the expected phosphate diesters 7 were easily iso-
lated after purification by column chromatography. Diester 7a was
obtained in 91% yield; however, 7b was isolated in only 47% yield, which
is similar to that of its H-phosphonate analog 5b (49%) indicating that
the coupling between 3 and 3-hydroxymethyl-7-methoxychromen-4-one
is the limiting step of this sequence (Scheme 1).
Next, we examined deprotection of the furanose moiety, first with tri-
fluoroacetic acid (TFA) as catalyst in tetrahydrofuran (THF), which led to
diol deprotection and concomitant hydrolysis of the phosphate diester
moiety. Using aqueous HCl in formic acid resulted in a clean hydrolysis
of the acetonide moiety of coumarine derivative 7a, leading to 8a in
8
2% yield. However, under the same conditions, 7b underwent cleavage
of both the acetonide and the phosphate diester moieties, leading to 3-
chloromethyl-7-methoxychromen-4-one via a nucleophilic displacement
of the guanylate by the chloride ion. Phosphate diester 8b was finally iso-
lated in 81% yield when the acetonide cleavage was performed in formic
2
acid without any additive. The final step was the N -propionyl hydrolysis;
compound 1a was quantitatively obtained by treatment of 8a with excess

462
E. Faurel-Paul et al.
0
Scheme 1. Synthesis of (chromenonyl)methyl guanosine 5 -phosphates. Reagents
ꢀ
and conditions: (a) (i) (EtCO) O, DMAP, Py, 70 C; (ii) 2 M NaOH 8 min, then
2
aq
Dowex 50 W ꢁ 8 (pyridinium form); (b) (i) H PO (5 equiv.), PivCl (2.5 equiv.),
3
3
0
Py; (ii) Et
(
3
N, H
i) excess I =Py=H
), Na S O (10% aq) (overall yields: 7a: 91%, 7b: 47%, 7c: 87%); (e) HCO H
2
O (97%); (c) 4 (or 2 or 2 ) (1 equiv.), PivCl (4 equiv.), Py; (d)
þ
ꢂ
2 3
O (w=v=v: 2=100=2); (ii) Et NH , HCO3 buffer (2 M, pH
2
8
2
2
3
2
(
yields 8a: 82%, 8b: 82%, 8b: 81%; 8c: 68%; 1c: 83%; (f) (i) 1 M NaOHaq (7.8
þ
eq.); (ii) Amberlite IR120 H ; (iii) H
decomposition).
2 3
O, Et N (1a: quantitative; 1b and 1c:
of aqueous sodium hydroxide (1 M). Unfortunately, the chromenone ana-
log 8b was totally hydrolyzed under these basic conditions and suffered a
similar fate in the presence of aqueous ammonia.
The results of both deprotection steps demonstrate the more electro-
philic character of chromen-4-one derivatives as compared to chromen-2-
one derivatives. The former may undergo loss of the guanylate either by

0
(
Chromenonyl)methyl Guanosine 5 -Phosphates
463
SN2 reaction or in two steps: 1,4-addition onto the enone system of 7b or
b and subsequent E1CB elimination of guanylate derivative followed by
8
the rearrangement of chromen-4-one fragment, leading to alcohol 4b in
the presence of water or to its chloride in the presence of hydrogen chlor-
ide. Therefore, we thought that the phosphate 9c, derived from the regioi-
someric alcohol 4c, would be a priori less sensitive to basic hydrolysis
because the corresponding 1,4-adducts will not be prone to b-elimination
of guanylate via E1CB mechanism. Coupling of H-phosphonate 3 with
[
9]
alcohol 4c in the presence of pivaloyl chloride led to the H-phosphonate
diester 5c in 49% isolated yield (Scheme 1). However, when this coupling
reaction was followed by an oxidative treatment with iodine in pyridine,
prior to workup, the expected phosphate diester 7c was obtained in 87%
yield after column chromatography. Treatment of the latter with pure
2
formic acid led to the free diol 8c in 68% yield. All attempts at N -amino
group deprotection under basic conditions resulted in a decomposition of
8
ined the same sequence starting from 2 ,3 -O-isopropylideneguanosine
c via the phosphate diester hydrolysis. To avoid this problem, we exam-
0
0
0
[5b]
2
with a free 2-amino group. H-Phosphonate monoester 6c, easily
obtained from alcohol 4c, was efficiently transformed in the oxidative
0
coupling sequence with guanosine acetonide 2 to afford phosphate diester
0
0
7
c in 88% isolated yield (Scheme 1). Final treatment of 7 c with pure
formic acid led to the desired diester 1c in 83% yield (Scheme 1). Subsequ-
ently, we examined the same strategy to reach the regioisomer 1b. Unfortu-
nately, under the same conditions, oxidative coupling of H-phosphonate
0
monoester 6b with 2 led to a complex mixture of products. This result once
more may be attributed to the high electrophilic character of the mixed
anhydride, which is generated in situ from 6b and pivaloyl chloride.
This intermediate may undergo both nucleophilic attack at the phos-
phorous center and 1,4-addition onto the enone system and subsequent
b-elimination of the phosphate moiety. We observed similar c-substitution
when alcohol 4b was involved in a Mitsunobu reaction with perpropiony-
lated guanosine. The latter behaved as nucleophile whose O-6 atom was
linked to the C-2 position of 7-methoxy-3-methylchromen-4-one.
CONCLUSION
0
In summary, we synthesized three new guanosine 5 -phosphate diesters 7
0
0
via an oxidative coupling of 2-N-propionyl-2 ,3 -O-isopropylideneguano-
0
sine 5 -H-phosphonate 3 and three regioisomeric hydroxymethylchrome-
0
0
nones 4. Formic acid–catalyzed hydrolysis of the 2 ,3 -O-isopropylidene
moiety was easily achieved in all cases; however, unlike phosphate 8a, iso-
mers 8b,c were unstable under the various basic conditions required for

464
E. Faurel-Paul et al.
the 2-N-propionyl group hydrolysis. Nevertheless, fully deprotected
phosphate 1c could be obtained in good yield by oxidative coupling of
0
0
0
2
acid-catalyzed hydrolysis of the acetonide moiety. This strategy failed
,3 -O-isopropylideneguanosine 2 and H-phosphonates 6c followed by
0
in obtaining regioisomer 1b starting from 6b and 2 . These results clearly
show that phosphate diesters derived from hydroxymethylchromen-2-one
(7a and 8a) are less sensitive to base-catalyzed hydrolysis than those
derived from hydroxymethylchromen-4-one (7b,c and 8b,c).
EXPERIMENTAL
General Procedures
Unless otherwise specified, materials were purchased from commercial
suppliers and used without further purification. THF was distilled from
sodium=benzophenone ketyl radical, and CH Cl and pyridine were dis-
2
2
tilled from calcium hydride, immediately prior to use. All nonaqueous
reactions were performed in dry glassware under argon and were moni-
tored by TLC with Merck 60 F254 precoated silica (0.2 mm) on glass. Flash
chromatography was performed with Merck Kieselgel 60 (0.2–0.5 mm);
the solvent systems are given as v=v. Analytical data were obtained by
using chromatographically homogeneous samples (TLC). IR spectra were
recorded on a Perkin-Elmer Spectrum One FT IR (Fourier transform
infrared). Optical rotations were measured with a Perkin-Elmer 341 polar-
ꢀ
imeter equipped with a sodium (589 nm) lamp at 20 C. Mass spectra and
electrospray ionization (ESI) were recorded on a LCQ Advantage Fenni-
gan apparatus. Nuclear magnetic spectra were recorded on Bruker ARX
1
50 (250 MHz for H, 63 MHz for C, and 101.25 MHz for P) spec-
13
31
2
trometer. Samples were prepared in CD OD or in CDCl (sometimes with
3
3
addition of one drop of deuterated methanol) at 300 K. Chemical shifts (d)
1
were expressed in parts per million relative to TMS at d ¼ 0 for H, and to
1
3
CDCl at d ¼ 77.16 for C, and coupling constants (J) were expressed in
3
3
1
hertz. For P, chemical shifts were referenced to an external standard of
5% orthophosphoric acid set at 0 ppm. For unambiguous assignment of
8
NMR signals in the case of phosphate diesters (7, 8, and 1 ), we employed
letters (C and G) to distinguish between the chromenone and the guano-
sine nucleus signals.
0 0
-N-Propionyl-2 ,3 -O-isopropylideneguanosine (2)
2
To a suspension of guanosine (4.56 g, 16 mmol) in acetone (330 mL) under
an argon atmosphere, 6.11 g (32 mmol, 2 eq.) of PTSA monohydrate and

0
(
Chromenonyl)methyl Guanosine 5 -Phosphates
465
2
4 mL (0.1196 mol, 12.25 eq.) of 2,2-dimethoxypropane were added.
After 2 h stirring at room temperature, 6.34 mL (52 mmol, 3 eq.) of
triethylamine were added, and the resulting solution was concentrated.
The resulting dry residue was dissolved in dry pyridine (95 mL) before
addition of 2.15 g (17.65 mmol, 1.1 eq.) of 4-dimethylaminopyridine
and 34 mL (0.24 mol, 15 eq.) of propionic anhydride. After 5 h of heating
ꢀ
at 70 C, the reaction mixture was concentrated under vacuum, then neu-
tralized with saturated aqueous solution of sodium carbonate until the
end of carbon dioxide evolvement. The resulting aqueous mixture was
extracted with methylene chloride (3 ꢁ 30 mL), and the combined organic
phases were washed with saturated aqueous solution of sodium bicarbon-
ate (20 mL), then dried on MgSO , filtrated, and concentrated under vac-
4
uum. To the residue dissolved in ethanol (50 mL) and pyridine (50 mL),
1
16 mL (0.116 mol) of 1 M sodium hydroxide solution in a 1=1 EtOH=
H O system were added. The resulting mixture was stirred for 8 min at
2
room temperature, then the reaction quenched with approximately
2
00 mL of Dowex 50 W ꢁ 8 (pyridinium form). After filtration and wash-
ing of the Dowex with methylene chloride and then ethanol, the filtrate
was concentrated under vacuum, and the resulting dry residue was sub-
mitted to purification by column chromatography eluting with
CH Cl =MeOH (95=5), leading to 4.24 g (70%) of 2 as a yellow foam.
2
2
2
D
0
1
R ¼ 0.33 (CH Cl =MeOH: 95=5); ½aꢃ ꢂ 57 (c 1.0, CH Cl ); H NMR
f
2
2
2
2
(
8
CDCl ): d (ppm) 12.3 (s, 1H, NH), 10.5 (s, 1H, NH), 8.13 (s, 1H, H-
3
0
), 6.04 (d, 1H, J
0
0
0
¼ 3.0 Hz, H-1 ), 5.33 (dd, 1H, J
0 0
¼ 3.0 Hz,
1
,2
1 ,2
0
J2
0
0
¼ 6.0 Hz, H-2 ), 5.13 (dd, 1H, J
0
0
¼ 6.0 Hz, J
0 0
3 ,4
¼ 3 Hz, H-3 ),
,3
2 ,3
0
4
.48 (bs, 1H, J
0
0
0
¼ 3.4 Hz, H-4 ), 4.01 (dd, 1H, J
0
0
¼ 12.0 Hz,
3
,4
5 a,5 b
J4
H-5 a), 3.90 (dd, 1H, J
0
¼ 4.5 Hz,
,5 a
0
0
0
0
¼ 12.0 Hz, J
0 0
4 ,5 b
¼ 4.5 Hz, H-5 ;b), 2.74 (q,
5
a,5 b
2
1
1
H, J ¼ 8.3 Hz, CH CH CO), 1.67 (s, 3H, CH ), 1.45 (s, 3H, CH ),
3
2
3
3
1
3
.32 (t, 3H, J ¼ 8.3 Hz, CH CH CO); C NMR (CDCl ): d (ppm)
3 2 3
76.9 (EtCO), 155.8, 148.2 (Cq), 139.0 (C8), 121.2 (Cq), 114.2
0 0 0 0 0
C(CH ) ], 91.3 (C ), 86.9 (C4 ), 84.1 (C2 ), 81.2 (C3 ), 62.4 (C5 ), 30.3
3 2 1
[
(
CH CH CO), 27.0, 25.0 (CH ), 8.7 (CH CH CO).
3 2 3 3 2
0
0
Triethylammonium 2-N-Propionyl-2 ,3 -O-isopropylideneguanosine
0
5
-H-Phosphonate (3)
Guanosine derivative 2 (1.9 g, 5 mmol) was dried by repeated coevapora-
tion with freshly distilled pyridine (3 ꢁ 5 mL), then dissolved in dry pyri-
dine (15 mL). To this solution, a solution of phosphorous acid (2.1 g,
2
1
5 mmol, 5 eq.) and pivaloyl chloride (1.53 mL, 12.5 mmol, 2.5 eq.) in
5 mL of dry pyridine was added at room temperature. After overnight

466
E. Faurel-Paul et al.
stirring at rt, a mixture of NEt (14 mL) and water (6.5 mL) was added to
3
the obtained slurry, and stirring continued for 10 min. The mixture was
concentrated under vacuum, and the residue was taken in THF before
filtration. Concentration of the resulting filtrate and subsequent purifi-
cation on column silica gel using CH Cl =MeOH=Et N (90=10=
2
2
3
0
9
1
.1) as eluent afforded pure triethylammonium phosphonate 3 (2.65 g,
2
0
7%) as a white foam. R ¼ 0.13 (CH Cl =MeOH; 80=20); ½aꢃ ꢂ 70 (c
f
2
2
D
1
.0, CH Cl ); H NMR (CDCl ): d (ppm) 12.8 (s, 1H, NH), 12.3 (s, 1H,
2
2
3
1
NH), 7.62 (s, 1H, H-8), 6.99 (d, 1H, J ¼ 650 Hz, H-P), 5.90 (bs,
H,P
0
0
1
1
H, H-1 ), 5.61 (dd, 1H, J
0
0
0
¼ 6.4 Hz, J
0 0
3 ,4
¼ 3.0 Hz, H-3 ), 5.08 (bs,
2
,3
0
H, J
0
0
0
¼ 6.4 Hz, H-2 ), 4.80–4.67 (m, 1H, H-5 a), 4.39–4.34 (m, 1H,
2
,3
0
þ
H-4 ), 3.80–3.72 (m, 1H, H-5b ), 3.06 [q, 6H, J ¼ 8.5 Hz (CH CH ) NH ],
3
2 3
2
.56 (q, 2H, J ¼ 8.4 Hz, CH CH CO), 1.53 (s, 3H, CH ), 1.32 [m, 12H,
þ
3 3 2 3 3 2
3
2
3
13
CH , (CH CH ) NH ], 1.16 (t, 3H, J ¼ 8.0 Hz, CH CH CO);
C
NMR (CDCl ): d (ppm) 178.1 (CH CH CO), 156.2, 148.0 (Cq), 139.0
3
3
2
0 0 0
C8), 122.4 (Cq), 113.9 [C(CH ) ], 92.1 (C1 ), 87.8 (C4 ), 85.7 (C2 ),
3 2
(
0 0
þ
2.8 (C3 ), 62.8 (C5 ), 46.1 [(CH CH ) NH ], 30.3 (CH CH CO), 27.6,
3 2 3 3 2
8
2
þ
31
6.0 (CH ), 9.03 [CH CH CO, (CH CH ) NH ]; P NMR(CDCl ): d
3
3
2
3
2 3
3
(ppm) þ 3.5.
Triethylammonium (7-Methoxycoumarin-4-yl)methyl H-Phosphonate (6a)
This was prepared from alcohol 4a (0.2 g, 0.96mmol), phosphorous acid
(0.4 g, 4.8 mmol, 5 eq.), and pivaloyl chloride (0.3 mL, 2.4 mmol, 2.5 eq.),
according to the procedure described for the preparation of compound 3.
Pure triethylammonium H-monophosphonate 6a was isolated by column
chromatography as an amorphous beige solid (273 mg, 76%). R ¼ 0.40
f
1
(
CH Cl =MeOH; 80=20); H NMR (CDCl ) d (ppm) 7.28 (d, 1H,
2
2
3
1
J5,6 ¼ 8.6Hz, H-5), 6.82 (d, 1H, J ¼ 624 Hz, H-P), 6.66–6.57 (m, 2H, H-
H,P
3
, H-8), 6.30 (bs, 1H, H-3), 4.92 (d, 2H, J
6
3
9
1
1
8
¼ 7.7 Hz, CH OP), 3.67 (s,
H=P
2
þ
H, CH O), 2.93 [q, 6H, J ¼ 7.3Hz, (CH CH ) NH ], 1.17 [t,
3
3
2 3
þ
13
H, J ¼ 7.3 Hz, (CH CH ) NH ]; C NMR (CDCl ): d (ppm) 162.6 (C7),
3
2 3
3
61.6 (C2), 155.2 (C9), 152.1 (C4), 124.6 (C5), 112.4 (C6), 110.7 (C10),
þ
08.1 (C3), 101.0 (C8), 61.3 (CH O), 55.7 (CH O), 45.8 [(CH CH ) NH ],
2
3
3
2 3
þ
31
.41 [(CH CH ) NH ]; P NMR(CDCl ): d (ppm) þ 3.5.
3
2 3
3
Triethylammonium (7-Methoxy-4-oxo-4H-chromen-3-yl)methyl
H-Phosphonate (6b)
Starting from 2.47 g (12 mmol) of alcohol 4a, and according the previous
procedure, triethylammonium phosphonate 6b was obtained as a foamy
liquid (4.01 g, 90%). R ¼ 0.15 (MeOH=CH Cl ; 20=80); IR (neat) 3349,
f
2
2

0
(
Chromenonyl)methyl Guanosine 5 -Phosphates
467
ꢂ1; 1
2
8
978, 2938, 1648 cm
H NMR (CD OD): d (ppm) 8.25 (s, 1H, H-8),
3
.06 (d, J ¼ 10 Hz, 1H, 5-H), 7.08 (d, J ¼ 10 Hz, 1H, 6-H), 6.89 (d,
J ¼ 623 Hz, 1H, H-P), 6.22 (s, 1H, 2-H), 4.83 (s, 2H, ꢂCH O), 3.96 (s,
2
þ
1
H, ꢂOCH ), 3.21 (q, J ¼ 7.5 Hz, 6H, [(CH CH ) NH ], 1.34 (t,
3
3
2 3
þ
13
J ¼ 7.5 Hz, 9H, [(CH CH ) NH ); C NMR (63 MHz, CD OD): d
3
2 3
3
(
(
[
ppm) 178.4 (C4), 166.8 (C7), 160.6 (C9), 156.9 (C2), 128.3 (C5), 123.2
Cq), 119.2 (Cq), 117.2 (C6), 102.2 (C8), 62.2 (CH ) 59.8 (CH O), 48.4
2
3
þ
þ
31
(CH CH ) NH ], 9.7 [(CH CH ) NH ]; P NMR (CD OD) d (ppm)
3 2 3 3 2 3 3
þ 5.4.
Triethylammonium (7-Methoxy-4-oxo-4H-chromen-2-yl)methyl
H-Phosphonate (6c)
Reaction of 1.35 g (6.5 mmol) of alcohol 4c, 2.67 g (32.5 mmol) of phos-
phorous acid, and 2 mL (16.3 mmol) of pivaloyl chloride, following
the same procedure as for 6a, led to 1.79 g (71%) of 6c. R ¼ 0.32
f
ꢂ1;
1
(
MeOH=CH Cl ; 20=80); IR (neat) 3414, 2993, 2948, 1650 cm
2
H
2
NMR (CD OD): d (ppm) 7.74 (d, J ¼ 10 Hz, 1H, 5-H), 6.79 (d, J ¼ 10 Hz,
3
1
3
H, 6-H), 6.77 (s, 1H, 8-H), 6.76 (d, J ¼ 630 Hz, 1H, H-P), 6.22 (s, 1H,
-H), 4.67 (d, J ¼ 7.5 Hz, 2H, ꢂCH O), 3.73 (s, 3H, ꢂOCH ), 3.03
2
3
þ
[
q, J ¼ 7.5 Hz, 6H, (CH CH ) NH ], 1.15 [t, J ¼ 7.5 Hz, 9H,
3
2 3
þ
13
CH CH ) NH ]; C NMR (CD OD): d (ppm) 179.9 (C4), 167.8 (Cq),
3 2 3 3
(
1
1
66.6 (Cq), 159.9 (Cq), 128.0 (C5), 118.7 (C10), 116.5 (C6), 109.9 (C3),
þ
01.9 (C8), 63.2 (CH O) 57.2 (MeO) 48.1 [(CH CH ) NH ], 9.7
2
3
2 3
þ
31
[
(CH CH ) NH ]; P NMR (101.25 MHz, CD OD) þ 4.8.
3
2 3
3
General Procedure for the Preparation of Triethylammonium Phosphates
0
7
and 7 (1-mmol Scale)
0
Equimolar mixture of alcohol 4 (or 2 ) and triethylammonium phospho-
nate 3 (or 6c) was coevaporated with freshly distilled pyridine (3 ꢁ 5 mL)
and dissolved in dry pyridine (10 mL) under an argon atmosphere. To
ꢀ
this solution, cooled at 0 C, pivaloyl chloride (4 eq) was added dropwise.
ꢀ
The resulting mixture was stirred for 35 min at 0 C and 2 h at rt, before
oxidative treatment with 20 mL of the mixture I =pyridine=H O (w=v=v:
2
2
2
=100=2). After 15 min stirring at rt, the mixture was diluted in CH Cl
2 2
and then concentrated under vacuum. The residue was taken in 20 mL
of methylene chloride and washed with a mixture of 20 mL of aqueous
2
M triethylammonium bicarbonate buffer (TEAB) and 20 mL of 10%
aqueous Na S O solution. The organic layer was dried over MgSO
4
2
2
3
and evaporated to dryness after filtration. The residue was submitted to

468
E. Faurel-Paul et al.
purification by silica-gel column chromatography using CH Cl =MeOH=
2
2
Et N (90=10=0.2 then 85=15=0.2) as eluent.
3
Triethylammonium (7-Methoxy-2-oxo-2H-chromen-4-yl)methyl
0 0 0
2
-N-Propionyl-2 ,3 -O-isopropylideneguanosine 5 -Phosphate (7a)
This was isolated as a white foam (653 mg, 91%), starting from 500 mg
0.92 mmol) of salt 3 : R ¼ 0.56 (CH Cl =MeOH; 80=20); MS (ESIþ ,
(
f
2
2
þ
þ
20
D
m=z): 749 [M þ H] , (ESIꢂ , m=z): 646 [M–Et NH ]; ½aꢃ ꢂ 23 (c 1,
3
1
CH Cl ); H NMR (CDCl ): d (ppm) 12.6 (s, 1H, NH), 7.65 (s, 1H,
2
2
3
8
G-H), 7.31 (d, 1H, J5,6 ¼ 8.6 Hz, 5C-H), 6.77–6.71 (m, 2H, 6C-H, 8C-
0
0
H), 6.38 (s, 1H, 3C-H), 5.92 (bs, 1H, 1 G-H), 5.66–5.62 (m, 1H, 3 G-H),
0 0
.09–5.02 (m, 3H, CH O , 2 G-H), 4.77–4.75 (m, 1H, 5 G-H), 4.38–4.33
2 C
5
0
0
(
(
m, 1H, 4 G-H), 3.84–3.82 (m, 4H, CH O, 5 G-H), 2.87 [q, 6H, J ¼ 7.2 Hz,
3
þ
CH CH ) NH ], 2.57 (q, 2H, J ¼ 7.4 Hz, CH CH CO), 1.51 (s, 3H,
3
2 3
3
2
þ
CH ), 1.28 (s, 3H, CH ), 1.20 [t, 9H, J ¼ 7.5 Hz, (CH CH ) NH ], 1.11
3
3
3
2 3
1
3
(
(
1
t, 3H, J ¼ 7.5 Hz, CH CH CO); C NMR (CDCl ): d (ppm) 177.6
3
2
3
EtCO), 162.7 (Cq), 161.2 (Cq), 155.8 (Cq), 151.9 (Cq), 148.6 (Cq),
47.5 (Cq), 138.5 (C8G), 124.4 (C5C), 122.1 (Cq), 113.6 [C(CH ) ],
3 2
0
0
1
12.1 (C6C), 110.7 (C10C), 109.2 (C3C), 101.2 (C8C), 91.6 (C1 G), 87.2
0
0
0
0
2
C4 G), 85.3 (C2 G), 82.1 (C3 G), 64.0 (d, J
(
¼ 4.0 Hz, C5 G), 63.0
C5 -P
2
d, J
þ
(
¼ 4.0 Hz, CH OC), 55.7 (CH OC), 46.0 [(CH CH ) NH ],
CH -P
2
2
3
3
2 3
þ
2
9.8 (CH CH CO), 27.3, 25.7 (CH ), 9.8 [(CH CH ) NH ], 8.8
2 3
3
2
3
3
3
1
(CH CH CO); P NMR (CDCl ): d (ppm) ꢂ0.6.
3
2
3
Triethylammonium (7-Methoxy-4-oxo-4H-chromen-3-yl)methyl 2-N-
0
0
0
Propionyl-2 ,3 -O-isopropylideneguanosine 5 -Phosphate (7b)
This was isolated as a white foam (320 mg, 47%), starting from 500 mg
(
0.92 mmol) of salt 3: R ¼ 0.36 (CH Cl =MeOH: 80=20); MS (ESIþ ,
þ þ
3
f
2
2
20
D
m=z): 749 [M þ H] , (ESIꢂ , m=z): 646 [M–Et NH ]; ½aꢃ ꢂ 33 (c 0.5,
1
CH Cl ); H NMR (CDCl ): d (ppm) 12.7 (s, 1H, NH); 12.2 (s, 1H,
2
2
3
NH); 8.02 (d, 1H, J5,6 ¼ 8.9 Hz, 5C-H),7.91 (s, 1H, 2C-H), 7.65 (s, 1H,
8
G-H), 6.91 (bs, 1H, J ¼ 8.9 Hz, 6C-H), 6.79 (bs, 1H, 8C-H), 5.93
6
,5
0
0
(
J2
bs, 1H, 1 G-H), 5.72 (d, 1H, J
0
0
0
,4
¼ 3.3 Hz, 3 G-H), 5.07 (d, 1H,
3
0
0
0
¼ 6.2 Hz, 2 G-H), 4.90–4.75 (m, 3H, CH O , 5 G-H), 4.37–4.32
,3
2
C
0
0
(m, 1H, 4 G-H), 3.86–3.77 (m, 4H, CH O , 5 G-H), 3.02 [q, 6H,
3
C
þ
J ¼ 7.3 Hz, (CH CH ) NH ], 2.67–2.53 (m, 2H, CH CH CO), 1.51 (s,
3
2 3
3
2
þ
H, CH ), 1.32–1.25 [m, 12H, CH , (CH CH ) NH ], 1.13 (t, 3H,
3 3 3 2 3
3
1
3
J ¼ 7.5 Hz, CH CH CO); C NMR (CDCl ): d (ppm) 177.8 (C4C),
3
2
3
1
1
75.9 (CH CH CO), 164.1 (Cq), 158.2 (Cq), 155.8 (Cq), 153.1 (C2C),
3 2
48.6 (Cq), 147.5 (Cq), 138.5 (C8G), 126.8 (C5C), 122.9 (Cq), 121.4

0
(
Chromenonyl)methyl Guanosine 5 -Phosphates
469
0
Cq), 121.2 (Cq), 114.7 [C(CH ) ], 113.4 (C6C), 100.2 (C8C), 91.7 (C1 G),
3 2
(
0
0
0
0
8
7.7 (C4 G), 85.5 (C2 G), 82.3 (C3 G), 63.9 (C5 G), 59.7 (CH OC), 55.8
2
þ
(CH OC), 45.8 [(CH CH ) NH ], 29.8 (CH CH CO), 27.2 (CH ),
3
3
2 3
3
2
31
3
þ
2
5.6 (CH ), 8.9 [CH CH CO, (CH CH ) NH ]; P NMR (CDCl3):
3
3
2
3
2 3
d (ppm) ꢂ0.3.
Triethylammonium (7-Methoxy-4-oxo-4H-chromen-2-yl)methyl 2-N-
0
0
0
Propionyl-2 ,3 -O-isopropylideneguanosine 5 -Phosphate (7c)
This was isolated as a pale-yellow syrup foam (1.042 g, 87%), starting
from 870 mg (1.6 mmol) of salt 3: R ¼ 0.4 (MeOH=CH Cl ; 20=80);
f
2
2
þ
20
D
1
MS (ESIþ , m=z) ¼ 749 [M þ H] ; ½aꢃ ꢂ 14.2 (c 1, MeOH); H NMR
(
CDCl ): d (ppm) 12.38 (s, 1H, NH), 12.24 (s, 1H, NH), 8.06 (d,
3
J ¼ 10 Hz, 1H, 5C-H), 7.63 (s, 1H, 8G-H), 6.96 (d, J ¼ 10 Hz, 1H,
0
6
5
C-H), 6.76 (s, 1H, 8C-H), 6.38 (s, 1H, 3C-H), 5.91 (s, 1H, 1 G-H),
0
0
.61 (bs, 1H, 3 G-H), 5.13 (bd, 1H,J ¼ 5 Hz, 2 G-H), 4.78–4.74 (m, 3H,
0
0
ꢂCH OC and 5 G-H), 4.39–4.35 (m, 1H, 4 G-H), 3.89 (s, 4H, OCH
2
3
0
þ
and 5 G-H), 3.07 [q, J ¼ 7.5 Hz, 6H, (CH CH ) NH ], 2.59 (q,
3
2 3
J ¼ 6.3 Hz, 2H, CH CH CO), 1.55 (s, 3H, CH ), 1.38–1.26 [m, 12 H,
3
2
3
þ
13
CH , (CH CH ) NH ], 1.15 (q, J ¼ 6.3 Hz, 3H, CH CH CO);
C
3
3
2 3
3
2
2
NMR (CDCl ): d (ppm) 177.40 (C4C), 177.38 (N ꢂCO), 164.9 (Cq),
3
1
1
(
(
64.0 (Cq), 157.6 (Cq), 155.7 (Cq), 148.2 (Cq), 147.7 (Cq), 138.8 (C8G)
26.6 (C5C), 123.7 (Cq), 121.2 (Cq), 117.2 (Cq), 114.4 (CMe ), 113.5
2
0 0 0
C6C), 108.4 (C8C) 100.0 (C1 G), 88.2 (C4 G), 84.9 (C2 G), 81.7
þ
0
0
C3 G), 64.4 (C5 G), 63.1 (CH OC), 55.7 (MeO), 45.8 [(CH CH ) NH ],
2
3
2 3
]
(
, 29.8 (CH CH CO), 27.0 (CH ), 25.3 (CH ), 8.6 [CH CH CO and
3 2 3 3 3 2
þ
31
CH CH ) NH ]; P NMR (CDCl ): d (ppm) ꢂ0.48.
3
2 3
3
0
0
Triethylammonium (7-Methoxy-4-oxo-4H-chromen-2-yl)methyl 2 ,3 -
0
0
Isopropylidene-O-guanosine 5 -Phosphate (7 c)
This was isolated as a pale-yellow syrup foam (0.605 g, 88%), starting
from 370 mg (1 mmol) of salt 6c: R ¼ 0.17 (MeOH=CH Cl : 20=80);
f
2
2
þ
MS (ESIþ , m=z) ¼ 693 [M þ H] ; IR (neat) 3310 (OH), 3097, 2986
ꢂ1
Ar), 1690, 1650 (C=O) cm
; H NMR (CDCl ): d (ppm) 8.03 (d,
3
1
(
J ¼ 7.5 Hz, 1H, 5C-H), 7.51 (s, 1H, 8G-H), 7.13 (d, J ¼ 10 Hz, 1H, 6C-
0
H), 6.81 (s, 1H, 8C-H), 6.40 (s, 1H, 3C-H), 5.86 (s, 1H, 1 G-H), 5.34
0
0
(bs, 1H, 3 G-H), 5.25 (bd, 1H, J ¼ 5.5 Hz, 2 G-H), 4.91–4.78 (m, 3H,
CH O and 5 G-H), 4.65–4.23 (m, 1H, 4 G-H), 3.90–3.60 (m, 4H,
0
0
0
2 C
þ
ꢂOCH and 5 G-H), 3.11 [q, J ¼ 7.5 Hz, 6H, (CH CH ) NH ], 1.28
3
3
2 3
þ
13
t, J ¼ 7.5 Hz, 9H, (CH CH ) NH ]; C NMR (CDCl ): d (ppm)
[
1
3
2 3
3
77.6, 165.0, 165.0, 164.1, 158.5, 158.1, 154.5, 150.6, 136.2, 130.8,

470
E. Faurel-Paul et al.
1
3
28.8, 126.9, 117.8, 114.3, 113.6, 109.1, 100.3, 69.5, 63.5, 55.8, 53.8, 45.7,
3
1
1.7, 29.3, 27.1, 25.4, 8.6; P NMR (CDCl ): d (ppm) ꢂ0.41.
3
Triethylammonium (7-Methoxy-2-oxo-2H-chromen-4-yl)methyl 2-N-
0
Propionyl-guanosine 5 -Phosphate (8a)
A solution of compound 7a (210 mg, 0.28 mmol) in formic acid
(
1.3 mL) was stirred for 26 h at room temperature. Concentration
under vacuum and repeated coevaporation with absolute ethanol and
purification by silica-gel column chromatography
CH Cl =MeOH=Et N: 85=15=0.2 to 80=20=0.2) led to 162 mg (82%)
(
2
2
3
of compound 8a. R ¼ 0.30 (CH Cl =MeOH; 80=20); MS (ESIþ ,
f
2
2
þ
þ
1
m=z): 709 [M þ H] , (ESIꢂ , m=z): 606 [M–Et NH ]; H NMR
3
(
CDCl ): d (ppm) 7.91 (s, 1H, 8G-H), 7.16 (d, 1H, J ¼ 8.7 Hz, 5C-
3
5,6
H), 6.74 (d, 1H, J ¼ 2.1 Hz, 8C-H), 6.67 (dd, 1H, J ¼ 8.8 Hz,
0
J ¼ 2.1 Hz, 6C-H), 6.42 (bs, 1H, 3C-H), 5.83 (d, 1H,J ¼ 4.6 Hz, 1 G-
0
0
H), 5.15–4.92 (m, 3H, 2 G-H, CH OC), 4.59–4.57 (m, 1H, 3 G-H),
2
0
0
4
.26–4.24 (m, 3H, 4 G-H, 5 G-H), 3.83 (s, 3H, CH OC), 2.89 [q, 6H,
3
þ
J ¼ 7.3 Hz, (CH CH ) NH ], 2.51 (q, 2H, J ¼ 7.2 Hz, CH CH CO),
3
2 3
3
2
þ
.36–1.07 [m, 12H, (CH CH ) NH , CH CH CO]; C NMR (CDCl ):
3 2 3 3 2 3
13
1
d (ppm) 177.6 (EtCO), 162.6, 161.3, 155.9, 155.1, 152.4, 148.6, 148.1,
1
1
7
39.5 (C8G), 124.2 (C5C), 121.2 (Cq), 112.0 (C8C), 110.5 (Cq),
0
0
0
08.8 (C3C), 101.2 (C6C), 90.2 (C1 G), 84.5 (C4 G), 73.5 (C2 G),
0
0
1.0 (C3 G), 65.7 (C5 G), 62.8 (CH OC), 55.7 (MeO), 45.9
2
þ þ
(CH CH ) NH ], 29.7 (CH CH CO), 9.9 [(CH CH ) NH ], 8.7
3 2 3 3 2 3 2 3
[
3
1
(CH CH CO); P NMR (CDCl ): d (ppm) ꢂ0.50.
3
2
3
Triethylammonium (7-Methoxy-4-oxo-4H-chromen-3-yl)methyl 2-N-
0
Propionyl-guanosine 5 -Phosphate (8b)
As above, 7b (220 mg, 0.29 mmol) in formic acid (1.35 mL) led to 168 mg
(
81%) of compound 8b. R ¼ 0.30 (CH Cl =MeOH: 80=20); MS (ESIþ ,
þ þ
3
f
2
2
20
D
m=z): 709 [M þ H] , (ESI ꢂ , m=z): 606 [M– Et NH ]; ½aꢃ ꢂ 51 (c 1.0,
1
CH Cl ); H NMR (CDCl ): d (ppm) 8.00–7.91 (m, 3H, 8G-H, 5C-H,
2
2
3
2
1
1
4
C-H), 6.91 (dd, 1H, J ¼ 8.9 Hz, J ¼ 2.0 Hz, 6C-H), 6.78 (d,
6
,8
4
0
H, J ¼ 1.9 Hz, 8C-H), 5.84 (d, 1H, J
0
0
¼ 5.8 Hz, 1 G-H), 4.89 (tl,
6
,8
1 ,2
0
H, J1
.62–4.60 (m, 1H, 3 G-H), 4.25–4.23 (m, 3H, 4 G-H, 5 G-H), 3.88 (s, 3H,
0
0
¼ J
0
0
¼ 5.3 Hz, 2 G-H), 4.81 (d, 2H, J
¼ 7.0 Hz, CH OC),
,2
2 ,3
CH2,P
2
0
0
0
þ
CH OC), 2.84 [q, 6H, J ¼ 7.2 Hz, (CH CH ) NH ], 2.55 (q, 2H,
3
3
2 3
J ¼ 7.2 Hz,
CH CH CO),
3
1.26–1.09
[m,
12H,
CH CH CO,
3 2
2
þ
13
(
(
CH CH ) NH ]; C NMR (CDCl ): d (ppm) 177.9 (C4C), 176.1
3 2 3 3
EtCO), 164.1 (Cq), 158.3 (Cq), 156.0 (Cq), 153.9 (C2C), 148.7 (Cq),

0
(
Chromenonyl)methyl Guanosine 5 -Phosphates
471
1
1
48.2 (Cq), 140.0 (C8G), 126.8 (C5C), 121.2 (Cq), 121.1 (Cq), 117.5 (Cq),
0
0
0
14.9 (C6C), 100.2 (C8C), 90.3 (C1 G), 84.9 (C4 G), 73.9 (C2 G), 71.1
0
0
(
NH ], 29.8 (CH CH CO), 8.9 [CH CH CO, (CH CH ) NH ];
C3 G), 66.0 (C5 G), 59.8 (CH OC), 55.9 (CH OC), 45.8 [(CH CH )
þ
2
3
3
2 3
þ
3
2
3
2
3
2 3
3
1
P NMR (CDCl ): d (ppm) ꢂ0.3.
3
Triethylammonium (7-Methoxy-4-oxo-4H-chromen-2-yl)methyl 2-N-
0
Propionyl-guanosine 5 -Phosphate (8c)
A for 8a, 370 mg (0.5 mmol) of substrate 7c in formic acid (2 mL) led to
37 mg (68%) of compound 8c. R ¼ 0.22 (CH Cl =MeOH: 80=20); MS
2
f
20
D
2
2
þ
(
3
ESI þ , m=z): 709 [M þ H] , ½aꢃ ꢂ 14.2 (c 1.0, MeOH); IR (neat)
ꢂ1
1
202 (OH), 2988 (Ar), 2938, 1679, 1610 (C¼O) cm ; H NMR (CDCl ):
3
d (ppm) 12.2 (bs, 1H, NH), 8.60 (s, 1H, NH), 7.97 (d, J ¼ 10 Hz, 1H, 5C-
H), 7.87 (s, 1H, 8G-H), 6.89 (d, J ¼ 10 Hz, 1H, 6C-H), 6.73 (d, J ¼ 2.5 Hz,
0
1
1
4
H, 8C-H), 6.38 (s, 1H, 3C-H), 5.84 (d, J ¼ 2.5 Hz, 1H, 1 G-H), 5.03 (bs,
0
0
H, 2 G-H), 4.75–4.73 (bt, J ¼ 5 Hz, 2H, CH OC), 4.63 (bs, 1H, 3 G-H),
2
0
0
.27 (bs, 3H, 3H, 4 G-H 5 G-H), 3.88 (s, 3H, ꢂOCH ), 3.05 [q,
,
3
þ
J ¼ 7.5 Hz, 6H, (CH CH ) NH ], 2.52 (q, J ¼ 6.3 Hz, 2H, CH CH CO),
3
2 3
3
2
þ
1
.26 [t, J ¼ 7.5 Hz, 9H, (CH CH ) NH ], 1.08 (q, J ¼ 6.3 Hz, 3H,
3 2 3
3
2 3
3
1
CH CH CO); P NMR (CDCl ): d (ppm) ꢂ0.67.
Triethylammonium (7-Methoxy-2-oxo-2H-chromen-4-yl)methyl
0
Guanosine 5 -Phosphate (1a)
A mixture of compound 8a (65 mg, 0.09 mmol) and 0.7 mL of 1 M aque-
ous sodium hydroxide solution was stirred at room temperature for 15 h
þ
and then neutralized with Amberlite IR-120 (H ) resin. Stirring was con-
tinued for 15 min before filtration and concentration to dryness under
vacuum. Triethylamine (1 mL) was added to the residue dissolved in
water, then concentrated to dryness under vacuum. The final residue
was subjected to purification by column chromatography (CH Cl =
2
2
MeOH=Et N: 80=20=0.2) to give foamy 1a (59 mg, 98%). R ¼ 0.13
3
f
þ
1
(
CH Cl =MeOH: 70=30); MS (ESIꢂ , m=z) ¼ 550 [M–Et NH ];
H
2
2
3
NMR (CDCl ): d (ppm) 7.67 (s, 1H, 8G-H), 6.92 (d, 1H, J ¼ 8.8 Hz,
3
5,6
5
1
C-H),6.63–6.56 (m, 2H, 6C-H6C, 8C-H), 6.20 (bs, 1H, 3C-H), 5.60 (d,
0
H, J1
0
0
0
¼ 5.0 Hz, 1 G-H), 4.71–4.69 (m, 2H, CH OC), 4.56 (appt, 1H,
,2
2
0
0
J1
H), 4.13–4.08 (m, 3H, 4 G-H, 5 G-H), 3.79 (s, 3H, MeO), 3.14 [q, 6H,
0
¼ J
0
0
¼ 5 Hz, 2 G-H), 4.36 (appt, 1H, J
0
0
¼ J
0 0
3 ,4
¼ 5.0 Hz, 3 G-
,2
2 ,3
2 ,3
0
0
þ
þ
J ¼ 7.3 Hz, (CH CH ) NH ], 1.22 [t, 9H, J ¼ 7.3 Hz, (CH CH ) NH ];
3
2 3
3
2 3
1
3
C NMR (CDCl ): d (ppm) 177.4 (C6 ), 164.5 (C2C), 162.6, 158.2,
3
G
1
54.2, 153.6, 151.2, 137.3 (C8G), 124.2 (C5C), 116.3, 112.9 (C8C),

472
E. Faurel-Paul et al.
0 0 0
10.0, 107.1 (C3C), 101.1 (C6C), 87.6 (C1 G), 83.5 (C4 G), 73.3 (C2 G),
1
7
4
0
0
0.1 (C3 G), 66.9 (C5 G), 62.7 (CH OC), 56.1 (CH OC),
2
3
þ
þ
31
7.0 [(CH CH ) NH ], 8.6 [(CH CH ) NH ]; P NMR (101.25 MHz,
3
2 3
3
2 3
CDCl ): d (ppm) þ10.9.
3
Triethylammonium (7-Methoxy-4-oxo-4H-chromen-2-yl)methyl
0
Guanosine 5 -Phosphate (1c)
0
Compound 7 c (227 mg, 0.4 mmol) was converted into 1c (217 mg, 83%)
as described for the preparation of compounds 8. R ¼ 0.16
f
2
D
0
(
MeOH=CH Cl ¼ 30=70); ½aꢃ þ 7.7 (c 0.3, H O); MS (ESI þ ,
2
2
2
þ
1
m=z) ¼ 653 [M þ H] ; IR (neat): 3320 (OH); 3196 (Ar); 2942; 1690,
ꢂ1
1
649 (C=O) cm ; H NMR (D O): d (ppm) 7.76 (s, 1H, 8G-H), 7.49
2
(
8
d, J ¼ 8.9 Hz, 1H, 5C-H), 6.69 (d, J ¼ 8.9 Hz, 1H, 6C-H), 6.47 (s, 1H
0
C-H), 6.14 (s, 1H 3C-H), 5.62 (d, J ¼ 5.0 Hz, 1H, 1 G-H), 4.62–4.58
0
0
(m, 3H,-CH Oc, 2 G-H), 4.28–4.20 (m, 1H, 3 G-H), 4.15–4.08 (m, 3H,
2
0
0
4
GH, 5 G-H), 3.75 (s, 3H, MeO), 3.17 [q, J ¼ 7.5 Hz, 6H,
þ
þ
13
(
(
CH CH ) NH ], 1.25 [t, J ¼ 7.5 Hz, 9H, (CH CH ) NH ]; C NMR
2
3
2 3
3
2 3
D O): d (ppm) 179.5 (C6G), 165.8 (C2C), 165.6, 164.4, 158.2, 157.8,
1
7
53.7, 151.2, 137.1, 126.0, 115.9, 115.2, 108.0, 100.3, 87.4, 83.4, 73.8,
þ
0.3, 65.6 (CH ), 63.4 (CH ), 56.2 (MeO), 47.0 [(CH CH ) NH ], 8.6
2 3
2
2
3
þ
31
[
(CH CH ) NH ]; P NMR (CDCl ): d (ppm) þ11.0.
3
2 3
3
ACKNOWLEDGMENTS
E F.-P. is grateful to Ecole Doctorale du M e´ dicament (EDM) for a three-
year doctoral fellowship. K.Y., a visiting student at Paris Descartes in
2
007, is grateful both to the University of Okayama (from Pr. H.
0
Tanaka s group at School of Engineering) for a leave of absence and to
Paris Descartes University (Service des Relations Internationales) for
partial financial support during his stay in Paris. The authors also
acknowledge funding from the French Centre National de la Recherche
Scientifique (CNRS) and Paris Descartes University.
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