Nucleoside 5′-C-phosphonates: reactivity of the α-hydroxyphosphonate moiety

Article abstract of DOI:10.1016/j.tet.2006.03.008

We found that various dialkyl phosphites, dialkyl trimethylsilyl phosphites, and tris-trimethylsilyl phosphite reacted smoothly with nucleoside 5′-aldehydes to afford epimeric nucleoside 5′-C-phosphonates in high yields. A number of these compounds in bot

Full text of DOI:10.1016/j.tet.2006.03.008

Tetrahedron 62 (2006) 4917–4932
Nucleoside 50-C-phosphonates: reactivity of the
a-hydroxyphosphonate moiety
ˇ
Sarka Kralıkova, Milos Budesınky, Milena Masojıdkova and Ivan Rosenberg
*
´
ˇ
ˇˇ´
´
ꢀ
ꢀ
ꢀ
´
ꢀ
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague 6, Czech Republic
Received 20 October 2005; revised 12 February 2006; accepted 2 March 2006
Available online 31 March 2006
Abstract—We found that various dialkyl phosphites, dialkyl trimethylsilyl phosphites, and tris-trimethylsilyl phosphite reacted smoothly
with nucleoside 50-aldehydes to afford epimeric nucleoside 50-C-phosphonates in high yields. A number of these compounds in both the
20-deoxyribo and ribo series were prepared. In the case of 20-deoxythymidine-50-aldehyde, a thorough study was made on the influence of
the 30-hydroxyl protecting group, type of phosphite, base, and solvent, on the yield and epimeric ratio of the resulting 50-hydroxyphospho-
nates. Partial stereoselectivity in favour of either R or S epimers was observed. An attempt to transform the a-hydroxyl of the phosphonate
moiety into a halo or azido moiety was not successful. Only intramolecular substitution reaction of the mesyloxy group for an alkoxy residue
of the 2-hydroxyethyl ester took place in a low yield.
Ó 2006 Elsevier Ltd. All rights reserved.
HO
B
B
HO
B
RO
1. Introduction
O
O
OH
O
OH
HO
Nucleoside phosphonic acids, the well-known structurally
diverse analogues of natural nucleotides, exhibit virtually ab-
solute stability against enzymes of nucleotide catabolism,
such as phosphomonoesterases and nucleotidases.1 Among
them, several types exhibit, after in vivo phosphorylation,
remarkable antiviral properties.2 The potential biological
effects of nucleoside phosphonic acids have been the driving
force in the search for novel nucleotide analogues with the
P–C linkage. Nucleoside a-hydroxyphosphonic acids
bearing a phosphoryl moiety attached directly to one of the
carbon atoms of the sugar ring could undoubtedly be interest-
HO P(OR')2
(R'O)2P OH
(R'O)2P
3
O
O
1
O 2
HO
(HO)2P
HO
B
C
B
(HO)2P
O
O
HO
O
(HO)2P
O
O
O
RO R'' (H, OR)
HO
HO OH
4b
5
4a
Figure 1. Examples of isopolar non-isosteric nucleoside phosphonic acids.
Herein, we present the synthesis of a number of nucleoside
50-C-phosphonates (50-hydroxyphosphonates) in 20-deoxy-
ribo 12–15 and ribo series 48–53 bearing an additional chiral
centre on the C50 atom (Schemes 1 and 4, Tables 1 and 3),
and demonstrate the reactivity of the 50-hydroxy group of
the hydroxyphosphonate moiety. We prepared these com-
pounds employing the general method of nucleophilic addi-
tion of phosphites to carbonyl compounds.9–11 We found it
interesting to subject these compounds to further transfor-
mation reactions to obtain a variety of new derivatives. In ad-
dition, the free nucleoside 50-C-phosphonic acids 38–41 and
54–58 represent a pool of potential antimetabolites which
could inhibit, for instance, different mammalian 50-nucleo-
tidases, as described earlier12 for another type of nucleoside
50-phosphonic acids prepared in our laboratory.13,14 Also the
inhibition of thymidine phosphorylase, the enzyme involved
in angiogenesis,15 by nucleoside 50-C-phosphonic acids
could be expected, similarly to recently reported case of acy-
clic nucleoside phosphonic acids.16
3
ꢀ
ꢀ4
´
ing compounds in this respect. Wiemer and Kralıkova re-
ported 30- and 20-a-hydroxyphosphonate derivatives of
nucleosides (Fig. 1). These 20- and 30-nucleotide analogues,
however, did not exhibit any antiviral properties. A short ac-
count on the synthesis of regioisomeric compounds bearing
the 50-hydroxyphosphonate moiety 4a was also reported by
´
Recently Wiemer7 described the synthesis
ꢀ
ꢀ 5,6
Kralıkova.
of arabinosylcytosine 50-hydroxyphosphonate 4b which
showed interesting biochemical properties. The nucleoside
50-hydroxyphosphonates are related to the known 50-deoxy-
nucleoside 50-phosphonates8 5 that lack chirality on the C50
atom (Fig. 1).
Keywords: Nucleoside 50-aldehydes; Oxidation; Phosphonates; Addition
reaction; Nucleophilic substitution.
* Corresponding author. Tel.: +420 220 183 381; fax: +420 220 183 578;
e-mail: ivan@uochb.cas.cz
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.03.008

ˇ
S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4918
HO
(HO)2P
HO
(R'O)2P
O
B
B
B
B
HO
O
O
O
O
O
i
ii
iii
O
HO
RO
RO
12-15
RO
11
6-9
38 B=T (from 12c)
39 B=C (from 13)
40 B=G (from 14b)
41 B=A (from 15b)
For B, R, R' and more details see Table 1
iv
O
N
O
O
CH3
CH3
CH3
N
N
N
HO
O
O
O
N
N
HO
O
O
O
O
v
vi
(MeO)2P
O
10
10a
16
Scheme 1. (i) DMSO–(COCl)2 or DMSO–DCC method; (ii) (R0O)2(O)PH, Et3N; (iii) (a) Me3SiBr, CH3CN, 24 h, rt, (b) satd ammonia in 50% aq ethanol, 48 h,
rt, (c) 1 M TBAF in THF, 16 h, rt; (iv) Ph3P, DEAD (from 10 R¼H, B¼T); (v) DMSO, DCC, pyridine, TFA; (vi) (MeO)2(O)PH, Et3N.
Table 1. Epimeric ratios and yields of prepared 20-deoxynucleoside 50-C-phosphonates (for general structures see Scheme 1)
Starting nucleoside
Oxidation method
Ac
Phosphite
Product
B
T
R
R0
R/S ratioa
Yield %b
6a
(Me3SiO)3P
(MeO)2POH
(EtO)2POH
(iPrO)2POH
(MeO)2POH
(MeO)2POH
(EtO)2POH
(EtO)2POH
(MeO)2POH
(MeO)2POH
12a
12b
12c
12d
12e
12f
12g
12h
12i
TBDPS
H
Me
Et
iPr
Me
Me
Et
Et
Me
Me
37/63
21/79
19/81
13/87
20/80
42/58
50/50
33/67
19/81
15/85
34/66
40/60
25/75
22/78
37/63
85
78
77
67
71
52
58
54
60
84
82
76
69
80
34
6b
6c
TBDMS
Bz
Bd
Ac
Bd
6d
6e
7
8a
8b
9a
9b
10
Piv
DMTr
TBDPS
13
CBz
GBz
GiBu
ABz
ABz
T
14a
14b
15a
15b
16
DMTr
—
—
Epimeric ratio determined from 1H NMR spectra.
Isolated yield.
DMSO–(COCl)2.
a
b
c
d
DMSO–DCC–pyridine–TFA.
2. Results and discussion
changing several factors, such as the solvent and the base
used, and the type of phosphorus acid esters. We found
that the solvent did not have any effect on the stereoselectiv-
ity, but the yields of phosphonates were different. Thus,
DCM provided better yields of 50-C-phosphonates than
THF and acetonitrile. Increasing the amount of triethyl-
amine (from 1 to 5 equiv) or the use of saturated ammonia
in dioxane as a weak base did not influence the ratio of epi-
mers. The use of DBU instead of triethylamine caused de-
struction of the starting nucleoside 50-aldehyde. No change
in the ratio of the epimeric phosphonates under the addition
of diethyl phosphite in the presence of either lithium bis
(trimethylsilyl)amide or tert-butylmagnesium chloride at
2.1. Preparation of 20-deoxyribonucleoside 50-C-
phosphonates
The synthesis of protected nucleoside hydroxyphosphonates
12–16 in the 20-deoxy series was accomplished by nu-
cleophilic addition of various phosphites to nucleoside
50-aldehydes 11 and 10a (Scheme 1, Table 1) obtained by ox-
idation of protected nucleosides 6–9, 10 using the Swern
(DMSO–(COCl)2)17 or modified18 Moffatt procedures
(DMSO–DCC).19,20 They were used in further reaction
without purification and characterization. Whereas the 30-
O-silyl-protected 20-deoxyribonucleosides 6a, 6b, 7, 8a, 8b
and 9a were smoothly oxidized by the Swern procedure17
(Method A), for the oxidation of 20-deoxynucleosides bear-
ing 30-O-acyl protecting groups 6c, 6d, 30-O-DMTr deriva-
tives 6e and 9b, and 2,30-anhydrothymidine (10) the
DMSO–DCC method18 was used (Method B) (Table 1). In
ꢁ
ꢀ78 C was found, but the yields of 50-C-phosphonates
were significantly reduced. On the other hand, only little
changes in epimeric ratios were found if various dialkyl
phosphites were used in the presence of triethylamine (Table
1); however, tris-trimethylsilyl phosphite exhibited signifi-
cantly lower stereoselectivity in the addition reaction. The
comparison of various types of 30-O-protecting groups re-
vealed (Table 1) that the use of 30-O-acyl groups resulted
in decrease of reaction preferences for the (S)-epimers.
17
contrast to literature data, the 30-O-acyl-protected 20-de-
oxynucleosides 6c and 6d were not stable under conditions
of the Swern oxidation procedure.17
We attempted to increase the stereoselectivity of the addition
of dialkyl phosphites to nucleoside 50-aldehydes (Table 1) by
The epimeric, protected nucleoside 50-C-phosphonates 12–
15 were separable by RP-HPLC, but on silica gel the

ˇ
S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4919
separation seldom took place. During our experiments, we
succeeded in the separation of the epimers of dimethyl-(2-
N-benzoyl-30-O-tert-butyldiphenylsilyl-20-deoxyguanosin-50-
C-yl-phosphonate) (14a) on C18 silica. In case of thymidine
phosphonate 12, we examined several ways in which to sep-
arate individual epimers. We found that removal of the 30-O-
protecting group of dimethyl phosphonates 12b and 12f
resulted in better resolution of epimers on C18 silica. Unfor-
tunately, hydrolysis of the silyl or benzoyl 30-O-protecting
group was accompanied by partial hydrolysis of one methyl
ester group (epimeric monomethyl esters were very difficult
to separate). In addition, the removal of 30-O-benzoyl group
from phosphonate 12f led to the change of elution order of
epimers on silica gel (not on C18 silica), and to significant
increase of DRf of epimers on TLC. In the case of di-
methyl-(30-O-tert-butyldimethylsilyl-20-deoxythymidin-50-C-
yl-phosphonate) (12e), we succeeded in the separation of the
substantial part of minor (R)-epimer by crystallization from
ethyl acetate–ethanol mixture. Likewise, crystallization of
the epimeric mixture of dimethyl-(30-O-benzoyl-20-deoxy-
thymidinyl-50-C-phosphonate) (12f) provided the major
(S)-epimer.
Lower values of J(P,H40) and J(H40,H50) were observed for
major isomer in five-epimeric pairs 12–15, 25–26 and 54–
58, indicating the 50(S)-configuration for the major isomer,
similar to the above discussed pair 14a, 14b. It should be
noted that this relation between J(P,H40) and J(H40,H50) in
the 50(S) and 50(R) isomers does not hold in general for all
nucleotides studied in this paper. For example, in depro-
tected epimeric pairs 38–41 and/or in 2,3-di-O-isopropyli-
dene derivatives 48–53 prepared from precursors with
known ratio of 50(S) and 50(R) isomer, the observed relative
values of corresponding J(H,H) are opposite. A similar situ-
ation was also found in nucleosides 16 and 36, obviously due
to the different preferred conformation around the C40–C50
bond in the presence of additional sugar ring.
2.3. Attempt to convert a-hydroxyphosphonate moiety
into a-halophosphonate ( Scheme 2)
Reaction of the 50-hydroxyl of 12b with CBr4 or CCl4 and tri-
phenylphosphine in dioxane to prepare a halo derivative 17
failed. Whereas at rt we observed no reaction, under heating
total decomposition of 12b took place. Also the attempt to
obtain fluoro derivative 18 in the reaction of 12b with
2.2. 1H and 13C NMR study
DAST21 in dichloromethane at ꢀ78 C failed, and we iso-
ꢁ
lated only a small amount of product of elimination, namely
1-(3-O-tert-butyldiphenylsilyl-2,5-dideoxy-b-D-glycero-pent-
4-enofuranosyl)thymine. Therefore, on reaction with meth-
ansulfonyl chloride in pyridine, the phosphonate 12b was
first transformed into 50-O-mesyl derivative 19, which was
used for the reaction with TBAF in dimethylformamide in
the presence of powdered molecular sieves. The mesyl
derivative 19 was completely stable at rt, but under heating
provided a mixture of products. The reaction of 19 with
tris(dimethylamino)sulfonium difluorotrimethyl silicate
(TASF)22 in various solvents (dichloromethane, acetonitrile
and dimethylformamide) resulted in quantitative conversion
of 19 into its 3-N-methyl derivative (structure not shown); no
fluoro derivative 18 was formed.
Individual epimers 14a were subjected to NMR analysis to
determine the configuration at the 50-carbon atom. The struc-
tural assignment was carried out using characteristic chemi-
cal shifts (protons and carbons of the nucleobase and
substituents), homonuclear 2D-COSY and 2D-ROESY
1
spectra (deoxyribose protons), and heteronuclear H, 13C-
2D-HMQC spectra (deoxyribose carbon atoms). Vicinal cou-
plings J(H,H) showed a high preference for the C20-endo
form of the deoxyribofuranse ring in both epimers (w85%
in the major andw95% in the minor epimer). The preferred
syn-orientation of the nucleobase was determined from 2D-
ROESY spectra. Determination of the configuration at C50
is closely connected with the conformation around C40–C50
bond. The high value of J(P,C30)¼14.6 Hz and low value of
J(P,H40)¼2.3 Hz in the major epimer indicates the trans-ar-
rangement of P and C30 which, together with a gauche-rela-
tionship of H40/H50 as indicated by J(H40,H50)¼2.3 Hz,
establishes the (S)-configuration at C50 (Fig. 2). The config-
uration of minor epimer 14a is therefore 50(R) and the set of
its vicinal couplings (J(P,C30)¼8.8 Hz, J(P,H40)¼5.4 Hz and
J(H40,H50)¼6.4 Hz) indicate comparable populations of
trans and gauche conformers around C40–C50 bond (Fig. 2).
2.4. Attempt to convert a-hydroxyphosphonate into
a-azidophosphonate
An attempt to displace the mesyloxy group of adenine deriv-
ative 20 by an azide ion caused only quantitative cleavage of
one methyl ester group giving monomethyl derivative 21
(Scheme 2). We also did not succeed in the preparation of
a more reactive 50-O-trifluoromethanesulfonyl derivative
O
OCH3
O
O
OCH3
O
HO
O
CH3O
H4'
P
CH3O
H4'
P
OCH3
O
H4'
P
OH
H5'
OCH3
H5'
C3'
H5'
C3'
HO
C3'
5'(R)
5'(S)
J(P,C3') = 14.6 Hz
J(P,H4') = 2.3 Hz
J(H4',H5') = 2.3 Hz
J(P,C3') = 8.8 Hz
J(P,H4') = 5.4 Hz
J(H4',H5') = 6.4 Hz
Figure 2. Epimers 14a: preferred conformations around C40–C50 in both epimers and vicinal coupling constants used for determination of the configuration at
carbon C50.

ˇ
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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
F
HO
(MeO)2P
X
T
B
T
O
O
CX4/Ph3P
O
(MeO)2P
DAST
(MeO)2P
O
O
12b B=T
O
13 B=CBz
15a B=ABz
OTBDPS
OTBDPS
18
OTBDPS
17
MsCl
pyridine
TBAF/DMF
or TASF
Ph3P/DIAD/
(PhO)2P(O)N3
O
CH3SO2O
(MeO)2P
N3
O
O
B
B
B
O
O
O
(MeO)2P
(MeO)2P
longer react.
time
O
O
O
19 B=T
22 B=T
25 B=T
26 B=CBz
27 B=ABz
O
OTBDPS
NaN3
OTBDPS
OTBDPS
longer
23 B=CBz
24 B=ABz
20 B=ABz
N
N
PPh3
CH3
react. time
O
O
O
CH3SO2O
O
O
CBz
ABz
O
O
N
HO
RO
O
O
P
P
(MeO)2P
MeO
MeO
O
O
O
28
21
29
OTBDPS
OTBDPS
OTBDPS
N3
N
O
PPh3
CH3
CH3
CH3
N
N
HN
O
N
O
N
O
N
O
O
O
O
O
O
O
O
O
H3C
31 CH3
H3C
H3C
Ph3P/DIAD/
(PhO)2P(O)N3
CH3
32
30
CH3
Scheme 2. Reactions on the 50-hydroxyphosphonate moiety.
intended for use in the reaction with sodium azide. At
ꢀ15 C, the reaction of phosphonate 12b with triflic anhy-
tive 31. Thus, we believe that the newly formed pair of peaks
with higher retention times in the reaction of 12b/25
(Scheme 2) are the 50-epimeric triphenylphosphoranylidene
derivatives 29.
ꢁ
dride did not proceed, whereas at rt total decomposition of
starting compound 12b was observed.
Mitsunobu reaction23 of phosphonates 12b, 13 and 15a with
diphenylphosphoryl azide, diisopropyl azodicarboxylate,
and triphenylphosphine did not provide the expected 50-az-
ido derivatives 22–24 but gave the 50-O-isopropoxycarbonyl
derivatives 25–27 in quantitative yield (Scheme 2). Reaction
proceeded with partial inversion of configuration, as it was
proved in the reaction with both the epimeric mixture and
the individual epimers of compound 12b (for results, see Ta-
ble 2). The formation of carbonates under Mitsunobu condi-
tions was observed by Battaglia24 in case of branched
hydroxy derivatives of dioxolanones. During prolonged re-
action time we observed, in the case of cytosine compound
26, the loss of one methyl ester group under formation of
monoester 28. The calculated molecular mass of 28 corre-
sponded with that of found by HRMS. In addition, the deriv-
ative 25 underwent subsequent reaction on the thymine
residue. We detected (by RP-HPLC) the formation of an-
other pair of peaks with higher retention times than starting
epimers 25. Using 30,50-O-isopropylidene-xylo-thymidine
(30) as a model compound, we proved that the reaction on
the thymine residue led to triphenylphosphoranylidene de-
rivative 32, most probably via 4-azido-2-pyrimidone deriva-
2.5. Intramolecular substitution reaction of 50-O-mesyl
group
The failure of substituting a mesyloxy group for an azido
moiety led us to check the possibility of an intramolecular
nucleophilic substitution reaction. Thus, monomethyl ester
33 prepared by treatment of 19 with aqueous pyridine was
condensed by a phosphotriester method25 with 2-benzoyl-
oxyethanol to give mixed diester 34, which was demethy-
lated in aqueous pyridine to give the 2-benzoyloxyethyl
ester 35 (Scheme 3). This compound underwent a slow intra-
molecular nucleophilic substitution of the 50-O-mesyloxy
group with the hydroxy moiety of the 2-hydroxyethyl ester
residue in refluxing 1 M sodium methoxide in methanol.
After complete removal of the silyl protecting group, RP-
HPLC isolation provided both epimers of cyclic monoester
36a and 36b as well as 2-hydroxyethyl ester 37 in low yields,
along with thymine as the main product.
2.6. Preparation of ribonucleoside 50-C-phosphonates
The synthesis of protected ribonucleoside hydroxyphospho-
nates 48–53 was accomplished by nucleophilic addition of
phosphites to nucleoside 50-aldehydes of general formula
47 obtained by oxidation of protected nucleosides 42–46
using the DMSO–DCC procedure18 (Scheme 4, Table 3).
Again in this case, we observed reaction preferences for
the formation of (S)-epimers (Table 3). Separation of epi-
meric pairs of phosphonates 48–53 was more effective on
C18 silica than on silica gel.
Table 2. Changes of epimeric ratio in the reaction 12b/25 (Scheme 2)
R/S epimeric ratio
Reactant 12b
Product 25
22/78
0/100
100/0
43/57
64/36
17/83

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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4921
CH3SO2O
CH3SO2O
CH3SO2O
T
T
MeO
HO
T
MeO
O
O
O
P
P
P
BzOCH2CH2O
BzOCH2CH2O
HO
O
O
O
iii
ii
i
OTBDPS
OTBDPS
OTBDPS
33
34
35
19
HO O
O
O
P
HO
HO
iv
T
T
T
O
O
O
P
HOCH2CH2O
O
P
O
+
+
O
HO O
(R)
OH
OH
36b
OH
37
(S)
36a
Scheme 3. (i) Aqueous pyridine (60%), 50 ꢁC; (ii) BzOCH2CH2OH, MSNT, 4-methoxypyridine-N-oxide, pyridine; (iii) 60% aq pyridine, 50 ꢁC; (iv) 1 M
CH3ONa in CH3OH, reflux.
HO
(R'O)2P
O
HO
(HO)2P
O
B
HO
B
B
O
B
O
O
O
O
i
ii
iii
O
O
O
O
O
O
HO OH
H3C
CH3
H3C
CH3
H3C
CH3
54 B=UMeM (from 48)
55 B=U (from 49)
56 B=C (from 50)
57 B=G (from 51)
42-46
47
48-53
For B, R' and more details see Table 3
58 B=A
(from 52)
Scheme 4. (i) DCC–DMSO (Method B); (ii) (R0O)2(O)PH, Et3N; (iii) (a) Me3SiBr, CH3CN, 24 h, rt, (b) concd aq ammonia, 48 h, rt, (c) 0.025 M H2SO4 in 50%
aq dioxane, 16 h, rt.
Table 3. Epimeric ratios and yields of prepared ribonucleoside 50-C-phosphonates (for general structure see Scheme 4)
Starting nucleoside
Oxidation method
Bc
Phosphite
Product
B
R0
Et
R/S ratioa
Yield %b
42
43
44
45
46
(EtO)2POH
48
49
50
51
52
53
UMeM
U
30/70
45/55
43/57
40/60
33/67
17/83
31
46
57
66
32
42
CBz
GBz
ABz
ABz
(MeO)2POH
(EtO)2POH
(MeO)2POH
Me
Et
Me
Epimeric ratio determined from 1H NMR spectra.
Isolated yield.
DMSO–DCC–pyridine–TFA.
a
b
c
Therefore, we examined the nucleosidation reaction as a po-
tential synthetic route for the preparation of pure epimers of
ribonucleoside 50-C-phosphonates (Scheme 5). The starting
sugar-phosphonate synthons (S)-60 and (R)-60 (Scheme 5)
were easily available by addition of diethyl phosphite to 3-
O-benzoyl-1,2-O-isopropylidene-a-D-ribo-pentodialdo-1,4-
furanose according to a modified Otmar procedure.26 Both
epimers were separated on silica gel. The 50-hydroxyl of
these compounds was acetylated in pyridine with acetic an-
hydride, and acetyl derivatives (S)-61 and (R)-61 were sub-
jected to acetolysis to obtain sugar-phosphonate synthons
(S)-62 and (R)-62. Surprisingly, only (R)-61 underwent
clean acetolysis with formation of the expected product
(R)-62 which afforded, on a nucleosidation reaction with si-
lylated 6-N-benzoyladenine 63, the phosphonate (R)-64. On
the other hand, acetolysis of compound (S)-61 resulted
unexpectedly in a mixture of products, so that the route
followingnucleosidation reactionwithsilylated6-N-benzoyl-
adenine 63 did not afford any desired nucleoside phospho-
nate. The reason for instability of (S)-62 toward acetolysis
is not clear. The observation that this synthetic route can
provide only (R)-phosphonates led us back to the original
synthetic route. We found that morpholidate derivatives of
epimeric adenine compound 58 exhibited significant differ-
ence in retention times on C18 silica. To identify the (R)-
epimer in an epimeric mixture, we prepared morpholidate
(R)-59 from the free phosphonate (R)-58, morpholine and
DCC.
Deprotection of fully protected nucleoside phosphonates
12b, 13, 14b, 15b and 48–52 was performed as follows.
First, the alkyl ester groups of the phosphorus moiety were
removed by treatment with bromotrimethylsilane (DMTr
group of 15b was also cleaved off under these conditions),
then N- and O-acyl protected groups were removed in concd
aq ammonia–ethanol mixture and, finally, either silyl groups
were removed by treatment with TBAF in THF or the isopro-
pylidene groups were hydrolyzed in 0.025–0.05 M sulfuric
acid. Free phosphonic acids 38–41 and 54–58 were purified
on DEAE-Sephadex column followed by RP-HPLC. Ob-
tained compounds were transformed into sodium salts on
Dowex 50 (Na+), and finally freeze-dried from water.

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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4922
(EtO)2(O)P
H
OH
O
(EtO)2(O)P
H
OAc
O
(EtO)2(O)P
H
OAc
O
iii
ii
OAc
O
O
BzO
O
BzO
O
BzO OAc
(S)-60
(S)-61
(S)-62
i
1,2:5,6-di-O-isopropylidene-a-D-allofuranose
i
H
OH
O
H
OAc
O
H
OAc
O
(EtO)2(O)P
(EtO)2(O)P
(EtO)2(O)P
OAc
ii
iii
O
O
BzO
O
BzO
O
BzO OAc
(R)-60
(R)-61
(R)-62
NHCOC6H5
O
N
N
H
N
N
H
OH
O
H
OAc
O
OH
O
ABz
A
A
N
(HO)2P
(EtO)2(O)P
P
63
v
SiMe3
vi
HO
O
O
iv
HO OH
(R)-58
BzO OAc
(R)-64
HO OH
(R)-59
Scheme 5. (i) (a) Benzoyl cyanide, Et3N, DCM–acetonitrile, (b) 60% aq acetic acid, 50 ꢁC, (c) NaIO4, 70% aq acetone; (ii) Ac2O, pyridine; (iii) Ac2O, AcOH,
DCM, H2SO4; (iv) SnCl4, acetonitrile; (v) (a) concd aq ammonia–ethanol mixture, (b) Me3SiBr, acetonitrile; (vi) DCC, morpholine, t-BuOH–H2O, reflux.
ꢁ
2.7. Biological properties
70 C and 13 Pa. The course of the reactions was checked
by TLC cards (Fluka, Merck) whereby the products were de-
tected by UV monitoring and by spraying with 1% ethanolic
solution of 4-(4-nitrobenzyl)pyridine followed by heating
and treating with gaseous ammonia (blue colour of diesters
of phosphonic acids). For flash column chromatography, sil-
ica gel 40–60 mm (Fluka) was used. The TLC and the prepar-
ative silica gel chromatography were carried out in the
following solvent systems (v/v): chloroform–ethanol 9/1
(C1); ethyl acetate–acetone–ethanol–water 4/1/1/1 (H1);
ethyl acetate–acetone–ethanol–water 6/1/1/1 (H3); 2-propa-
nol–concd aq ammonia–water 7/1/2 (I); 50% EtOAc–
toluene (T1), 20% EtOAc–toluene (T2). Analytical HPLC
was performed on Nucleosil 100–5 C18 (4.6ꢂ150 mm;
Macharey–Nagel) using a linear gradient of methanol in
0.1 M TEAA. Preparative reversed-phase chromatography
was carried out on octadecyl silica column (25ꢂ250 mm,
20 mm, IOCB Prague); compounds were eluted with a linear
gradient of methanol in water at 15 ml/min. UV spectra and
thermal characteristics were taken on a Cary Bio 100 (Var-
ian) spectrophotometer. High resolution FAB mass spectra
were recorded on a ZAB-EQ (VG Analytical) instrument
with glycerol and thioglycerol as matrices. NMR spectra
were measured on a Varian UNITY-500 spectrometer (1H
at 500 MHz; 13C ꢁat 125.7 MHz frequency) in DMSO-d6
and/or D2O at 20 C. The chemical shifts were referenced
either to solvent signal (converted to d scale using relations
dH(DMSO)¼2.50 and dC(DMSO)¼39.7 ppm) or to DSS (in
D2O). Proton 2D-COSY spectra were used for the structural
assignment of coupled protons and 2D-ROESY spectra for
detection of the NOE contacts. Carbon-13 chemical shifts
and coupling constants J(C,P) were obtained from broad
band proton-decoupled spectra using APT pulse sequence.
Cytostatic activity of protected phosphonates and free phos-
phonic acids was examined on L 1210, L 929 and HeLa S3
cell lines. Antiviral properties of the same compounds were
examined on HIV-1, HIV-2 and Moloney sarcoma virus
(MSV), and on the selected DNA viruses (HSV-1 (KOS),
HSV-1 (B), HSV-1 (McIntyre), HSV-2 (G), HSV-2 (196),
HSV-2 (Lyons), VV, VSV, HSV-1 TKꢀ (B2006) and HSV-1
TKꢀ (VMW1837)). Neither phosphonates 12–15 and 48–53
nor phosphonic acids 38–41 and 54–58 exhibited any sig-
nificant cytostatic and/or antiviral activities.
3. Conclusion
We have established an efficient synthesis of nucleoside 50-
C-phosphonates in 20-deoxyribo and ribo series bearing
a new centre of chirality on the C50 atom via base-catalyzed
nucleophilic addition of various phosphites to nucleoside 50-
aldehydes, and thus enlarged the family of enzyme-stable
nucleotide analogues. The reactivity of 50-hydroxyl of the
nucleoside 50-hydroxyphosphonates was found to be very
specific, and the conversion of the hydroxyl into a halo or az-
ido moiety failed. Only acylation and sulfonylation reactions
proceeded smoothly in quantitative yields. The prepared nu-
cleoside phosphonic acids offer the possibility for their fur-
ther evaluation as inhibitors of mammalian 50-nucleotidases,
bisubstrate inhibitors of thymidine and purine nucleoside
phosphorylases, and, after transformation into nucleoside
50-triphosphate analogues, as substrates/inhibitors of DNA
and RNA polymerases.
4. Experimental
4.1. General
Method A: Swern oxidation procedure [DMSO–(COCl)2].17
Dimethylsulfoxide (0.21 ml, 3 mmol) was added dropwise
to a stirred solution of oxalyl chloridꢁe (0.13 ml, 1.5 mmol)
in dichloromethane (3.5 ml) at ꢀ78 C under argon atmo-
sphere. After 10 min, a solution of protected nucleoside
(1 mmol) (see Table 1) in dichloromethane (7 ml) was added
ꢁ
The solvents were evaporated at 40 C and 2 kPa, and the
products were dried over phosphorus pentoxide at 50–

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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4923
ꢁ
dropwise and the reaction mixture was stirred at ꢀ78 C for
30 min. The reaction was quenched by addition of triethyl-
amine (0.7 ml, 5 mmol). The resulting suspension was
stirred for additional 5 min at low temperature, allowed to
warm to rt, and the appropriate phosphite (2 mmol) (see Ta-
ble 1) was added. The reaction mixture was set aside over-
night at rt (TLC in C-1), diluted with chloroform,
extracted with water, and dried over anhydrous sodium sul-
fate. Chromatography of the crude product on a silica gel
(elution with a linear gradient of 0–10% ethanol in chloro-
form) afforded the desired phosphonate (Table 1).
was stirred for 24 h at rt under exclusion of moisture. In case
of less soluble compounds, an equal volume of pyridine was
added, and the solution was concentrated to half volume.
Silyl group cleavage ability of TBAF in pyridine was at least
as efficient as in THF alone. After removal of the silyl group
(TLC in H-1 and I), water was added to the reaction mixture,
the solution was concentrated in vacuo, and finally Dowex
50 (Et3NH+, 20 ml/mmol) in 50% aqueous ethanol (50 ml/
mmol) was added to remove tetra-n-butylammonium cat-
ions. The suspension was filtered, the resin was washed
with 50% aqueous ethanol, and the combined filtrates were
evaporated. Crude phosphonic acids 38–40 were subjected
to final purification step (Method G).
Method B: Modified Moffatt oxidation procedure [DMSO–
DCC].18 Pyridine (0.08 ml, 1 mmol) followed by TFA
(0.04 ml, 0.5 mmol) was added at rt to a stirred solution of
protected nucleoside (1 mmol) (Tables 1 and 3) and DCC
(0.64 g, 3 mmol) in DMSO (4 ml). After 16 h, appropriate
phosphite (2 mmol) (Tables 1 and 3) and triethylamine
(0.7 ml, 5 mmol) were added and the mixture was stirred
for further 16 h (TLC in C-1). The reaction mixture was di-
luted with chloroform, filtered through Celite, and the filtrate
was extracted with water and organic layer was dried over
anhydrous sodium sulfate. Chromatography of the crude
product on silica gel (elution with a linear gradient of
0–10% ethanol in chloroform) afforded the expected phos-
phonate (Tables 1 and 3).
Method F: Removal of 20,30-O-isopropylidene protecting
group. The products 50–52 (B¼C, G, A; R0¼H) obtained
by Method D were dissolved in aqueous 0.05 M sulfuric
acid (100 ml/mmol) and the solution was set aside overnight
at rt (TLC in H-1 and I). Solution of crude cytidine 56, gua-
nosine 57, and adenosine 58 phosphonic acids was applied
onto a column of Dowex 50 (H+) and, after washing with wa-
ter, the product was eluted by 3% aqueous ammonia. In the
case of uridine derivatives 48 and 49 (B¼UMeM, U; R0¼H)
obtained by Method C, the cleavage of isopropylidene group
ꢁ
was achieved with aqueous 80% acetic acid at 80 C for 3 h.
The reaction mixture was concentrated, and the residue
co-distilled several times with water. The obtained crude
products 54–58 were subjected to final purification step
(Method G).
Method C: Removal of ester protecting groups of phospho-
nate moiety. 2,6-Lutidine (0.58 ml, 5 mmol) and bromotri-
methylsilane (0.66 ml, 5 mmol) were sequentially added to
a solution of phosphonate diester 12c, 13, 14b, 15b, 48–52
(1 mmol) in acetonitrile (5 ml), the mixture was set aside
at rt for 48 h (TLC in C-1, H-1 and I), and then concentrated
in vacuo. Aqueous 2 M TEAB (2 ml) was added, the solution
was concentrated, and the residue was co-distilled several
times with methanol to destroy TEAB and finally with eth-
anol. The obtained N- and/or O-protected nucleoside phos-
phonic acids 12–15 (R0¼H) and 48–52 (R0¼H) were
subjected to further deprotection steps (Method D, E or F).
Method G: Final purification of nucleoside phosphonic
acids. Phosphonic acids 38–41 and 54–58 were purified by
chromatography on DEAE-Sephadex A-25 (HCOꢀ3 ). The
compounds were eluted by a linear gradient of 0–0.2 M
TEAB. Fractions were pooled and evaporated, the residue
was co-distilled several times with methanol and then ap-
plied onto C18 column (25ꢂ300 mm) in a solution of aque-
ous 2 M TEAB (10 ml/mmol). The products were eluted by
a linear gradient of methanol in water (0–10%), then trans-
formed into sodium salts on a column of Dowex 50 (Na+),
and finally freeze-dried from water.
Method D: Removal of N-protecting groups. The solution or
suspension of N-protected cytosine- (13 and 50, R0¼H), gua-
nine- (14 and 51, R0¼H) and adenine-containing (15 and 52,
R0¼H) phosphonic acid, obtained by Method C, in methanol
or ethanol (50 ml/mmol) was saturated with gaseous ammo-
4.1.1. 30-O-tert-Butyldiphenylsilyl-20-deoxythymidin-50-
C-ylphosphonic acid (12a). Phosphonate 12a was obtained
from tris(trimethylsilyl) phosphite (1.0 ml, 3 mmol) and the
aldehyde prepared from 30-O-tert-butyldiphenylsilyl-20-de-
oxythymidine27 (480 mg, 1 mmol) according to Method A.
The reaction was quenched by addition of methanol (5 ml)
andꢁ 2 M TEAB (5 ml), and the solution was heated at
80 C for 2 h (TLC in H1). After evaporation of the solvent,
the partially protected phosphonate was purified on RP C18
column (elution with a linear gradient of methanol in water).
Yield, 562 mg (85%; white foam) of triethylammonium salt
of 12a (R/S 37/63). For C26H33N2NaO8PSi (M+Na)+ calcd:
583.1643, found: 583.1642. 1H NMR—see Tables 4 and 5.
ꢁ
nia at 0 C. The mixture was stirred in a tightly stoppered
flask at rt overnight (TLC in C-1, H-1 and I). Deprotection
of N-benzoylguanine derivatives 14 and 51 (R0¼H) took
ꢁ
place in an autoclave at 60 C overnight. Alternatively, de-
acylations were also performed in a 1/1 mixture of concd
aq ammonia–ethanol for 16 h with identical results. Solvent
was evaporated, and the residue was dried by co-distillation
with ethanol (3ꢂ20 ml). The crude deacylated compounds
13 and 14 (B¼C, G; R0¼H, R¼TBDPS) were subjected to
treatment according to Method E, derivatives 50–52
(B¼C, G, A; R0¼H) to treatment by Method F, and adenine
phosphonic acid 41 (obtained from 15 (B¼ABz; R¼R0¼H))
to the final purification step (Method G).
4.1.2. Dimethyl-30-O-tert-butyldiphenylsilyl-20-deoxythy-
midin-50-C-ylphosphonate (12b). The title compound 12b
was obtained on reaction of dimethyl phosphite (0.18 ml,
2 mmol) and the aldehyde prepared from 30-O-tert-butyldi-
phenylsilyl-20-deoxythymidine27 (480 mg, 1 mmol) accord-
ing to Method A. Yield, 459 mg (78%; white foam) of 12b
(R/S 21/79). For C28H37N2O8PSi (588.66) calcd: 57.13%
Method E: Removal of silyl protecting group. The silyl deriv-
atives 12–14 (B¼T, C, G; R0¼H, R¼TBDPS) obtained by
Method D were co-distilled with dry toluene, dissolved in
0.5 M TBAF in THF (10 ml/mmol), and the reaction mixture

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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4924
Table 4. 1H chemical shifts of compounds 12–16 in DMSO-d6
Compound
H-10
H-20
H-200
H-30
H-40
H-50
50-OH
Nucleobase
(S)-12aa
6.15
6.20
6.31
6.36
6.31
6.36
6.29
6.35
6.17
6.20
6.31
6.27
6.30
6.26
6.19
6.15
6.27
6.14
6.31
6.36
6.45
6.45
6.36
6.35
6.31
6.39
6.65
6.45
5.78
5.85
1.86
1.85
1.96
1.94
1.96
1.95
1.96
1.95
2.14
2.14
2.33
2.42
2.30–2.50
2.30–2.50
2.23
2.28
1.88
1.61
1.94
2.12
2.51
2.77
2.44
2.70
2.87
2.44
2.55
2.35
2.58
2.52
2.00
1.75
2.16
1.87
2.17
1.86
2.19
1.85
2.06
1.96
2.46
2.35
4.51
4.97
4.46
4.64
4.45
4.69
4.44
4.73
4.49
4.65
5.53
5.73
5.52
5.74
5.23
5.48
4.29
4.37
4.49
4.71
4.60
4.77
4.58
4.75
4.57
4.75
4.43
4.59
5.26
5.23
4.30
4.42
4.09
4.24
4.11
4.26
4.13
4.27
4.02
3.96
4.42
4.37
4.42
4.40
4.17
4.15
3.58
4.37
4.20
4.37
4.17
4.30
4.16
4.29
4.29
4.35
3.64
4.46
4.29
4.34
3.39
3.57
3.46
3.98
3.36
3.92
3.27
3.83
4.12
4.04
4.34
4.26
4.28
4.18
4.09
4.20
3.27
3.89
3.48
4.06
3.50
3.97
3.50
3.92
3.95
4.07
3.32
4.03
3.74
4.02
4.50
4.50
6.07
6.28
5.99
6.26
5.85
6.22
6.21
6.35
6.47
6.45
6.37
6.44
6.23
6.40
5.98
6.10
6.12
6.23
6.08
6.18
6.04
6.16
6.03
6.17
6.19
6.13
6.35
6.01
T: 11.20 (NH), 8.18 (H-6), 1.71 (5-Me)
T: 11.20 (NH), 8.02 (H-6), 1.70 (5-Me)
T: 11.32 (NH), 7.82 (H-6), 1.71 (5-Me)
T: 11.30 (NH), 7.57 (H-6), 1.74 (5-Me)
T: 11.31 (NH), 7.86 (H-6), 1.71 (5-Me)
T: 11.30 (NH), 7.65–7.40 (H-6), 1.74 (5-Me)
T: 11.30 (NH), 7.89 (H-6), 1.71 (5-Me)
T: 11.30 (NH), 7.50–7.40 (H-6), 1.74 (5-Me)
T: 11.30 (NH), 7.88 (H-6), 1.76 (5-Me)
T: 11.33 (NH), 7.64 (H-6), 1.78 (5-Me)
T: 11.36 (NH), 7.97 (H-6), 1.79 (5-Me)
T: 11.37 (NH), 7.68 (H-6), 1.81 (5-Me)
T: 11.36 (NH), 7.98 (H-6), 1.78 (5-Me)
T: 11.35 (NH), 7.68 (H-6), 1.80 (5-Me)
T: 11.36 (NH), 7.93 (H-6), 1.79 (5-Me)
T: 11.36 (NH), 7.64 (H-6), 1.77 (5-Me)
T: 11.30 (NH), 7.85 (H-6), 1.70 (5-Me)
T: 11.26 (NH), 7.52 (H-6), 1.71 (5-Me)
CBz: 11.25 (NH), 8.55, 7.32 (H-5, H-6)
CBz: 11.28 (NH), 8.35, 7.25 (H-5, H-6)
GBz: 12.36, 11.91 (2ꢂNH), 8.27 (H-8)
GBz: 12.35, 11.91 (2ꢂNH), 8.24 (H-8)
GiBu: 12.29, 11.65 (2ꢂNH), 8.22 (H-8)
GiBu: 12.10, 11.65 (2ꢂNH), 8.19 (H-8)
ABz: 11.22 (NH), 8.66, 8.54 (H-2, H-8)
ABz: 11.20 (NH), 8.53, 8.32 (H-2, H-8)
ABz: 11.23 (NH), 8.74, 8.71 (H-2, H-8)
ABz: 11.19 (NH), 8.72, 8.61 (H-2, H-8)
T: 7.58 (H-6), 1.76 (Me)
(R)-12aa
(S)-12ba,b
(R)-12ba,b
(S)-12ca,c
(R)-12ca,c
(S)-12da,d
(R)-12da,d
(S)-12eb,e
(R)-12eb,e
(S)-12fb,f
(R)-12fb,f
(S)-12gc,f
(R)-12gc,f
(S)-12hc,g
(R)-12hc,g
(S)-12ib,h
(R)-12ib,h
(S)-13a,b,i
(R)-13a,b,i
(S)-14aa,b,i
(R)-14aa,b,i
(S)-14ba,b,i
(R)-14ba,b,i
(S)-15aa,b,i
(R)-15aa,b,i
(S)-15bb,h,i
(R)-15bb,h,i
(S)-16b
2.23
2.08
2.09
0.95
2.46
1.93
2.46
2.19
2.44
2.17
2.24
2.14
2.55
1.27
2.50
2.52
(R)-16b
T: 7.56 (H-6), 1.75 (Me)
a
30-OTBDPS: 7.55–7.65 (m, 4H) and 7.36–7.52 (m, 6H) (2ꢂC6H5), 1.07–1.10 (s, 9H, t-Bu).
P(OMe)2: 3.32–3.68 (2ꢂd, 2ꢂ3H).
b
c
d
e
f
P(OEt)2: 3.80–4.10 (m, 4H, 2ꢂP–OCH2), 1.10–1.23 (2ꢂd, 2ꢂCH3).
P(iPr)2: 4.49–4.59 (m, 2H, 2ꢂP–OCH), 1.13, 1.14, 1.20 and 1.21 (4ꢂd, 4ꢂCH3).
30-TBDMS: 0.87 (s, 9H, t-Bu), 0.10 (s, 6H, 2ꢂCH3).
30-OBz: 8.02 (m, 2H, o-ArH), 7.70 (m, 1H, p-ArH) and 7.56 (m, 2H, m-ArH).
30-OPiv: 3.90–4.07 (m, 4H, 2ꢂP–OCH2), 1.17 (s, 9H, 3ꢂCH3).
g
h
i
30-ODMTr: 7.43 (m, 2H), 7.35 (m, 2H) and 7.25 (m, 1H) (C6H5); 7.30 (m, 4H) and, 6.93 (m, 4H) (2ꢂC6H4), 3.74 (s, 6H, 2ꢂOCH3).
NBz: 8.05 (m, 2H, o-ArH), 7.65 (m, 1H, p-ArH) and 7.55 (m, 2H, m-ArH).
C, 6.34% H, 4.76% N; found: 56.78% C, 6.23% H, 4.51% N.
MS (FAB): 589.2 (M+H)+. 1H NMR—see Tables 4 and 5.
aldehyde prepared from 30-O-tert-butyldimethylsilyl-20-de-
oxythymidine28 (356 mg, 1 mmol) according to Method A.
Yield, 330 mg (71%; white solid) of 12e (R/S 20/80). Crys-
tallization of 12e from ethanol–ethyl acetate afforded 55 mg
4.1.3. Diethyl-30-O-tert-butyldiphenylsilyl-20-deoxythy-
midin-50-C-ylphosphonate (12c). Phosphonate 12c was ob-
tained from diethyl phosphite (0.26 ml, 2 mmol) and the
aldehyde prepared from 30-O-tert-butyldiphenylsilyl-20-
deoxythymidine27 (480 mg, 1 mmol) according to Method
A. Yield, 475 mg (77%; white foam) of 12c (R/S 19/81).
For C30H41N2O8SiP (616.72) calcd: 58.43% C, 6.70% H,
4.54% N; found: 58.19% C, 6.67% H, 4.43% N. MS
(FAB): 617.4 (M+H)+. 1H NMR—see Tables 4 and 5.
ꢁ
of single epimer (R)-12e (white crystals), mp 235 C. For
C18H33N2NaO8PSi (M+Na)+ calcd: 487.1642, found:
1
487.1651. H NMR—see Tables 4 and 5. 13C NMR—see
Table 10.
4.1.6. Dimethyl-30-O-benzoyl-20-deoxythymidin-50-C-yl-
phosphonate ((S)-12f). Phosphonate 12f was obtained from
dimethyl phosphite (0.18 ml, 2 mmol) and the aldehyde pre-
pared from 30-O-benzoyl-20-deoxythymidine29 (346 mg,
1 mmol) according to Method B. Yield, 236 mg (52%; white
solid) of 12f (R/S 42/58). Crystallization of 12f from chlo-
4.1.4. Diisopropyl-30-O-tert-butyldiphenylsilyl-20-deoxy-
thymidin-50-C-ylphosphonate (12d). Phosphonate 12d was
obtained from diisopropyl phosphite (0.33 ml, 2 mmol) and
the aldehyde prepared from 30-O-tert-butyldiphenylsilyl-20-
deoxythymidine27 (480 mg, 1 mmol) according to Method
A. Yield, 432 mg (67%; white foam) of 12d (R/S 13/87).
For C32H45N2O8SiP (644.27) calcd: 59.60% C, 7.04% H,
4.35% N; found: 59.97% C, 7.08% H, 4.02% N. MS
(FAB): 645.3 (M+H)+. 1H NMR—see Tables 4 and 5.
roform afforded 100 mg of single epimer (S)-12f (white
ꢁ
+
crystals), mp 224 C. For C19H24N2O9P (M+H) calcd:
455.1219, found: 455.1235. 1H NMR—see Tables 4 and 5.
13C NMR—see Table 10.
4.1.7. Diethyl-30-O-benzoyl-20-deoxythymidin-50-C-yl-
phosphonate (12g). Phosphonate 12g was obtained from
diethyl phosphite (0.26 ml, 2 mmol) and the aldehyde pre-
pared from 30-O-benzoyl-20-deoxythymidine29 (346 mg,
1 mmol) according to Method B. Yield, 280 mg (58%; white
foam) of 12g (R/S 50/50). For C21H27N2O9P (482.44)
4.1.5. Dimethyl-30-O-tert-butyldimethylsilyl-20-deoxythy-
midin-50-C-ylphosphonate (12e). Phosphonate 12e was ob-
tained from dimethyl phosphite (0.18 ml, 2 mmol) and the

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4925
Table 5. 1H coupling constants in compounds 12–16 in DMSO-d6
Compound
10,20
10,200
20,200
20,30
200,30
30,40
1.5
40,50
50,OH
40,P
50,P
P,OH
(S)-12aa
(R)-12aa
(S)-12ba,b
(R)-12ba,b
(S)-12ca,b
(R)-12ca,b
(S)-12da,c
(R)-12da,c
(S)-12ea,b
(R)-12ea,b
(S)-12fa,b
(R)-12fa,b
(S)-12ga,d
(R)-12ga,d
(S)-12ha,d
(R)-12ha,d
(S)-12ia,b
(R)-12ia,b
(S)-13b,e
(R)-13b,e
(S)-14ab
(R)-14ab
(S)-14bb
(R)-14bb
(S)-15ab
(R)-15ab
(S)-15bb
(R)-15bb
(S)-16b
8.8
9.5
9.1
9.7
9.0
9.8
9.0
10.0
8.3
9.8
8.9
8.9
9.0
9.0
7.8
9.3
9.6
10.1
8.3
8.0
8.6
10.0
7.3
8.0
8.6
8.9
8.8
9.8
0.5
2.6
5.4
5.1
5.3
5.1
5.4
5.1
5.4
5.1
5.9
5.1
5.8
6.0
5.9
5.9
7.1
5.6
5.4
5.0
5.4
5.4
6.0
5.5
7.3
5.4
5.6
5.0
6.2
5.4
3.9
2.6
12.9
12.9
13.1
13.2
13.2
12.9
13.2
13.2
13.2
12.9
14.0
14.4
n
5.1
4.4
5.1
4.4
5.1
5.9
5.4
4.4
5.4
4.6
6.1
6.2
6.1
6.1
5.0
6.1
5.7
5.4
5.1
4.5
5.0
4.6
3.4
5.0
4.9
5.6
4.9
5.0
1.8
2.3
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
2.4
1.0
1.5
1.9
1.5
2.0
1.4
1.2
0.5
1.2
1.0
1.0
1.8
<1
3.4
1.0
1.0
1.0
0.5
1.0
2.7
2.3
2.2
3.4
2.0
4.8
1.7
4.6
1.5
4.6
2.4
4.4
2.2
3.8
2.4
3.4
2.0
3.4
0.5
6.0
1.7
4.9
2.3
6.4
2.0
6.5
5.0
5.6
1.5
7.3
9.1
6.2
n
n
4.2
4.9
1.5
4.8
0.5
4.6
0.5
4.6
2.7
3.9
2.5
4.7
0.5
4.0
n
12.7
11.0
12.6
9.8
n
n
1.0
1.7
1.0
1.5
1.0
1.0
1.0
2.4
1.0
1.6
2.2
1.5
2.0
2.0
1.2
0.5
n
6.9
6.8
7.1
6.8
7.1
6.8
7.0
6.8
6.9
6.7
7.1
6.8
7.1
6.8
7.0
7.0
7.1
6.8
7.2
7.2
7.0
6.5
7.3
6.6
8.3
8.6
6.0
7.6
9.0
5.1
9.0
5.1
9.8
5.5
8.8
5.0
8.8
6.7
9.0
7.1
7.8
7.1
10.6
7.0
9.0
6.5
7.2
7.2
8.7
6.5
8.0
7.5
8.3
7.1
6.0
7.6
12.7
10.5
13.4
10.3
12.3
10.0
12.1
10.4
12.2
10.5
n
10.5
13.5
9.2
12.7
9.5
12.4
8.8
8.5
8.5
9.5
9.5
6.6
7.6
n
n
13.2
13.2
13.7
13.2
13.4
13.3
13.4
n
13.2
13.6
13.2
n
n
0.5
n
1.0
1.0
1.4
1.7
4.6
2.3
5.4
1.0
5.0
5.5
5.9
1.0
7.3
6.8
5.5
<1
2.0
1.0
1.0
1.0
1.0
1.0
2.4
2.4
12.9
12.9
n
6.0
10.6
(R)-16b
n¼Unresolved multiplet, J could not be determined.
a
J(6,CH3)¼1.0–1.3 Hz.
b
J(P,OCH3)¼10.0–10.5 Hz.
c
J(CH,CH3)¼6.1–6.3 Hz.
d
J(CH2,CH3)¼7.1.
e
J(5,6)¼7.6 Hz.
calcd: 52.23% C, 5.60% H, 5.80% N; found: 51.83% C,
5.96% H, 5.69% N. MS (FAB): 483.4 (M+H)+. 1H NMR—
see Tables 4 and 5.
of 13 (R/S 15/85). For C34H40N3NaO8PSi (M+Na)+ calcd:
700.2220, found: 700.2228. 1H NMR—see Tables 4 and 5.
4.1.11. Dimethyl-2-N-benzoyl-30-O-tert-butyldiphenyl-
silyl-20-deoxyguanosin-50-C-ylphosphonate (14a). Phos-
phonate 14a was obtained from dimethyl phosphite
(0.18 ml, 2 mmol) and the aldehyde prepared from 2-N-
benzoyl-30-O-tert-butyldiphenylsilyl-20-deoxyguanosine32
(610 mg, 1 mmol) according to Method A. Yield, 589 mg
(82%; white foam) of 14a (R/S 34/66). For C35H41N5O8PSi
4.1.8. Diethyl-30-O-trimethylacetyl-20-deoxythymidin-50-
C-ylphosphonate (12h). Phosphonate 12h was obtained
from diethyl phosphite (0.26 ml, 2 mmol) and the aldehyde
prepared from 20-deoxy-30-O-trimethylacetylthymidine30
(326 mg, 1 mmol) according to Method B. Yield, 250 mg
(54%; white solid) of 12h (R/S 33/67). For C19H31N2O9P
(462.43) calcd: 49.30% C, 6.70% H, 6.05% N; found:
48.92% C, 6.81% H, 5.85% N. MS (FAB): 463.4 (M+H)+.
1H NMR—see Tables 4 and 5.
1
(M+H)+ calcd: 718.2462, found: 718.2461. H NMR—see
Tables 4 and 5. 13C NMR—see Table 10.
4.1.12. Dimethyl-2-N-isobutyryl-30-O-tert-butyldiphenyl-
silyl-20-deoxyguanosin-50-C-ylphosphonate (14b). Phos-
phonate 14b was obtained from dimethyl phosphite
(0.18 ml, 2 mmol) and the aldehyde prepared from 2-N-
isobutyryl-30-O-tert-butyldiphenylsilyl-20-deoxyguanosine32
(562 mg, 1 mmol) according to Method A. Yield, 509 mg
(76%; white foam) of 14b (R/S 40/60). For C32H43N5O8PSi
4.1.9. Dimethyl-30-O-dimethoxytrityl-20-deoxythymidin-
50-C-ylphosphonate (12i). Phosphonate 12i was obtained
from dimethyl phosphite (0.18 ml, 2 mmol) and the alde-
hyde prepared from 20-deoxy-30-O-dimethoxytritylthymi-
dine31 (545 mg, 1 mmol) according to Method B. Yield,
391 mg (60%; yellowish foam) of 12i (R/S 19/81). For
C33H37N2NaO10P (M+Na)+ calcd: 675.2084, found:
675.2078. 1H NMR—see Tables 4 and 5.
1
(M+H)+ calcd: 684.2619, found: 684.2614. H NMR—see
Tables 4 and 5.
4.1.10. Dimethyl-4-N-benzoyl-30-O-tert-butyldiphenyl-
silyl-20-deoxycytidin-50-C-ylphosphonate (13). Phospho-
nate 13 was obtained from dimethyl phosphite (0.18 ml,
2 mmol) and the aldehyde prepared from 4-N-benzoyl-30-O-
tert-butyldiphenylsilyl-20-deoxycytidine32(569 mg,1 mmol)
according to Method A. Yield, 569 mg (84%; white foam)
4.1.13. Dimethyl-6-N-benzoyl-30-O-tert-butyldiphenyl-
silyl-20-deoxyadenosin-50-C-ylphosphonate (15a). Phos-
phonate 15a was obtained from dimethyl phosphite
(0.18 ml, 2 mmol) and the aldehyde prepared from 6-N-
benzoyl-30-O-tert-butyldiphenylsilyl-20-deoxyadenosine33
(594 mg, 1 mmol) according to Method A. Yield, 484 mg

ˇ
S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4926
(69%; white foam) of 15a (R/S 25/75). For C35H41N5O7PSi
(1 ml) and the solution was evaporated. Chromatography
of the residue on silica gel (elution with a linear gradient
of 0–10% ethanol in chloroform) afforded compound 25.
Yield, 453 mg (67%; yellowish foam) of 25 (R/S 43/57).
HR FAB: For C32H44N2O10PSi (M+H)+ calcd: 675.2503,
found: 675.2493. nmax(CHCl3) 3390 (w, NH), 3136 (vvw,
]C–H), 3092 (w, Ph), 3073 (w, Ph), 3052 (w, Ph), 1710
(s, sh, C]O), 1690 (vs, C]O), 1590 (w, Ph), 1489 (w,
Ph), 1428 (m, Ph), 1387 (w, CH3), 1377 (m, CH3), 1364
(m, t-Bu), 1255 (s, P]O), 1041 (s, COPOC), 998 (m, Ph),
1
(M+H)+ calcd: 702.2513, found: 702.2517. H NMR—see
Tables 4 and 5.
4.1.14. Dimethyl-6-N-benzoyl-20-deoxyadenosin-30-O-di-
methoxytrityl-50-C-ylphosphonate (15b). Phosphonate
15b was obtained from dimethyl phosphite (0.18 ml,
2 mmol) and the aldehyde prepared from 6-N-benzoyl-20-
deoxy-30-O-dimethoxytrityladenosine30 (658 mg, 1 mmol)
according to Method B. Yield, 612 mg (80%; yellowish
foam) of 15b (R/S 22/78). For C40H40N5NaO9P (M+Na)+
1
703 (m, Si–O) cmꢀ1. H NMR—see Tables 6 and 7. 13C
1
calcd: 788.2461, found: 788.2460. H NMR—see Tables 4
and 5.
NMR—see Table 10.
4.1.17.
Dimethyl-4-N-benzoyl-30-O-tert-butyldi-
4.1.15. Dimethyl-2,30-anhydro-20-deoxythymidin-50-C-yl-
phosphonate (16). Phosphonate 16 was obtained from di-
methyl phosphite (0.18 ml, 2 mmol) and the aldehyde
prepared from 2,30-anhydro-20-deoxythymidine34 (673 mg,
3 mmol) according to Method B. Yield, 337 mg (34%; white
solid) of 16 (R/S 37/63). For C12H18N2O7P (M+H)+ calcd:
333.0852, found: 333.0844. 1H NMR—see Tables 4 and 5.
phenylsilyl-20-deoxy-50-O-isopropoxycarbonylcytidin-50-
C-ylphosphonate (26). Triphenylphosphine (908 mg,
3.46 mmol), diethyl-azodicarboxylate (0.9 ml, 4.2 mmol),
and diphenylphosphoryl azide (0.81 ml, 4.2 mmol) were se-
quentially added to a solution of hydroxyphosphonate 13 (R/
ꢁ
S 14/86) (1.17 g, 1.73 mmol) in THF (12 ml) at 0 C. After
30 min (TLC in C-1), the reaction was stopped by addition
of abs methanol (1 ml) and the solution was evaporated.
Chromatography of the residue on silica gel (elution with
a linear gradient of 0–10% ethanol in chloroform) afforded
compound 26. Yield, 453 mg (67%; yellowish foam) of 26
(R/S 80/20). For C38H45N3O10PSi (MꢀH)ꢀ calcd:
762.2612, found: 762.2618. nmax(CHCl3) 3405 (w, NH2),
3073 (m, Ph), 3055 (w, Ph), 2495 (vw, br, P–OH), 1377
(m, CH3), 1744 (s, C]O, 1698 (s, C]O, 1651 (s, sh),
1642 (s), 1624 (s, sh), 1567 (s), 1487 (vs), 1392 (s), 1363
4.1.16. Dimethyl-30-O-tert-butyldiphenylsilyl-20-deoxy-
50-O-isopropoxycarbonylthymidin-50-C-ylphosphonate
(25). Triphenylphosphine (525 mg, 2 mmol), diethyl-azodi-
carboxylate (0.52 ml, 2.4 mmol), and diphenylphosphoryl
azide (0.47 ml, 2.4 mmol) were sequentially added to a solu-
tion of hydroxyphosphonate 12b (R/S 18/82) (589 mg,
ꢁ
1 mmol) in THF (12 ml) at 0 C. After 30 min (TLC in
C-1), the reaction was stopped by addition of abs methanol
Table 6. 1H chemical shifts in compounds 25–41
Compound
Solvent
H-10
H-20
H-200
H-30
H-40
H-50
Nucleobase
(S)-25a–c
(R)-25a–c
(S)-26a–d
(R)-26a–d
(S)-27a–d
(S)-33a,e,f
(R)-33a,e,f
(S)-35a,f,g
(R)-35a,f,g
(S)-36ah
(R)-36bi
(S)-38
(R)-38
(S)-39
(R)-39
(S)-40
(R)-40
(S)-41
(R)-41
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
D2O
D2O
D2O
D2O
D2O
D2O
D2O
D2O
D2O
6.35
6.38
6.18
6.24
6.39
6.26
6.30
6.27
6.31
6.27
6.31
6.24
6.28
6.20
6.25
6.20
6.23
6.43
6.44
1.99
n
2.16
n
4.44
4.48
4.54
4.70
4.72
4.83
4.79
4.74
4.80
4.71
4.81
4.56
4.56
4.49
4.69
4.70
4.92
4.73
4.94
4.25
4.03
4.50
n
4.88
4.29
4.73
4.32
5.05
4.32
4.49
T: 11.35 (NH), 7.95 (H-6), 1.72 (5-Me)
T: 11.39 (NH), 7.68 (H-6), 1.76 (5-Me)
CBz: 11.25 (NH), 8.72 and 7.29 (H-5, H-6)
CBz: 11.25 (NH), 8.88 and 7.30 (H-5, H-6)
ABz: 8.47 (H-2, H-8)
T: 11.24 (NH), 8.14 (H-6), 1.70 (5-Me)
T: 11.26 (NH), 8.02 (H-6), 1.68 (5-Me)
T: 11.25 (NH), 7.85 (H-6), 1.68 (5-Me)
T: 11.25 (NH), 7.83 (H-6), 1.65 (5-Me)
T: 7.72 (H-6), 1.92 (5-Me)
T: 7.83 (H-6), 1.90 (5-Me)
T: 7.78 (H-6), 1.91 (5-Me)
T: 7.68 (H-6), 1.88 (5-Me)
C: 7.98 and 6.06 (H-5, H-6)
C: 8.06 and 6.05 (H-5, H-6)
G: 7.92
1.67
2.00
2.60
1.97
1.82
1.89
1.50
2.48
2.40
2.41
2.44
2.47
2.44
2.72
2.75
2.82
2.83
2.35
2.30
2.35
1.92
1.53
1.96
1.80
2.36
2.33
4.32
4.36
4.47
3.30–3.90
4.30–3.90
4.26
4.27
4.13
4.20
4.14
4.27
4.25
4.36
4.37
4.45
3.80
3.99
3.88
4.23
3.84
4.05
3.89
4.00
3.97
4.05
2.33
2.34
2.35
2.49
2.53
2.54
2.56
G: 8.02
A: 8.32, 8.19 (H-2, H-8)
A: 8.34, 8.21 (H-2, H-8)
D2O
n¼Chemical shift value was not determined.
a
30-OTBDPS: 7.64 (m, 4H) and 7.55–7.43 (m, 6H) (2ꢂC6H5), 1.07 (s, 9H, t-Bu).
P(OMe)2: 3.32–3.67 (2ꢂd, 2ꢂ3H).
b
c
d
e
f
50-O–CO–O–iPr: 4.72 (m, 1H, CH), 1.21 and 1.14 (2ꢂs, 2ꢂCH3).
Bz: 8.02 (m, 2H, o-ArH), 7.70 (m, 1H, p-ArH), 7.56 (m, 2H, m-ArH).
P(OMe): 3.22–3.30 (d, 3H, J(CH3,P)w10.5 Hz).
50-SO2CH3: 2.17–2.54 (s, 3H, CH3).
g
h
BOM: 5.34, 4.59 (2ꢂm, O–CH2–CH2–O), 8.02 (m, 2H, o-ArH), 7.70 (m, 1H, p-ArH) and 7.56 (m, 2H, m-ArH) (C6H5).
P–O–CH2–CH2–O: 4.43 (m, 1H, J(Ha,Hb)¼12.2 Hz, J(Ha,Hc)¼2.6 Hz, J(Ha,Hd)¼11.2 Hz, J(Ha,P)¼2.8 Hz, Ha); 4.18 (m, 1H, J(Hb,Ha)¼12.2 Hz,
J(Hb,Hc)¼1.2 Hz, J(Hb,Hd)¼2.6 Hz, J(Hb,P)¼17.3 Hz, Hb); 3.96 (m, 1H, J(Hc,Ha)¼2.6 Hz, J(Hc,Hb)¼1.2 Hz, J(Hc,Hd)¼12.6 Hz, J(Hc,P)¼1.2 Hz,
Hc); 3.77 (m, 1H, J(Hd,Ha)¼11.2 Hz, J(Hd,Hb)¼2.6 Hz, J(Hd,Hc)¼12.6 Hz, Hd).
i
P–O–CH2–CH2–O: 4.44 (1H, m, J(Ha,Hb)¼2.3 Hz, J(Ha,Hc)¼2.4 Hz, J(Ha,Hd)¼11.5 Hz, J(Ha,P)¼2.4 Hz, Ha); 4.17 (1H, m, J(Hb,Ha)¼12.3 Hz,
J(Hb,Hc)¼0.8 Hz, J(Hb,Hd)¼2.5 Hz, J(Hb,P)¼17.8 Hz, Hb); 3.98 (1H, m, J(Hc,Ha)¼2.4 Hz, J(Hc,Hb)¼0.8 Hz, J(Hc,Hd)¼12.7 Hz, Hc); 3.80 (1H, m,
J(Hd,Ha)¼11.5 Hz, J(Hd,Hb)¼2.5 Hz, J(Hd,Hc)¼12.7 Hz, Hd).

ˇ
S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4927
Table 7. Coupling constants in compounds 25–41
Compound
Solvent
10,20
10,200
20,200
20,30
200,30
30,40
40,50
40,P
50,P
(S)-25a–c
(R)-25a–c
(S)-26b–d
(R)-26b–d
(S)-27b,c
(S)-33a,c
(R)-33a,c
(S)-35a
(R)-35a
(S)-36aa
(R)-36ba
(S)-38a
(R)-38a
(S)-39
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
D2O
D2O
D2O
D2O
D2O
D2O
D2O
D2O
D2O
8.3
9.0
7.6
9.0
7.2
9.3
8.8
8.7
8.8
6.2
6.3
6.6
6.4
6.3
5.6
6.3
6.3
6.3
6.6
5.9
5.4
5.6
5.0
7.2
5.7
6.0
5.6
5.9
7.9
7.6
6.6
6.4
5.9
6.6
6.8
6.8
6.6
6.6
13.7
n
13.7
13.4
n
5.1
4.9
5.0
5.0
5.0
4.8
4.8
5.1
5.0
2.5
3.2
6.0
n
6.1
6.0
6.6
6.5
6.3
5.9
2.7
1.0
1.0
1.0
2.5
1.0
1.5
2.0
1.0
5.9
6.0
6.0
n
6.1
6.0
5.4
5.6
3.9
3.4
2.4
1.0
n
4.4
7.6
2.8
6.0
5.6
3.4
2.0
n
2.7
7.6
n
11.7
12.2
12.2
10.8
11.1
10.0
11.3
n
n
n
3.5
1.0
2.0
n
3.5
8.8
8.3
n
13.2
12.9
13.4
13.2
14.3
14.1
n
14.2
13.9
13.8
13.7
13.7
14.4
13.8
n
n
n
n
4.7
5.3
2.3
2.4
5.1
n
5.8
1.0
4.6
4.2
4.7
3.0
8.6
4.1
5.6
1.0
5.8
1.0
4.6
1.7
3.7
2.2
4.5
4.3
3.4
4.6
4.0
5.1
2.9
1.7
3.0
2.0
11.7
13.9
11.2
12.7
12.0
13.4
12.7
13.7
(R)-39
(S)-40
(R)-40
(S)-41
(R)-41
D2O
n¼Unresolved multiplet, J could not be determined.
a
J(6,CH3)¼1.0–1.3 Hz.
b
J(P,OCH3)¼10.5 Hz.
c
J(CH,CH3)¼6.3 Hz.
d
J(5,6)¼7.6 Hz.
(m, t-Bu), 1261 (vs), 1185 (s), 1083 (s), 1061 (s), 704 (s,
Si–O) cmꢀ1. 1H NMR—see Tables 6 and 7.
J(C,P) 3.0 Hz, 3ꢂp-C, 3ꢂPh), 131.81 (d, J(C,P) 10.3 Hz,
6ꢂm-C, 3ꢂPh), 131.0 (3ꢂi-C, 3ꢂPh), 128.49 (d, J(C,P)
12.2 Hz, 6ꢂo-C, 3ꢂPh), 101.91 (C-5), 97.97 (pCo), 86.88
(C-10), 76.22 (C-40), 68.19 (C-30), 60.28 (C-50), 40.91 (C-
20), 28.72 (CH3), 18.25 (CH3), 12.92 (5-CH3).
4.1.18. Dimethyl-6-N-benzoyl-30-O-tert-butyldiphenyl-
silyl-20-deoxy-50-O-isopropoxycarbonyladenosin-50-C-yl-
phosphonate (27). Derivative 27 was prepared from
hydroxyphosphonate 15a (R/S 24/76) (774 mg, 1.1 mmol)
according to the procedure described for compound 25.
Yield, 340 mg (40%; yellowish foam) of 27 (R/S 84/16).
For C39H45N5O9PSi (MꢀH)ꢀ calcd: 786.2725, found:
786.2723. nmax(CHCl3) 3413 (vw, NH2), 3072 (w, Ph), 3059
(w, Ph), 3030 (w, Ph), 1750 (m, C]O), 1645 (m, NH), 1612
(m, base), 1582 (m, base), 1591 (m, sh, Ph), 1561 (w, sh,
Ph), 1489 (w, Ph), 1428 (m, Ph), 1390 (m, sh, t-Bu), 1363
(m, t-Bu),1258 (vs, P]O), 1063 (s, COPOC), 1041 (s, CO-
POC), 703 (s, Si–O) cmꢀ1. 1H NMR—see Tables 6 and 7.
4.1.20. Methyl-30-O-tert-butyldiphenylsilyl-20-deoxy-50-
O-methansulfonylthymidin-50-C-ylphosphonate (33).
Phosphonate 12b (425 mg, 0.72 mmol) dried by co-distilla-
tion with pyridine (2ꢂ15 ml) was treated with mesyl chlo-
ꢁ
ride (0.28 ml, 3.6 mmol) in pyridine (7 ml) at 0 C until
the starting compound disappeared (TLC in C-1 and H-1).
The reaction was quenched by addition of water (1 ml).
Chloroform (50 ml) was added, the organic layer was
washed by saturated solution of sodium hydrogencarbonate,
dried over anhydrous Na2SO4 and evaporated. The residue
ꢁ
was treated with 60% aqueous pyridine (20 ml) at 50 C
4.1.19. [1-(2-Deoxy-3,5-O-isopropyliden-b-D-threo-pen-
tofuranosyl)-5-methylpyrimid-2-on-4-yl] iminotriphe-
nylphosphorane (32). Phosphorane 32 was prepared from
30,50-O-isopropylidene derivative 3035 (140 mg, 0.5 mmol)
according to the procedure described for compound 25.
Yield, 73 mg (27%; yellowish solid) of the derivative 32.
For C31H33N3O4P (M+H)+ calcd: 542.2208, found:
542.2203. nmax(CHCl3) 3102 (w, ]C–H), 3080 (w, ]C–
H), 3062 (w, ]C–H), 1738 (s, C]O), 1729 (s, C]O),
1708 (m, sh, C]O), 1632 (m, base), 1592 (w, base), 1562
(m, base), 1484 (w, base), 1438 (s, CH3), 1083 (s), 1120
for 16 h (TLC in C1 and H1). After complete demethylation
the solution was concentrated in vacuo, the residue was co-
distilled with ethanol and treated with Dowex 50ꢂ2 (Et3N+)
in 75% aqueous ethanol to remove N-methylpyridinium
cations. Product 33 was purified on silica gel column
using elution with a linear gradient of H-3 in ethyl acetate
and followed by a linear gradient of H-1 in H-3. Yield,
433 mg (79%; yellowish foam) of triethylammonium salt
of the derivative 33. For C28H37N2NaO10PSSi (M+Na)+
1
calcd: 675.1574, found: 675.1572. H NMR—see Tables 6
and 7.
(vs), 1162 (s), 1175 (s), 1195 (s) cmꢀ1 1H NMR, dH
.
(500 MHz, CDCl3) 8.20 (1H, q, J 1.3 Hz, H-6); 7.65–7.48
(15H, m, 3ꢂPh), 6.32 (1H, dd, J 1.2, 7.6 Hz, H-10), 4.55
(1H, bdd, J 4.5, 2.6, <1 Hz, H-30), 4.30 (1H, dd, J 13.8,
1.3 Hz, H-50a), 4.26 (1H, dd, J 13.8, 2.1 Hz, H-50b), 4.01
(1H, m, J 2.6, 2.1, 1.3 Hz, H-40), 2.75 (1H, ddd, J 15.3,
7.6, 4.5 Hz, H-200), 2.46 (3H, d, J 1.3 Hz, 5-CH3), 2.36
(1H, bdd, J 15.3, 1.2, <1 Hz, H-20), 1.51 (3H, br s, CH3),
1.35 (3H, br s, CH3); dC (125.7 MHz, CDCl3+CD3OD 9/1)
151.84 (C-2), 142.33 (C-4), 132.43 (C-6), 131.12 (d,
4.1.21. (2-Hydroxyethyl)-30-O-tert-butyldiphenylsilyl-20-
deoxy-50-O-methansulfonylthymidin-50-C-ylphosphonate
(35). A mixture of the derivative 33 (433 mg, 0.57 mmol), 2-
O-benzoyloxyethanol (246 mg, 1.48 mmol), and 4-methoxy-
pyridine-N-oxide (MPNO) (1.32 g, 10.53 mmol) dried by
co-distillation with toluene and dichloromethane was treated
with MSNT (1.01 g, 3.42 mmol) in dichloromethane (7 ml)
(TLC in C-1 and H-1). The reaction was quenched by addi-
tion of a saturated solution of sodium hydrogencarbonate.

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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4928
Chloroform (50 ml) was added, organic layer was washed
with saturated solution of sodium hydrogencarbonate, dried
over anhydrous Na2SO4, and evaporated. Mixed diester ꢁ34
was heated with 60% aqueous pyridine (20 ml) at 50 C
for 16 h (TLC in C1 and H1). The solution was concentrated
in vacuo, and the residue was co-distilled with ethanol and
treated with Dowex 50ꢂ2 (Et3N+) in 75% aqueous ethanol
to remove N-methylpyridinium cations. Product 35 was puri-
fied on silica gel column using elution with a linear gradient
of H3 in ethyl acetate and followed by a linear gradient of H1
in H3. Yield, 493 mg (97%; yellowish foam) of 35 (Et3NH+
salt). For C36H43N2NaO12PSSi (M+Na)+ calcd: 809.1941,
found: 809.1935. 1H NMR—see Tables 6 and 7.
4.1.26. 20-Deoxyadenosin-50-C-ylphosphonic acid (41).
Phosphonic acid 41 was prepared from phosphonate 15b
(R/S 22/78) (234 mg, 0.33 mmol) by consecutive application
of Methods C, D and G. Yield, 89 mg (81%) of 41 (Na+ salt;
white lyophilizate) (R/S 17/83). For C10H13N5O6P (MꢀH)ꢀ
calcd: 330.0604, found: 330.0602. nmax(KBr) 3424 (s, vbr,
NH2 or OH), 3262 (v, br, NH2 or OH), 3108 (s, br, NH2 or
OH), 3155 (m, br, sh NH or OH), 2675 (w, br, sh, NH2 or
OH), 1603 (m, sh, ring), 1581 (w, base), 1507 (w, sh,
base), 1478 (m, base), 1429 (w, base), 1334 (w, base),
1306 (w, base), 1193 (C–OH), 1083 (vs, C–OH), 997 (m,
POꢀ3 2), 907 (w, POꢀ3 2), 796 (w, base), 739 (w, br, base),
641 (w, base) cmꢀ1. 1H NMR—see Tables 6 and 7.
4.1.27. Diethyl-20,30-O-isopropylidene-3-N-methoxy-
methyluridine-50-C-ylphosphonate (48). Phosphonate 48
was obtained from diethyl phosphite (0.258 ml, 2 mmol)
and the aldehyde prepared from 20,30-O-isopropyliden-3-N-
methoxymethyluridine36 (328 mg, 1 mmol) according to
Method B. Yield, 144 mg (31%; yellowish foam) of 48 (R/
S 30/70). For C18H29N2O10P (464.40) calcd: 46.55% C,
6.29% H, 6.03% N; found: 46.31% C, 6.35% H, 5.90% N.
MS (FAB): 465.1 (M+H)+. 1H NMR—see Tables 8 and 9.
4.1.22. (5S)-[P/200-O-cyclo]-20-Deoxy-50-O-(200-hydroxy-
ethyl)thymidin-50-C-ylphosphonate (36a) and (5R)-
[P/200-O-cyclo]-20-deoxy-50-O-(200-hydroxyethyl)thymi-
din-50-C-ylphosphonate (36b). The solution of monoester
35 (493 mg,ꢁ 0.55 mmol) in 1 M sodium methoxide was
heated at 55 C for 4 d (checked by RP-HPLC). The reaction
mixture was treated with Dowex 50 (Et3NH+) and products
were purified on RP-HPLC. Yield, 15 mg (8%; white solid)
of (S)-epimer 36a and 17 mg (9%; white solid) of (R)-epimer
36b. For C12H17N2NaO8P (M+Na)+ calcd: 371.0620, found:
4.1.28. Diethyl-4-N-benzoyl-20,30-O-isopropylidenecyti-
dine-50-C-ylphosphonate (50). Phosphonate 50 was ob-
tained from diethyl phosphite (0.258 ml, 2 mmol) and the
aldehyde prepared from 4-N-benzoyl-20,30-O-isopropylid-
enecytidine37 (390 mg, 1 mmol) according to Method B.
Yield, 298 mg (57%; yellowish foam) of 50 (R/S 43/57).
For C23H30N3O9P (523.48) calcd: 52.77% C, 5.78% H,
8.03% N; found: 52.44% C, 5.72% H, 7.89% N. MS
(FAB): 524.1 (M+H)+. 1H NMR—see Tables 8 and 9.
1
371.0618 for 36a and 371.0629 for 36b. H NMR—see
Tables 6 and 7. 13C NMR—see Table 10.
4.1.23. 20-Deoxythymidin-50-C-ylphosphonic acid (38).
Phosphonic acid 38 was prepared from phosphonate 12c
(R/S 19/81) (1.161 g, 1.88 mmol) by consecutive application
of Methods C, E and G. Yield, 454 mg (75%) of 38 (Na+ salt;
white lyophilizate) (R/S 18/82). For C10H14N2O8P (MꢀH)ꢀ
calcd: 321.0488, found: 321.0494. nmax(KBr) 3417 (m, vbr,
NH2), 3270 (m, vbr, sh, OH), 3067 (m, ]C–H), 2818 (m,
br), 1696 (vs, br, C]O), 1479 (m, base), 1448 (w, base),
1410 (w, sh, base), 1388 (w, sh, base), 1372 (w, base),
1278 (m, base), 1077 (s, br, C–OH), 1055 (s, br, C–OH),
4.1.29. Dimethyl-2-N-benzoyl-20,30-O-isopropylidene-
guanosin-50-C-ylphosphonate (51). Phosphonate 51 was
obtained from dimethyl phosphite (0.183 ml, 2 mmol) and
the aldehyde prepared from 2-N-benzoyl-20,30-O-isopropyli-
deneguanosine38 (427 mg, 1 mmol) according to Method B.
Yield, 353 mg (66%; white foam) of 51 (R/S 40/60). For
C22H27N5O9P (M+H)+ calcd: 536.1546, found: 536.1554.
1H NMR—see Tables 8 and 9.
1
962 (m, POꢀ3 2), 902 (m, br, POꢀ3 2) cmꢀ1. H NMR—see
Tables 6 and 7.
4.1.24. 20-Deoxycytidin-50-C-ylphosphonic acid (39).
Phosphonic acid 39 was prepared from phosphonate 13 (R/
S 15/85) (162 mg, 0.24 mmol) by consecutive application
of Methods C, D, E and G. Yield, 55 mg (75%) of 39 (Na+
salt; white lyophilizate) (R/S 15/85). For C9H13N3O7P
(MꢀH)ꢀ calcd: 306.0491, found: 306.0498. nmax(KBr)
3429 (vs, vbr, NH2 or OH), 3200 (m, br, sh, NH2 or OH),
1646 (s, C]O), 1612 (m, sh, base), 1530 (w, base), 1494
(m, base), 1294 (w, C–NH2), 1249 (w, base), 1086 (m, C–
OH), 1048 (m, sh, C–OH), 968 (w, POꢀ3 2), 897 (m, br,
POꢀ3 2) cmꢀ1. 1H NMR—see Tables 6 and 7.
4.1.30. Diethyl-6-N-benzoyl-20,30-O-isopropylideneade-
nosin-50-C-ylphosphonate (52). Phosphonate 52 was ob-
tained from diethyl phosphite (0.258 ml, 2 mmol) and the
aldehyde prepared from 6-N-benzoyl-20,30-O-isopropylid-
eneadenosine39 (411 mg, 1 mmol) according to Method B.
Yield, 175 mg (32%; white foam) of 52 (R/S 33/67). For
C24H30N5O8P (547.50) calcd: 52.65% C, 5.52% H,
12.79% N; found: 52.34% C, 5.57% H, 12.86% N. MS
(FAB): 548.5 (M+H)+. 1H NMR—see Tables 8 and 9.
4.1.25. 20-Deoxyguanosin-50-C-ylphosphonic acid (40).
Phosphonic acid 40 was prepared from phosphonate 14b
(R/S 24/76) (1.56 g, 2.17 mmol) by consecutive application
of Methods C, D, E and G. Yield, 158 mg (21%) of 40 (Na+
salt; white lyophilizate) (R/S 29/71). For C10H13N5O7P
(MꢀH)ꢀ calcd: 346.0553, found: 346.0553. nmax(KBr) 3417
(s, br, NH2 or OH), 3120 (m, br, NH2 or OH), 2765 (m, br,
NH2 or OH), 1694 (vs, C]O), 1607 (m, base), 1580 (w,
sh, base), 1535 (w, base), 1483 (w, base), 1410 (w, base),
1179 (w, base), 1074 (m, vbr, C–OH), 968 (w, POꢀ3 2), 899
(w, br, POꢀ3 2) cmꢀ1. 1H NMR—see Tables 6 and 7.
4.1.31. Dimethyl-6-N-benzoyl-20,30-O-isopropylideneade-
nosin-50-C-ylphosphonate (53). Phosphonate 53 was ob-
tained from dimethyl phosphite (0.183 ml, 2 mmol) and
aldehyde prepared from 6-N-benzoyl-20,30-O-isopropylid-
eneadenosine39 (411 mg, 1 mmol) according to Method B.
Yield 218 mg (42%; white foam) of 53 (R/S 17/83). For
C22H27N5O8P (M+H)+ calcd: 520.0597, found: 520.0594.
1H NMR—see Tables 8 and 9.
4.1.32. 3-N-Methoxymethyluridin-50-C-ylphosphonic acid
(54). Phosphonic acid 54 was prepared from phosphonate

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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4929
Table 8. 1H chemical shifts in compounds 48–62
Compound
Solvent
H-10
H-20
H-30
H-40
H-50
50-OH
Nucleobase
(S)-48a–c
(R)-48a–c
(S)-50b–d
(R)-50b–d
(S)-51b,d,e
(R)-51b,d,e
(S)-52b–d
(R)-52b–d
(S)-53b,d,e
(R)-53b,d,e
(S)-54a
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
D2O
D2O
D2O
D2O
D2O
D2O
D2O
D2O
D2O
5.87
5.92
5.88
5.91
6.13
6.16
6.29
6.31
6.29
6.31
5.98
5.92
5.91
5.87
5.89
5.84
5.87
5.83
6.06
6.08
5.90
5.91
6.09
6.39
4.97
4.84
4.97
4.85
5.39
5.23
5.46
5.29
5.46
5.29
4.41
4.40
4.39
4.39
4.32
4.34
4.73
4.68
4.75
4.74
4.90
4.88
5.37
5.32
4.99
4.87
5.02
4.89
5.27
5.16
5.23
5.08
5.23
5.08
4.50
4.33
4.45
4.24
4.39
4.15
4.71
5.15
4.71
4.46
4.96
5.20
5.73
5.82
4.22
4.33
4.33
4.43
4.30
4.40
4.41
4.53
4.41
4.43
4.47
4.35
4.45
4.29
4.47
4.26
4.53
5.13
4.59
4.41
4.43
4.53
4.72
4.74
4.07
4.15
4.21
4.18
3.98
4.26
4.03
4.22
4.03
4.22
4.14
3.99
4.10
3.87
4.12
3.83
4.04
3.94
4.06
3.90
3.99
4.16
5.57
5.52
6.23
6.39
6.20
6.22
6.30
6.29
n
n
n
n
—
—
—
—
—
—
—
—
—
—
5.85
6.10
n
UMeM: 7.84 (H-6), 5.78 (H-5)
UMeM: 8.07 (H-6), 5.79 (H-5)
CBz: 11.32 (NH), 8.28 (H-6), 7.35 (H-5)
CBz: 11.30 (NH), 8.59 (H-6), 7.33 (H-5)
GBz: 11.32 (NH), 8.24 (H-8)
GBz: 11.33 (NH), 8.36 (H-8)
ABz: 11.23 (NH), 8.77, 8.65 (H-2, H-8)
ABz: 11.22 (NH), 8.82, 8.76 (H-2, H-6)
ABz: 11.23 (NH), 8.77, 8.65 (H-2, H-8)
ABz: 11.23 (NH), 8.81, 8.75 (H-2, H-8)
UMeM: 8.13 (H-6), 6.00 (H-5)
UMeM: 8.11 (H-6), 5.98 (H-5)
U: 8.15 (H-6)
(R)-54a
(S)-55
(R)-55
(S)-56
(R)-56
(S)-57
(R)-57
(S)-58
U: 7.98 (H-6)
C: 8.16 (H-6), 6.04 (H-5)
C: 7.89 (H-6), 6.04 (H-5)
G: 8.02 (H-8)
G: 7.91 (H-8)
A: 8.42, 8.21 (H-2, H-8)
A: 8.32, 8.19 (H-2, H-8)
—
—
—
(R)-58
D2O
(S)-60b,c,f
(R)-60b,c,f
(R)-62(b)c,f,g
(R)-62(a)c,f,g
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
n
—
n¼Not detected.
a
MeM: 5.16–5.37 (s or 2ꢂd, 2H, N–CH2), 3.26–3.44 (s, 3H, OCH3).
–O–C(CH3)2–O–: 1.29–1.58 (2ꢂs, 2ꢂ3H).
b
c
d
e
f
P(OEt)2: 3.95–4.10 (2ꢂm, 2ꢂ2H, 2ꢂCH2), 1.04–1.25 (2ꢂt, 2ꢂ3H, 2ꢂCH3).
NBz: 7.87–8.05 (m, 2H), 7.52–7.70 (m, 1H), 7.44–7.56 (m, 2H).
P(OMe)2: 3.60–3.62 and 3.51–3.52 (2ꢂd, 2ꢂ3H).
30-OBz: 8.02 (m, 2H), 7.70 (m, 1H), 7.56 (m, 2H).
10,20,30-triOAc: 1.85–2.17 (3ꢂs, 3ꢂ3H).
g
48 (R/S 30/70) (600 mg, 1.29 mmol) by consecutive applica-
tion of Methods C, F and G. Yield, 461 mg (97%) of 54 (Na+
salt; white lyophilizate) (R/S 45/55). For C11H16N2O10P
(MꢀH)ꢀ calcd: 367.0543, found: 367.0541. nmax(KBr)
3417 (s, NH2 or OH), 3272 (s, vbr, sh, NH2 or OH), 3108
(m, NH2 or OH), 2970 (m, CH3), 2836 (m, CH3), 1714 (s,
C]O), 1660 (vs, br, C]O), 1629 (s, sh, base), 1463 (s,
base), 1414 (m, base), 1115 (s, COC), 1083 (s, C–OH),
1
1056 (s, sh, C–OH), 972 POꢀ3 2), 912 (m, PO3ꢀ2) cmꢀ1. H
NMR—see Tables 8 and 9.
Table 9. Coupling constants in compounds 48–62
Compound
Solvent
10,20
20,30
30,40
40,50
40,P
50,P
50,OH
P,OH
(S)-48a–c
(R)-48a–c
(S)-50a–c
(R)-50a–c
(S)-51d
(R)-51d
(S)-52b
(R)-52b
(S)-53d
(R)-53d
(S)-54a
(R)-54a
(S)-55a
(R)-55a
(S)-56a
(R)-56a
(S)-57
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
D2O
D2O
D2O
D2O
D2O
D2O
D2O
D2O
D2O
2.2
2.7
2.2
2.2
2.7
2.7
2.9
2.9
2.9
2.9
4.6
3.4
3.5
3.3
2.7
2.4
5.0
5.5
4.6
4.6
3.8
3.9
1.0
4.2
6.6
6.4
6.4
6.1
6.2
6.2
6.1
6.1
6.1
6.1
4.9
5.1
n
5.3
5.1
5.4
5.5
5.3
5.1
4.9
5.1
5.6
5.0
6.5
2.2
2.9
2.4
2.9
2.2
2.2
2.2
2.2
2.0
2.2
4.9
6.1
n
6.6
7.1
7.1
3.4
4.3
4.6
4.9
8.5
7.6
6.6
2.7
5.6
3.9
5.1
3.4
5.7
3.8
4.9
3.2
5.0
3.4
1.7
3.4
1.5
5.4
1.7
7.1
2.0
3.6
1.5
5.0
2.7
2.4
3.4
2.6
5.1
0.5
4.9
2.7
4.5
3.4
4.4
2.8
4.2
3.1
1.7
6.3
n
2.9
1.7
2.9
1.2
2.6
1.5
2.4
2.7
3.9
2.6
2.6
8.8
11.5
8.8
10.8
8.4
11.1
9.8
12.0
9.3
12.0
13.2
12.9
13.0
11.9
12.9
11.2
13.9
12.7
13.9
12.0
13.0
13.0
13.1
12.6
6.8
7.0
6.4
8.0
6.7
6.9
6.8
7.3
6.6
6.3
—
—
—
—
—
—
—
—
—
6.6
8.8
6.4
8.0
5.7
8.9
7.1
6.5
7.3
7.3
—
—
—
—
—
—
—
—
—
(R)-57
(S)-58
(R)-58
D2O
—
—
(S)-60b
(R)-60b
(R)-62(b)b
(R)-62(a)b
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
8.0
6.6
—
8.4
12.8
—
—
—
a
J(5,6)¼7.3–8.3 Hz.
J(CH2,CH3)¼7.1 Hz.
J(P,OCH2)¼7.3 Hz.
J(P,OCH3)¼10.5 Hz.
b
c
d

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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4930
4.1.33. Uridin-50-C-ylphosphonic acid (55). Diester 49 was
obtained from diethyl phosphite (0.516 ml, 4 mmol) and the
aldehyde prepared from 20,30-O-isopropylideneuridine40
(568 mg, 2 mmol) according to Method B. This derivative
was transformed into free phosphonic acid 55 by consecu-
tive application of Methods C, F and G. Yield, 298 mg
(46%) of 55 (Na+ salt; white lyophilizate) (R/S 45/55). For
C9H12N2O9P (MꢀH)ꢀ calcd: 323.0280, found: 323.0290.
nmax(KBr) 3418 (s, vbr, NH2 or OH), 3248 (s, vbr, sh, NH2
or OH), 2806 (m, vbr, NH2 or OH), 1782 (m, sh, base),
1699 (vs, vbr, C]O), 1628 (s, sh, base), 1470 (m, base),
1441 (m, base), 1398 (m, base), 1274 (m, base), 1105 (s,
br, OH), 1058 (s, br, C–OH), 969 (m, POꢀ3 2), 921 (w,
base), 1089 (m, C–OH), 1043 (m, C–OH), 971 (w, POꢀ3 2),
899 (w, br, POꢀ3 2) cmꢀ1. 1H NMR—see Tables 8 and 9.
4.1.35. Guanosin-50-C-ylphosphonic acid (57). Phos-
phonic acid 57 was prepared from phosphonate 51 (R/S 40/
60) (700 mg, 1.3 mmol) by consecutive application of
Methods C, D, F and G. Yield 378 mg (80%) of 57 (Na+
salt; white lyophilizate) (R/S 44/56). For C10H13N5O8P
(MꢀH)ꢀ calcd: 362.0503, found: 362.0504. nmax(KBr)
3417 (m, vbr, NH2 or OH), 3119 (m, vbr, NH2 or OH), 2766
(w, br, NH2 or OH)), 1698 (vs, C]O), 1550 (m, base),
1582 (w, sh, base), 1536 (w, base), 1485 (w, base), 1412 (w,
base), 1102 (w, base), 1180 (w, base), 1070 (m, vbr, C–
OH), 972 (w, PO3ꢀ2) cmꢀ1. 1H NMR—see Tables 8 and 9.
1
POꢀ3 2) cmꢀ1. H NMR—see Tables 8 and 9. 13C NMR—
see Table 10.
4.1.36. Adenosin-50-C-ylphosphonic acid (58). Phosphonic
acid 58 was prepared from phosphonate 52 (R/S 33/67)
(175 mg, 0.32 mmol) by consecutive application of Methods
C, D, F and G. Yield, 85 mg (77%) of 58 (Na+ salt; white lyo-
philizate) (R/S 40/60). For C10H13N5O7P (MꢀH)ꢀ calcd:
346.0553, found: 346.0553. nmax(KBr) 3419 (vs, br, NH2
or OH), 3265 (s, br, sh, NH2 or OH), 3217 (s, br, NH2 or
OH), 3120 (m, br, sh, NH2 or OH), 2675 (w, br, sh, NH2 or
OH), 1606 (m, sh, base), 1579 (w, base), 1505 (w, sh,
base), 1476 (m, base), 1419 (w, base), 1334 (w, base),
4.1.34. Cytidin-50-C-ylphosphonic acid (56). Phosphonic
acid 56 was prepared from phosphonate 50 (R/S 43/57)
(342 mg, 0.65 mmol) by consecutive application of Methods
C, D, F and G. Yield, 105 mg (50%) of 56 (Na+ salt; white
lyophilizate) (R/S 44/56). For C9H13N3O8P (MꢀH)ꢀ calcd:
322.0440, found: 322.0435. nmax(KBr) 3427 (vs, br, NH2 or
OH), 3206 (m, br, sh, NH2 or OH), 1652 (s, C]O), 1610
(m, base), 1521 (w, base), 1499 (m, base), 1287 (w, C–NH2),
1253 (w, base), 1211 (w, base), 1185 (w, br, base), 1120 (m,
Table 10. 13C NMR data of compounds 12e, 12f, 14a, 25, 36 and 55
Compound
Solvent
C-10
C-20
C-30 J(C,P)
C-40 J(C,P)
C-50 J(C,P)
Nucleobase
(S)-12ba
DMSO-d6
85.03
w39.7
75.51 d (15.1)
86.86
66.68 (164.3)
T: 163.86 (C-4); 150.59 (C-2); 136.34 (C-6);
109.29 (C-5); 12.41 (5-CH3)
(S)-12eb
(R)-12ec
(S)-12fd
(R)-12fe
(S)-14af
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
DMSO-d6
84.80
84.03
84.82
84.60
83.98
39.54
39.54
37.34
38.03
41.18
73.49 d (14.6)
73.07 (4.9)
76.86 d (14.6)
73.96
86.72 (w0)
86.89 (10.8)
83.97 (w0)
83.66 (10.2)
87.44 (w0)
66.69 d (165.0)
63.72 (159.2)
67.12 d (165.0)
68.13 (160.6)
66.74 (163.1)
T: 163.99 (C-4); 150.66 (C-2); 136.57 (C-6);
109.28 (C-5); 12.51 (5-CH3)
T: 163.86 (C-4); 150.75 (C-2); 136.09 (C-6);
109.86 (C-5); 12.32 (5-CH3)
T: 163.89 (C-4); 150.62 (C-2); 136.35 (C-6);
109.56 (C-5); 12.48 (5-CH3)
T: 164.13 (C-4); 150.62 (C-2); 135.96 (C-6);
111.36 (C-5); 12.17 (5-CH3)
75.74 (14.6)
GBz: 169.32, 132.53, 128.71(2), 128.73(2),
133.24 (NBz); 155.27 (C-6), 148.55 (C-4),
139.39 (C-2), 137.86 (C-8), 120.57 (C-5)
GBz: 169.35, 132.53, 128.71(2), 128.76(2),
133.35 (NBz); 155.28 (C-6), 149.06 (C-4),
139.40 (C-2), 138.22 (C-8), 120.84 (C-5)
T: 163.68 (C-4), 150.56 (C-2), 135.44 (C-6),
109.82 (C-5), 12.23 (5-CH3)
T: 169.49 (C-4), 154.50 (C-2), 140.53 (C-6),
113.92 (C-5), 14.52 (5-CH3)
T: 169.51 (C-4), 154.65 (C-2), 140.60 (C-6),
114.01 (C-5), 14.56 (5-CH3)
(R)-14ag
DMSO-d6
83.27
38.61
74.97 (8.8)
87.54 (6.8)
67.11 (160.2)
(S)-25h
(S)-36ai
(R)-36bj
(S)-55
DMSO-d6
D2O
84.28*
89.14
87.91
88.71
90.02
38.75
41.54
41.54
74.75
74.28
73.60 d (9.2)
74.38
84.25*
70.17 d (163.5)
80.38 d (140.1)
80.44 d (141.1)
69.48 d (142.6)
69.71 d (148.4)
88.38 d (5.9)
88.11 d ( 6.8)
84.94 d (12.7)
84.10 d (3.9)
D2O
73.63 d (3.4)
67.42
D2O
U: 166.36 (C-4), 151.69 (C-2), 141.87 (C-6),
101.92 (C-5)
U: 166.41 (C-4), 151.61 (C-2), 142.23 (C-6),
101.83 (C-5)
(R)-55
D2O
70.14
a
P(OCH3)2: 52.99 and 52.53 (2ꢂd, J(C,P)¼6.8 Hz); TBDPS: 135.44(4), 132.90, 132.78, 130.38, 130.35, 128.28(2) and 128.25(2) (2ꢂC6H5), 26.87(3) and
18.76 (t-Bu).
b
c
d
e
f
P(OCH3)2: 53.17 and 52.63 (2ꢂd, J(C,P)¼6.8 Hz); TBDMS: 25.86(3) and 17.83 (t-Bu), 4.65 and 4.52 (2ꢂMe).
P(OCH3)2: 53.32 and 52.62 (2ꢂd, J(C,P)¼6.8 Hz); TBDMS: 25.78(3) and 17.70 (t-Bu), 4.69 and 4.52 (2ꢂMe).
OBz: 165.48 (CO); 133.86(1), 129.60(2), 129.42 (1) and 129.00(2) (C6H5); 53.19 and 52.66 (2ꢂd, J(C,P)¼6.8 Hz, P(OCH3)2).
P(OCH3)2: 53.87 and 53.24 (2ꢂd, J(C,P)¼7.3 Hz); OBz: 165.58 (CO); 133.44(1), 129.61(2), 129.24 (1) and 128.42(2) (C6H5).
P(OCH3)2: 53.03 and 52.41 (2ꢂd, J(C,P)¼5.9 Hz); TBDPS: 135.51(2), 135.48(2), 132.90, 132.75, 130.46, 130.42, 128.34(2) and 128.32(2) (2ꢂC6H5),
26.94(3) and 18.81 (t-Bu).
g
h
P(OCH3)2: 52.88 and 52.34 (2ꢂd, J(C,P)¼6.8 Hz); TBDPS: 135.64(2), 135.56(2), 132.79, 132.25, 130.31, 130.21, 128.22(2) and 128.12(2) (2ꢂC6H5),
26.96(3) and 18.90 (t-Bu).
O–CO–OiPr: 153.08 (d, J(C,P)¼4.6 Hz, O–CO–O); 73.35, 21.40 and 21.25 (iPr); TBDPS: 135.44(4), 132.60, 132.42, 130.38, 130.36, 128.20(2) and
128.18(2) (2ꢂC6H5); 26.79(3) and 18.76 (t-Bu); P(OCH3)2: 53.58 (d, J(C,P)¼6.4) and 53.24 (d, J(C,P)¼6.0 Hz).
P–O–CH2–CH2–O: 71.81 (d, J(C,P)¼6.8 Hz); 70.15 (d, J(C,P)¼3.4 Hz).
i
j
P–O–CH2–CH2–O: 71.80 (d, J(C,P)¼6.8 Hz); 70.51 (d, J(C,P)¼2.9 Hz).
*
The assignment of signals may be interchanged.

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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4931
1297 (w, base) 1102 (vs, C–OH), 1069 (vs, C–OH), 989 (m,
POꢀ3 2), 905 (POꢀ3 2) cmꢀ1. 1H NMR—see Tables 8 and 9.
and the residue was partitioned between chloroform
(300 ml) and water (3ꢂ300 ml). The organic layer was dried
over anhydrous Na2SO4 and evaporated. The residue was
dissolved in 60%ꢁacetic acid (600 ml) and the reaction mix-
ture heated at 50 C for 3 h (TLC in T1 and C1). Acetic acid
was evaporated and the product was partitioned between
chloroform and water. The organic layer was dried over an-
hydrous Na2SO4 and evaporated. The obtained 3-O-benz-
oyl-1,2-O-isopropylidene-a-D-allofuranose was dissolved
in an acetone–water mixture (7/3, 300 ml) and the solution
of sodium periodate (12.84 g, 60 mmol) in the same solvent
4.1.37. (R)-Adenosin-50-C-ylphosphonic acid ((R)-58). 6-
N-Benzoyladenine (1.6 g, 6.7 mmol) in hexamethyldisila-
zane (67 ml, 315 mmol) was refluxed in the preꢁsence of
trimethylsilyl chloride (6.7 ml, 53.6 mmol) at 150 C under
stirring and exclusion of moisture for 10 h. Volatiles were re-
moved under reduced pressure and the resulting oil was co-
distilled with xylene (2ꢂ50 ml) and acetonitrile (2ꢂ50 ml)
to remove traces of HMDS. A solution of diethyl phospho-
nate (R)-62 (2.871 g, 5.56 mmol) (dried by co-distillation
with acetonitrile) in acetonitrile (2ꢂ20 ml) was added under
argon to the silylated base and then tin tetrachloride
(11.12 mmol, 1.31 ml) was added. The mixture was kept at
rt for 24 h (TLC in C1 and H1). The reaction mixture was
then diluted with pyridine (2 ml) and toluene (40 ml) and
stirred overnight. The thick suspension (precipitated com-
plex of tin tetrachloride with pyridine) was filtered through
Celite, washed with chloroform, and the solvents were re-
moved under diminished pressure. All protecting groups of
the product (R)-64 were removed by consecutive application
of Methods C, D and G. Yield, 669 mg (35%) of (R)-58 (Na+
salt; white lyophilizate) (R/S 100/0). For C10H13N5O7P
ꢁ
(250 ml) was added at 0 C under vigorous stirring (TLC in
T1 and C1). When the starting compound disappeared ꢁthe
mixture was diluted with acetone (200 ml), cooled to 0 C,
and filtered through Celite. After evaporation of the solvent
the crude aldehyde was co-distilled with toluene and treated
with diethyl phosphite (7.74 ml, 66 mmol) in dichlor-
methane (100 ml) in the ꢁpresence of triethylamine
(2.78 mmol, 20 mmol) at 80 C for 15 h (TLC in T1 and
C1). The reaction mixture was diluted with ethyl acetate, fil-
tered through Celite, and after evaporation of solvent the
product was isolated by chromatography on silica gel (elu-
tion with a linear gradient of 0–50% ethyl acetate in tolu-
ene). Yield, 2.54 g of product (R)-60, 3.65 g of product
(S)-60 and 11.11 g of a mixture of both products (total yield,
64%; all fractions as yellowish oil). For C19H28O9P (M+H)+
calcd: 431.1471, found: 431.1466 for (R)-60 and 431.1468
for (S)-60. 1H NMR—see Tables 8 and 9.
1
(M+H)+ calcd: 346.0553, found: 346.0550. H NMR—see
Tables 8 and 9.
4.1.38. Adenosin-50-C-ylphosphonyl morpholide ((R)-59).
The sodium salt of adenosine 50-C-phosphonate (R)-58
(10 mg, 0.029 mmol) was converted to pyridinium salt on
Dowex 50 (5 ml, Py). Morpholine (0.012 ml, 0.13 mmol)
was added to the pyridinium salt, the mixturewas evaporated,
the residue was co-distilled with ethanol (5ꢂ15 ml), dis-
solved in a mixture of tert-butanole–water (2 ml, 1/1) and
then morpholine (0.023 ml, 0.26 mmol) and DCC (40 mg,
0.19 mmol) were added to the solution. The reaction mixture
was kept under reflux for 15 h. Then volatiles were removed
under reduced pressure, the residue was suspended in water
(10 ml), filtered through Celite, and the filtrate was extracted
with ether (2ꢂ10 ml). The aqueous layer was concentrated
and the residue was co-distilled with ethanol (2ꢂ20 ml)
and suspended in 1/1 ethanol–ether mixture. Morpholide
(R)-59 was filtered and dried in vacuo. Yield, 22 mg; mixture
of (R)-59 and N-morpholino-dicyclohexylcarboxamidine
(47%, apparent molecular weight calculated from UV
spectrum (3¼14,000) was 1522). For C14H20N6O7P
(MꢀH)ꢀ calcd: 415.1216, found: 415.1210. dH (500 MHz,
DMSO-d6) 8.35 (1H, s, H-2), 8.13 (1H, s, H-8), 7.28 (2H,
br s, NH2), 5.84 (1H, d, J 3.2 Hz, H-10), 5.16 (1H, dd, J 5.2,
3.2 Hz, H-20), 4.17 (1H, dd, J 6.3, 5.2 Hz, H-30), 4.03 (1H,
ddd, J 6.8, 6.3, 3.4 Hz, H-40), 3.56 (1H, dd, J 9.8, 6.8 Hz,
H-50), 3.69 (2H, m), 3.42 (2H, m), 2.97 (2H, m), 2.93 (2H, m).
4.1.40. (5R)-Diethyl-(1,5-di-O-acetyl-3-O-benzoyl-D-
ribofuranos-5-C-yl)phosphonate ((R)-62). Sugar phospho-
nate (R)-60 (3.0 g, 6.97 mmol) dried by co-distillation with
pyridine (2ꢂ15 ml) was treated with acetic anhydride
(3.29 ml, 34.9 mmol) in pyridine (50 ml) in the presence of
DMAP (50 mg, 0.41 mmol) at rt under exclusion of moisture
until the starting compound disappeared (15 h; TLC in C1
and H1). The reaction was quenched by addition of abs meth-
anol (2 ml), the solvent was evaporated, the residue was di-
luted with ethyl acetate, and the organic layer was washed
with 10% citric acid (3ꢂ150 ml) and dried over anhydrous
Na2SO4. After evaporation of ethyl acetate, the residue (R)-
61 was co-distilled with toluene (2ꢂ20 ml) and treated
with acetic anhydride (3.0 ml, 31.8 mmol), acetic acid
(1.9 ml, 31.8 mmol) and sulfuric acid (0.3 ml, 4 mmol) in di-
ꢁ
chloromethane (20 ml) at 0 C for 48 h (TLC in C1 and H1).
Then anhydrous sodium acetate (470 mg, 5.7 mmol) was
added to neutralize sulfuric acid, and the reaction mixture
was stirred for 20 min. Tꢁhe solvents were evaporated under
oil-pump vacuum at 40 C in a bath, the residue was dis-
solved in ethyl acetate, and washed with a saturated solution
of sodium chloride. The organic layer was dried over anhy-
drous Na2SO4. Chromatography of the crude product on sil-
ica gel (elution with a linear gradient of acetone in toluene)
afforded the expected phosphonate. Yield, 2.871 g (80%;
yellowish oil) of product (R)-62 (a/b 1/4). For C22H30O12P
4.1.39. (5R)-Diethyl-(3-O-benzoyl-1,2-O-isopropylidene-
D-ribofuranos-5-C-yl)phosphonate ((R)-60) and (5S)-di-
ethyl-(3-O-benzoyl-1,2-O-isopropylidene-D-ribofuranos-
5-C-yl)phosphonate ((S)-60). Benzoyl cyanide (7.2 g,
55 mmol) followed by triethylamine (0.7 ml, 5 mmol)
were added to the solution of 1,2:5,6-di-O-isopropylidene-
a-D-allofuranose41 (13.01 g, 50 mmol, co-distilled with
1
(M+H)+ calcd: 517.1475, found: 517.1474. H NMR—see
Tables 8 and 9.
Acknowledgement
ꢁ
toluene) in acetonitrile (60 ml) at 0 C, and the reaction
Support by grants No. 203/04/P273 (GA CR), 203/05/0827
(GA CR), and A4055101 (GAAS CR) is gratefully acknowl-
edged. Authors are indebted to Professor Eric deClercq
mixture was stirred at rt for 15 h (TLC in T1). After addition
of abs methanol (2 ml) the solvent was evaporated in vacuo

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S. Krꢀal´ıkovꢀa et al. / Tetrahedron 62 (2006) 4917–4932
4932
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