New 3′-deoxythymidines bearing a nucleophilic 3′-substituent

Article abstract of DOI:10.1081/NCN-100001439

New potential cancer-driven as well as HIV-driven nucleoside heteroanalogs, such as 3′-thio- and 3′- as well as 5′-selenosubstituted thymidines, have been synthesized. We also report an effective method for the preparation of novel nucleoside derivatives, bis(deoxynucleoside) diselenides, in nearly quantitative yields. The North conformation is significantly populated in the conformational equilibrium for 3′-α-alkylthiothymidines.

Full text of DOI:10.1081/NCN-100001439

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NEW 3′-DEOXYTHYMIDINES BEARING A NUCLEOPHILIC
3′-SUBSTITUENT
Anatoly M. Belostotskii a , Helen Keren-Yeshuah a , Jael Lexner a & Alfred Hassner a
a Chemistry Department , Bar-Ilan University , Ramat-Gan, 52900, Israel
Published online: 17 Aug 2006.
To cite this article: Anatoly M. Belostotskii , Helen Keren-Yeshuah , Jael Lexner & Alfred Hassner (2001) NEW 3′-
DEOXYTHYMIDINES BEARING A NUCLEOPHILIC 3′-SUBSTITUENT, Nucleosides, Nucleotides and Nucleic Acids, 20:1-2, 93-101,
DOI: 10.1081/NCN-100001439
To link to this article: http://dx.doi.org/10.1081/NCN-100001439
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NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS, 20(1&2), 93–101 (2001)
NEW 3ꢀ-DEOXYTHYMIDINES BEARING
A NUCLEOPHILIC 3ꢀ-SUBSTITUENT
Anatoly M. Belostotskii,∗ Helen Keren-Yeshuah, Jael Lexner,
and Alfred Hassner
Chemistry Department, Bar-Ilan University, 52900 Ramat-Gan, Israel
ABSTRACT
New potential cancer-driven as well as HIV-driven nucleoside hetero-
analogs, such as 3ꢀ-thio- and 3ꢀ- as well as 5ꢀ-selenosubstituted thymidines,
have been synthesized. We also report an effective method for the preparation
of novel nucleoside derivatives, bis(deoxynucleoside) diselenides, in nearly
quantitative yields. The North conformation is significantly populated in the
conformational equilibrium for 3ꢀ-α-alkylthiothymidines.
Many 3ꢀ-modified deoxynuleosides are antiretroviral and anticancer agents of
varying potency (1). For instance, 3ꢀ-azido-3ꢀ-deoxythymidine (AZT) is still one of
the most widely used drugs in the AIDS treatment. After being triphosphorylated
in vivo, these agents essentially suppress virus reproduction or cell proliferation
via termination of the cDNA chain elongation, a polymerization reaction, which
is provided by the viral reverse transcriptase (RT) or cellular DNA-polymerases
(DNApol), respectively [see Schinazi and DeClercq (1)]. The mechanism of this
termination involves inhibition of the RT-mediated transcription of viral RNA or
DNApol-assisted replication of genomic DNA via attachment of a 3ꢀ-modified
nucleoside analog to the growing 3ꢀ-terminus of the cDNA strain [see Schinazi,
DeClercq, and Arnold and Arnold (1)].
∗Address correspondence to Anatoly M. Belostotskii.
93
ꢁ
C
Copyright 2001 by Marcel Dekker, Inc.
www.dekker.com

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BELOSTOTSKII ET AL.
Figure 1. Highly active nucleosides with nucleophilic 3ꢀ-substituent.
Among the relatively small number of known 3ꢀ-deoxynucleoside analogs
bearing a nucleophilic 3ꢀ-substituent [see Schinazi, DeClercq, Arnold and Arnold,
and DeClercq (1) as well as (2)], a significant proportion of these compounds
possesses remarkable termination activity. For instance, 3ꢀ-mercapto derivative 1a
(see Fig. 1) demonstrates the same termination activity as AZT (3). Also, the
3ꢀ-amino analog 1b effectively blocks the biosynthesis of cDNA, being attached
to the 3ꢀ-terminus by RT [see Kedar et al. (1)] or DNApol [see Chidgeavadze
et al. (2)]. Other nucleoside inhibitors of the virus and cell reproductive cycle are
hydroxylamines 1c and 1d [see Ng and Orgel (1); Schreiber and Ikemoto (4)].
Normal cDNA biosynthesis involves nucleophilic attack of the 3ꢀ-OH group
in the cDNA 3ꢀ-terminus on the 5ꢀ-triphosphate fragment of nucleotide substrates.
Thymidines 1a and 1b are incorporated by RT or DNApol into the nascent DNA
chain; however, this cDNA chain with the 3ꢀ-SH or 3ꢀ-NH2 function in the 3ꢀ-
terminus is not elongated further by the enzymes [see Kedar et al. (1); Chidgeavadze
et al. (2); Yuzhakov et al. (3)]. We consider it likely that the inhibition by thymidine
derivatives with nucleophilic 3ꢀ-substituents (SH or NH2) may be caused by binding
of bivalent metal cations [see Domenico et al. and Johannsen et al. (5)], necessary
components of the RT as well as DNApol polymerization domains [see Kati et al.
and Wohrl et al. (5)], by these electron donating 3ꢀ-substituents as complexation
ligands.
Thus, a more nucleophilic 3ꢀ-substituent (such as SeH) is desirable for inhibi-
tion of RT/DNApol-directed polymerization from the viewpoint of the complexa-
tion hypothesis. However, deoxynucleoside selenols themselves are so far unknown
and are not an attractive synthetic goal because of the extreme susceptibility of an
SeH function to oxidation. We therefore considered a prodrug approach∗ and report
herein the synthesis of new nucleosides with a nucleophilic 3ꢀ-substituent, which
include novel seleno deoxynucleosides, namely bis(deoxynucleoside) diselenides.
The latter were chosen as potential in vivo precursors of the corresponding deoxynu-
cleoside selenols. Indeed, similarly to the well-known enzymatic transformation of
the S−S function to SH groups, Se−Se compounds are also reduced in vivo to
selenols (7). Among nucleoside diselenides, only thymidine diselenide 6b has been
reported as a by-product of the hydrolysis of the corresponding 3ꢀ,5ꢀ-dithymidine
selenophosphate (8).
We developed a synthesis of the bis(deoxynucleoside) diselenides, using de-
oxynucleoside selenocyanates and easily handled borohydride reagents. A
∗ Recently we proposed deoxynucleoside selenocyanates as masked selenol deoxynucleosides.

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3ꢀ -SUBSTITUTED 3ꢀ -DEOXYTHYMIDINES
95
Scheme 1. Preparation of bis(nucleoside) diselenides.
convenient method for preparation of thymidine selenocyanates has been described
recently (6). Uridine selenocyanate 2 was obtained in 56% yield in the same manner
from the corresponding 5ꢀ-tresylate and NBu4SeCN (see Scheme 1). Hydride reduc-
tion of simple alkylselenocyanates to corresponding diselenides have been reported
[see Salama and Charles, Witczak and Czernecki, and Krief et al. (9)]. However,
conditions for minimal side-product formation [see Krief et al. (9)] (0.25 eq. of
NaBH4, EtOH, 0◦C, Ar atmosphere) led to conversion of nucleoside selenocyanates
3–5a into diselenides 6a–8a only in 25–50% yields. Deprotection of trityl derivative
6a (80% AcOH, reflux) led to the desired deoxythymidine 6b.
Since the low-yield problems could arise due to the presence of four ac-
tive hydrogen atoms inthe borohydride anion [see Krief et al., Tetrahedron (9)],
we chose NaBH(AcO)3 as a simple and successful alternative for the nucleoside
selenocyanate–diselenide transformation. Using this reagent, compounds 2, 3, 5a,
and 5b were reduced (EtOH, 25◦C, 1 h, Ar atmosphere) to diselenides 9, 6a, 8a, and
8b, respectively, in 85–100% yields. Our attempts to find a mild solvolytic route to
diselenides were less successful: treatment of selenocyanates 10 and 5a in a MeOH
solution with catalytic amount of K2CO3 led to formation of diselenides 11 and 8b,
respectively, only in 15–20% yields [see Krief et al., Angew. Chem., Int. Ed. (9) for
related reactions]. Alcohol 5b was a major product in the case of acetate 5a. The
yield of 5b was lowered when a 10-fold larger amount of the base was employed;
however, no proportional increase of the yield of 8b was observed.
In principle, reduced 6b (i.e., the 3ꢀ-SeH compound) may possess DNA elon-
gation activity despite the supposed complexation ability, if incorporated into the
cDNA chain. Therefore we turned to the synthesis of 3ꢀ-deoxythymidines possess-
ing a remote nucleophilic group at the 3ꢀ-position. These model bidentate S,X-
containing (X = OH, SH, NH2) nucleoside ligands (compounds of type 15 or 17)

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BELOSTOTSKII ET AL.
Figure 2. Preparation of 3ꢀ-S-alkyl-3ꢀ-deoxythymidines.
could be capable of metal cation chelation [see Domenico et al. and Johannsen et al.
(5)], but should possess no activity in the DNApol or RT-mediated chain elongation
due to the absence of the 3ꢀ-OH group.
Thisinvolvedmesylate-basedactivationofthe3ꢀ-β-OHgroup, inspiteofcom-
plications due to concurrent mesylate elimination expected to occur when mercap-
tan nucleophiles are employed [see Bera et al. (10)]. Thus, interaction of three-fold
excess of mercaptans 12a–f with mesylate 13b or 13c in the presence of 3 eq. of
DBU (DMF, 70◦C, 5–20 h) led to the corresponding nucleosides 15a–f and accom-
panying elimination products 16b or 16c, respectively (see Fig. 2). Deprotection
of the 5ꢀ-hydroxy group of 15a–d (reflux in 80% AcOH) led to desired substrate
analogs 17a–d.
The more reactive tresylate 13a was converted only into the intramolecu-
lar cyclization product 14 in the reaction with 12a and DBU (DMF, 25◦C, 4 h).
Relatively high yields of 3ꢀ-α-deoxythymidine sulfides have been reported for the
interaction of the corresponding 2,3ꢀ-anhydro compounds with nonfunctionalized
thiolates (iso-PrSNa [see Joshi and Reese (10)] as well as PhSH in the presence
of Pr3N [see Joshi et al. (10)]) at 100–120◦C. However, compound 14 did not re-
act with thiol 12a: a weak electrophile 14 decomposed slowly even under milder
conditions (DBU, MeCN, 70◦C) and only traces of 15a were formed.
Attempts to reduce formation of elimination product 16 were unsuccessful.
No reaction was observed without DBU. The use of weaker amino bases instead of
DBU for the interaction of 13c and mercaptan 12a in DMF resulted in recovery of
starting mesylate 13c (48-h heating with pyridine) or in incomplete reaction (72-h
heating with diisopropylamine led to a 1:1:2 mixture of the substitution product
15a, the elimination product 16, and the starting material).
Unfortunately, nucleosides15fand15gpossessingastrongnucleophilicgroup
were unstable, possibly because of ncleophilic attack of the SH group on the
anomeric position of the ring; they were not isolated, since appreciable decom-
position occurred even on an inert reverse phase HPLC column, and only their
yield was estimated (by NMR).
Since one of the ribose ring conformations, namely the North (N) conforma-
tion, is considered important for RT and DNApol assisted catalysis [see

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97
Scheme 2. Selected NOE interactions and conformational equilibrium for nucleoside 17b.
Schinazi (1)], we also examined deoxynucleoside 17b by NMR. NOESY experi-
ments allowed us to estimate qualitatively a S↔N conformational equilibrium (11)
for 3ꢀ-alkylthio-3ꢀ-deoxythmidines (see Scheme 2 for selected NOE interactions).
As in the case of 3ꢀ-selenocyanate deoxythymidines (6), NOE interactions
between the olefinic proton of the pyrimidine ring and the H-3ꢀ-furanose proton
are observed. Thus, the N-conformation of the deoxyribose ring and the anti-
conformation of the nucleobase are appreciably populated for 17b. Unfortunately,
we were unable to study the S↔N equilibrium for diselenides 6a,b because of
overlapping ring proton signals.
3ꢀ-Substituted nucleoside 17a, containing a remote nucleophilic group,
showed no remarkable anticancer activity in cytotoxicity experiments in 60 human
cancer cell lines (E. Sausville personal communication NCI’s primary anticancer
screen, Bethesda (12). In contrast, masked 3ꢀ-selenol 6b demonstrated significant
cytostatic activity in preliminary studies in colon and breast cancer cells in similar
concentrations as fluorouracil (e.g., for colon cancer the cell cytotoxicity is 75
and 70% for a 45 µg/mL concentration of 6b and fluorouracil, respectively) (12 ).
Detailed anticancer studies for 6b as well as other new nucleoside heteroanalogs
will be reported separately.
EXPERIMENTAL
Materials and methods. All reaction have been carried out in anhydrous
solventsunderadryargonatmosphere. ThereactionsweremonitoredbyTLC. Flash
column chromatography was performed using Merck 60 silica gel, washed with a
3:1 mixture of CHCl3–EtOH followed by prolonged washing with eluent mixture.
Analytical separations were performed in a gradient regime on a Waters 501 HPLC
instrument equipped with a semipreparative Merck RP18 column. The purity of
new compounds was determined by 1H and 13C NMR, HPLC as well as TLC (for
diselenides) in 2–3 chromatographic systems. NMR spectra have been recorded on
Brucker AM-300 as well as Brucker-600 spectrometers. Mass spectra (including
high-resolution mass spectra) were obtained on a Fisons VG AutoSpec instrument,
using chemical ionization (by i-BuH or CH4) or fast atom bombardment (glycerol
matrix) methods. Detected MH+ values are given for 80Se-containing ions. The
analytical spectral data for related compounds (e.g., 15a–g) are given for selected
examples (e.g., for compound 15d).

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BELOSTOTSKII ET AL.
2ꢀ-O,3ꢀ-O-Isopropylidene-5ꢀ-deoxyuridine-5ꢀ-selenocyanate (2). A solu-
tion of 140 mg (0.085 mL, 0.77 mmol) of tresyl chloride in 3 ml of CHCl3 was
added dropwise at −20◦C to a mixture of 200 mg (0.70 mmol) of 2ꢀ-O,3ꢀ-O-
isopropylideneuridine (Sigma) and 61 mg (0.06 mL, 0.77 mmol) of dry pyridine in
3 ml of CHCl3. After 2 h the mixture was allowed to warm to 0◦C, washed with ice-
water, cold 1% HCl, 1% NaHCO3, and water. The CHCl3 solution was dried over
MgSO4 and filtered to a flask with 364 mg (1.05 mmol) of tetrabutylammonium
selenocyanate (6). The mixture was stirred 48 h at room temperature, evaporated
and chromatographed. Yield: 73 mg (28%). 1H NMR (CDCl3): 1.36 (s, 3H; Me),
1.58 (s, 3H; Me), 3.86 (AB-part of ABX system, 2H, 17.9 and 3.6 Hz; H-5ꢀ, H-5ꢀꢀ),
4.30 (m, 1H; H-4ꢀ), 4.99 (m, 2H; H-2ꢀ, H-3ꢀ), 5.56 (d, 1H, 1.5 Hz; H-1ꢀ), 5.76 (dd,
1H, 9.2 and 1.5 Hz; 5-H), 7.37 (d, 1H, 9.2 Hz; 6-H). Mass spectrum (m/z): 373
(MH+).
5ꢀ-Deoxythymidine-5ꢀ-selenocyanate (5b) and bis(5ꢀ-deoxythymidine)-
5ꢀ,5ꢀ-diselenide (8b). A mixture of 100 mg (0.27 mmol) of acetate 5a (6), 4 mg
(0.03 mmol) of K2CO3, and 8 mL of MeOH was stirred 48 h at room tempera-
ture and evaporated with 2 g of silica. The silica was added carefully to the silica
gel of chromatography column, and chromatography separation (gradient EtOAc
– EtOAc/MeOH 7:1) afforded 40 mg of deacylation product 5b (44% yield) and
15 mg of diselenide 8b (20% yield). Compound 5b – 1H NMR (acetone-d6): 1.85 (d,
3H, 0.7 Hz; 5-Me), 2.33 (ddd, 1H, 10.0, 6.0, and 3.5 Hz; H-2ꢀ), 2.45 (m, 1H; H-2ꢀꢀ),
ꢀ
ꢀꢀ
ꢀ
ꢀ
ꢀ
ꢀꢀ
3.55 (ABpartof ABX system, 2H, J5 ,5 = 12.8Hz, J4 ,5 = 7.3Hz, J4 ,5 = 5.2Hz;
H-5ꢀ, H-5ꢀꢀ), 4.20 (m, 1H; H-4ꢀ), 4.50 (m, 1H; H-3ꢀ), 6.35 (dd, 1H, 7.0 Hz; H-1ꢀ),
7.53 (q, 1H, 0.7 Hz; H-6). Mass spectrum (m/z): 331 (MH+). Compound 8b – 1H
NMR (CD3OD): 1.89 (s, 6H, 5-Me), 2.28 (dd, 2H, 5.9 and 4.9 Hz; H-2ꢀ), 3.27 (m,
2H; H-2ꢀꢀ), 3.62 (m, 4H; H-5ꢀ, H-5ꢀꢀ), 4.09 (m, 2H; H-4ꢀ), 4.33 (m, 2H; H-3ꢀ), 6.25
(dd, 2H, 11.7 and 11.7 Hz; H-1ꢀ), 7.49 (s, 2H; 6-H). Mass spectrum (m/z): 611
(MH+).
Bis(5ꢀ-O-tert-butyldimethylsilyl-3ꢀ-deoxythymidine)-3ꢀ-β-3ꢀ-β-diselenide
(7). To a solution of 57 mg (0.1 mmol) of selenocyanate 4 (6) in 2 mL of EtOH,
1 mg (0.025 mmol) of NaBH4 was added at 0◦C. After 1 h the mixture was evap-
orated, water and CHCl3 were added, and organic phase was dried over MgSO4,
filtered, and evaporated. Column chromatography afforded 12 mg of 7 (24% yield).
1H NMR (CDCl3): 0.15 (s, 12H; SiMe2), 0.95 (s, 18H; SiCMe3); 1.95 (d, 6H, 1.1
Hz; 5-Me), 2.24 (m, 2H; H-2ꢀ), 2.80 (ddd, 2H, 12.0, 7.0, and 5.1 Hz; H-2ꢀꢀ), 3.92
(m, 6H; H-3ꢀ, H-5ꢀ, H-5ꢀꢀ), 4.35 (m, 2H; H-4ꢀ), 6.04 (dd, 2H, 8.5 and 5.1 Hz; H-1ꢀ),
7.52 (q, 2H, 1.1 Hz; H-6). 13C NMR (CDCl3): −5.27 (SiMe2), 12.53 (5-Me), 18.24
(SiCMe3), 26.12 (SiCMe3), 41.41 (C-2ꢀ), 45.29 (C-3ꢀ), 64.95 (C-5ꢀ), 81.20, 83.32
(C-1ꢀ and C-4ꢀ), 111.06 (C-5), 134.97 (C-6), 150.77 (C-2), 168.74 (C-4). High-
resolution mass spectrum (FAB+) calcd. for C32H55N4O8Se2Si2 (MH+): 839.190.
Found: 839.167.
Bis(deoxynucleoside) diselenides by NaBH(AcO)3-assisted reduction
(general procedure). A mixture of 0.05 mmol of deoxynucleoside selenocyanate,
0.05 mmol of NaBH(AcO)3, and 2 mL of EtOH was stirred 2 h at room temperature

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3ꢀ -SUBSTITUTED 3ꢀ -DEOXYTHYMIDINES
99
and evaporated. The residue was washed with water and i-PrOH and dried over
P2O5.
Bis(3ꢀ-O-acetyl-5ꢀ-deoxythymidine)-5ꢀ,5ꢀ-diselenide(8a). Itwasobtained
in 98% yield from bselenocyanate 5a (6). 1H NMR (CDCl3): 1.95 (d, 6H, 0.9 Hz;
5-Me), 2.10 (s, 6H; MeCO), 2.40 (m, 4H; H-2ꢀ, H-2ꢀꢀ), 3.45 (m, 4H; H-5ꢀ, H-5ꢀꢀ),
4.25 (m, 2H; H-4ꢀ), 5.25 (m, 2H; H-3ꢀ), 6.20 (dd, 2H, 6.9 Hz; H-1ꢀ), 8.05 (q, 2H,
0.9 Hz; H-6). Mass spectrum (m/z): 695 (MH+).
Bis(2ꢀ-O,3ꢀ-O-isopropylidene-5ꢀ-deoxyuridine)-5ꢀ,5ꢀ-diselenide (9). It
was obtained in 86% yield from selenocyanate 2. 1H NMR (CDCl3): 1.37 (s, 6H;
Me), 1.58 (s, 6H; Me), 3.79 (m, 4H; H-5ꢀ, H-5ꢀꢀ), 4.37 (m, 2H; H-4ꢀ), 4.94 (m, 4H;
H-2ꢀ, H-3ꢀ), 5.69 (d, 2H, 2.7 Hz; H-1ꢀ), 5.75 (d, 2H, 7.4 Hz; H-5), 7.34 (d, 2H, 7.4
Hz; H-6).
Bis(3ꢀ-deoxythymidine)-3ꢀ-α-,3ꢀ-α-diselenide (6b). The residue, which
was obtained according to the general procedure (see preceding) from seleno-
cyanate 3 (6), was dissolved in 80% AcOH, refluxed 2 h, evaporated to a small
volume, reevaporated with EtOH (5 × 50 mL), and chromatographed. Compound
6b (74% yield) – 1H NMR (acetone-d6): 1.80 (s, 6H; Me), 2.55 (m, 4H; H-2ꢀ and
H-2ꢀꢀ), 3.95 (m, 8H; H-3ꢀ, H-4ꢀ, H-5ꢀ, H-5ꢀꢀ), 6.17 (dd, 2H; H-1ꢀ), 7.93 (s, 2H; H-
6). 13C NMR (acetone-d6): 12.53 (5-Me), 30.07 (C-2ꢀ), 37.12 (C-3ꢀ), 61.47 (C-5ꢀ),
85.27, 88.10 (C-1ꢀ and C-4ꢀ), 110.26 (C-5), 137.01 (C-6), 151.25 (C-2), 164.27
(C-4). High-resolution mass spectrum (FAB+) calcd. for C20H27N4O8Se2 (MH+):
611.016. Found: 611.194.
3ꢀ-β-O-Mesyl-5ꢀ-O-tert-butyldimethylsilylthymidine (13c). The pro-
cedure was analogous to that for preparation of mesylate 13b [see Bera et al.
(10)]. Yield: 90%. 1H NMR (CDCl3): 0.10 (s, 6H; SiMe2), 0.92 (s, 9H; SiCMe3);
1.95 (d, 3H, 1.1 Hz; 5-Me), 2.43 (m, 1H, H-2ꢀ), 2.87 (m, 1H, H-2ꢀꢀ), 3.05 (s, 3H;
MeS), 3.9–4.1 (m, 3H; H-4ꢀ, H-5ꢀ, H-5ꢀꢀ), 5.26 (m, 1H; H-3ꢀ), 6.32 (dd, 1H; H-1ꢀ),
7.42 (s, 1H; H-6).
Preparation of 3ꢀ-α-S-alkyl-3ꢀ-deoxythymidines (general procedure).
A
mixture of 6 mmol of mercaptan, 2.5 mmol of DBU, and 2 mL of DMF was
heated at 60◦C for 10 min. A solution of 1 mmol of mesylate 13b [see Bera et al.
(10)] or 13c was added and the mixture was kept for 5–20 h at this temperature.
EtOAc and water were added at 25◦C, the organic phase was dried over MgSO4
and chromatographed. The yields are shown in Figure 2.
5ꢀ-O-Trityl-3ꢀ-α-S-(N-acetyl-2-aminoethyl)-3ꢀ-deoxythymidine (15d). It
was obtained from 13b and 12b. 1H NMR (CDCl3): 1.45 (d, 3H, 0.9 Hz; 5-Me),
1.95 (s, 3H, MeCO), 2.3–2.6 (m, 2H; H-2ꢀ, H-2ꢀꢀ), 2.55 (t, 2H, 6.6 Hz; Ch2S), 3.34
(m, 3H; H-5ꢀ, CH2N), 3.67 (m, 2H; H-3ꢀ, H-5ꢀꢀ), 3.95 (dt, 1H, 7.6 Hz, 3.0 Hz;
H-4ꢀ), 6.21 (dd, 1H, 6.8 Hz, 4.0 Hz; H-1ꢀ), 7.2–7.4 (m, 15H; Ph), 7.75 (q, 1H,
0.9 Hz; 6-H). 13C NMR (CDCl3): 11.58 (5-Me), 22.56 (MeCO), 30.81 (C-2ꢀ),
38.59 (CH2S), 40.02 (CH2N), 40.43 (C-3ꢀ), 62.01 (C-5ꢀ), 84.33, 84.84 (C-1ꢀ, C-4ꢀ),
86.75 (Ph), 110.33 (C-5), 126.5–128.2 (Ph), 135.30 (C-6), 142.85 (Ph), 150.29
(C-2), 163.99 (C-4), 206.76 (CO). High-resolution mass spectrum (FAB+) calcd.
for C33H36N3O5S (MH+): 586.2376. Found: 586.2310.

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BELOSTOTSKII ET AL.
Deprotection of 5ꢀ-O-protected 3ꢀ-α-S-alkyl-3ꢀ-deoxythymidines (general
procedure). A mixture of 0.5 mmol of 15a–d and 5 mL of 80% AOH was refluxed
1–2 h, evaporated, reevaporated several times with EtOH and once with toluene,
and chromatographed.
3ꢀ-α-S-(N-acetyl-2-aminoethyl)-3ꢀ-deoxythymidine (17d). It was obtain-
1
ed from 15d in 81% yield. H NMR (CD3OD): 1.85 (s, 3H; 5-Me), 1.96 (s, 3H;
MeCO), 2.44 (m, 2H, H-2ꢀ, H-2ꢀꢀ), 2.75 (t, 2H, 6.7 Hz; CH2S), 3.37 (t, 2H; 6.7 Hz;
CH2N), 3.50 (m, 1H; H-5ꢀ), 3.87 (m, 3H; H-3ꢀ, H-4ꢀ, H-5ꢀꢀ), 6.13 (dd, 1H, 7.0 and
4.2 Hz; H-1ꢀ), 7.9 (s, 1H; H-6). Mass spectrum (m/z): 344 (MH+).
ACKNOWLEDGMENTS
We are grateful for support of this research by the Israel Ministry of Science
and Technology (Grant 1471-1-99), the governmental KAMEA Program, and the
Marcus Center for Pharmaceutical and Medicinal Chemistry. We thank Dr. J. G.
Hengstler, University of Mainz, for bioassays on nucleoside 6b.
REFERENCES
1. Schinazi, R.F. Perspect. in Drug Discovery and Design 1993, 1, 151–80; DeClercq,
E. AIDS Res. Human Retrovir. 1992, 8, 119–34; Arnold, E.; Arnold, G.F. Adv. Virus
Res. 1993, 39, 1–87; DeClercq, E. Collect. Czech. Chem. Comm. 1998, 63, 449–79;
Ng, K.-M.E.; Orgel, L.E. J. Med. Chem. 1989, 32, 1754–57; Lin, T.-S.; Prusoff, W.H.
J. Med. Chem. 1978, 20, 109–112; Kedar, P.S.; Abotts, J.; Kovacs, T.; Lesiak, K.;
Torrence, P.; Wilson, S.H. Biochemistry 1990, 29, 3603–611.
2. Chidgeavadze, Z.G.; Beabealashvilli, R. Sh.; Krayevsky, A.; Kuchanova, M. Biochem.
Biophys. Acta 1986, 868, 145–52; Huryn, D.H.; Okabe, M. Chem. Rev. 1992, 92,
1745–68; Tetko, I.V.; Tanchuk, V. Yu.; Chentsova, N.P.; Antonenko, S.V.; Poda, G.I.;
Kuchar, V.P.; Luik, A.I. J. Med. Chem. 1994, 37, 2520–26; Herdewijn, P.; Balzarini,
J.; DeClercq, E.; Pauwels, R.; Baba, M.; Broder, S.; Vanderhaeghe, H. J. Med. Chem.
1987, 30, 1270–78.
3. Yuzhakov, A.; Chidgeavadze, Z. G.; Beabealashvilli, R. Sh. FEBS Lett. 1992, 306,
185–88.
4. Schreiber, S.L.; Ikemoto, N. Tetrahedron Lett. 1988, 29, 3211–14.
5. Domenico, P.; Salo, R.J.; Novick, S.G.; Schoch, P.E.; vanHorn, K.; Cuhna, B.A. An-
timicrob. Agents Chemother. 1997, 41, 1697–703; Johannsen, B.; Scheunermann, B.;
Spies, H.; Brust, P.; Wober, J.; Syhre, R.; Pietzsch, H.-J. Nucl. Med. Biol. 1996, 23,
429–38; Kati, W.M.; Johnson, K.A.; Jerva, L.F.; Anderson, K.S. J. Biol. Chem. 1992,
36, 25988–97; Wohrl, B.M.; Tantillo, C.; Arnold, E.; Le Grice, S.F. J. Biochemistry
1995, 34, 5343–50.
6. Belostotskii, A.M.; Lexner, J.; Hassner, A. Tetrahedron Lett. 1999, 40, 1184–87.
7. Bjornstedt, M.; Hamberg, M.; Kumar, S.; Xue, J.; Holmgren, A. J. Biol. Chem., 1995
270, 11761–64.
8. Wozniak, L.A.; Sochaki, M.; Kageyama, S.; Stec, W.J. Biorg. Med. Chem. Lett., 1994
4, 1033–36.

ORDER
REPRINTS
3ꢀ -SUBSTITUTED 3ꢀ -DEOXYTHYMIDINES
101
9. Salama, P.; Charles, B. Tetrahedron Lett. 1995, 35, 5711–14; Witczak, Z.J.; Czernecki,
S. Adv. Carbohydr. Chem Biochem. 1998, 53, 143–99; Krief, A.; Delmotte, C.;
Dumont, W. Tetrahedron 1997, 53, 12147–58; Krief, A.; Delmotte, C.; Dumont, W.
Angew. Chem., Int. Ed. 2000, 39, 1672–99.
10. Bera, S.; Sakthivel, K.; Pathak, T.; Langley, G.L. Tetrahedron 1995, 51, 7857–66;
Joshi, B.V.; Reese, C.B. Tetrahedron Lett. 1992, 33, 2371–74; Joshi, B.V.; Rao, T.S.;
Reese, C.B. J. Chem. Soc. Perkin Trans. 1992, 1, 2537–44.
11. Thibaudeau, C.; Plavec, J.; Garg, N.; Papchikhin, A.; Chattopadhyaya, J. J. Am. Chem.
Soc. 1994, 116, 4038–43; Plavec, J.; Garg, N.; Chattopadhyaya, J. J. Chem. Soc.,
Chem. Comm. 1993, 1011–14; Thibaudeau, C. Stereoelectronic Effects in Nucleosides
and Nucleotides; Acta Universitatis Upsaliensis: Uppsala, 1999.
12. Unpublished results: Hengstler, J.G., University of Mainz (Using a Microplate ATP-
Assay: Andreotti, P.E.; Cree, I.A.; Kurbacher, C.M.; Hartmann, D.M.; Linder, D.;
Harel, G.; Gleiberman, I.; Caruso, P.A.; Ricks, S.H.; Untch, M. Cancer Res. 1995 55,
5276–82).
Received June 29, 2000
Accepted September 29, 2000

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