J . Org. Chem. 1999, 64, 4533-4536
4533
providing N-1-(R-naphthyl)ethyl-O-methylphosphorami-
dothioate (2), which upon treatment with methyl iodide
gave (SP,RC)-O,S-dimethyl-N-1-(R-naphthyl)ethylphos-
phoramidothioate.6 Thus, a new approach to the stereo-
controlled synthesis of O-alkyl-N-alkylphosphoramido-
thioates has been demonstrated. In light of these results,
it was tempting to test the suitability of 2-oxo-1,3,2-
oxathiaphospholane analogues of 3′-amino-2′,3′-dide-
oxyribonucleosides for synthesis of N3′fP5′ oligos.
Syn th esis of
2′,3′-Did eoxyr ibon u cleosid e-3′-N-(2-oxo-
1,3,2-oxa th ia p h osp h ola n es) a n d Th eir
Rea ction s w ith 5′-OH Nu cleosid es a n d
F lu or id e Ion
J anina Baraniak, Dariusz Korczyn˜ski, and
Wojciech J . Stec*
Polish Academy of Sciences, Centre of Molecular and
Macromolecular Studies, Department of Bioorganic
Chemistry, Sienkiewicza 112, 90-363 L-o´dz´, Poland
Resu lts a n d Discu ssion
The reaction of 5′-O-DMT-base-protected-3′-amino-
2′,3′-dideoxyribonucleosides 3a -d with an equimolar
amount of 2-chloro-4,4-spiro(pentamethylene-1,3,2-ox-
athiaphospholane) (4)5d resulted in the formation of an
intermediate phosphoramidite (5a -d ), which was oxi-
dized without isolation by means of tert-butyl hydroper-
oxide (TBHP) into the corresponding 5′-O-DMT-base-
protected-2′,3′-dideoxyribonucleoside-3′-N-(2-oxo-4,4-
spiro(pentamethylene-1,3,2-oxathiaphospholane)) (6a -
d , Scheme 1).
Compounds 6a -d have been isolated from the reaction
mixture by column chromatography on silica gel as a
mixture of diastereomers and have been characterized
by 31P NMR and FAB-MS (Table 1).
Condensation of 6a with an equimolar amount of 3′-
O-acetylthymidine in the presence of a 5-fold molar
excess of triethylamine in acetonitrile solution led, after
24 h, to dithymidine N3′fP5′-phosphoramidate (7a , 70%
yield). However, when 1,8-diazabicyclo[5.4.0]undec-1-ene
(DBU) was used instead of triethylamine, the above
condensation process occurred much faster and the
desired product 7a was obtained in 85% yield after 30
min.
This result prompted us to attempt a solid-support
synthesis of dinucleoside N3′fP5′ phosphoramidates
8a -d using 6a -d as the substrates (Scheme 2). As
described by Brown et al.,7 DBU partially cleaves the
standard succinoyl linker and releases the dinucleotide
from the solid support. Therefore, 5′-O-DMT-thymidine
was immobilized on controlled pore glass via a DBU-
resistant sarcosinyl-succinoyl linker.5c The optimized
conditions for 1 µM solid-phase synthesis were as fol-
lows: 20-fold molar excess of oxathiaphospholane mono-
mer 6a -d , 50-fold molar excess of DBU, coupling time
800 s. Compound 8a was obtained in 93% yield as
calculated from the DMT cation assay. In an analogous
way, syntheses of compounds 8b-d were performed and
the results are presented in Table 2.
Received November 10, 1998
In tr od u ction
During the past few years, Gryaznov et al. reported in
numerous papers that analogues of oligodeoxyribonucle-
otides, where the 3′-oxygen of incorporated deoxyribo-
nucleosides is replaced by an NH function, possess
interesting properties of hybridization to complementary
strands of DNA and RNA. Moreover, these N3′fP5′ DNA
analogues, with relatively low avidity for cellular pro-
teins, appeared to possess high affinity to double-
stranded DNA forming stable DNA triplexes.1 For these
reasons, N3′fP5′ oligos became of special interest for
their use in antisense2 and antigene3 strategies targeting
the inhibition of biosynthesis of preselected proteins,
coded by corresponding mRNA and DNA. Although
several methods of synthesis of N3′fP5′ oligos have been
developed,1b-d,4 their accessibility remains limited. In the
search for new preparative methodology, we revisited our
interest in the chemistry of 2-alkylamino-2-thio-1,3,2-
oxathiaphospholanes.5b In the course of our studies on
the synthesis, structure, and stereochemistry of base-
assisted alcoholysis of diastereomeric (RP,RC)- and
(SP,RC)-1-(R-naphthyl)ethylamino-2-thio-1,3,2-oxathiaphospho-
lanes (1), we have found that methanolysis of (RP,RC)-1
in the presence of triethylamine occurred smoothly,
(1) (a) Gryaznov, S. M.; Letsinger, R. L. Nucleic Acids Res. 1992,
20, 3403. (b) Gryaznov, S.; Chen, J .-K. J . Am. Chem. Soc. 1994, 116,
3143. (c) Chen, J .-K.; Schultz, R. G.; Lloyd, D. H.; Gryaznov, S. M.
Nucleic Acids Res. 1995, 23, 2661. (d) Schultz, R. G.; Gryaznov, S. M.
Nucleic Acids Res. 1996, 24, 2966. (e) Mignet, N.; Gryaznov, S. M.
Nucleic Acids Res. 1998, 26, 431. (f) Barsky, D.; Colvin, M. E.; Zon,
G.; Gryaznov, S. M. Nucleic Acids Res. 1997, 25, 830. (g) Giovannangeli,
C.; Perrouault, L.; Escude, Ch.; Gryaznov, S.; Helene, C. J . Mol. Biol.
1996, 261, 386. (h) Ding, D.; Gryaznov, S. M.; Lloyd, D. H.; Chan-
drasekaran, S.; Yao, S.; Ratmeyer, L.; Pan, Y.; Wilson, W. D. Nucleic
Acids Res. 1996, 24, 354; Tereshko, V.; Gryaznov, S.; Egli, M. J . Am.
Chem. Soc. 1998, 120, 269. (i) Testa, S. M.; Gryaznov, S. M.; Turner,
D. H. Biochemistry 1998, 37, 9379. (j) Ding, D.; Gryaznov, S. M.;
Wilson, W. D. Biochemistry 1998, 37, 12082. (k) Gryaznov, S. M.;
Winter, H. Nucleic Acids Res. 1998 26, 4160. (l) Gryaznov, S. M.; Lloyd,
D. H.; Chen, J .-K.; Schultz, R. G.; DeDionisio, L. A.; Ratmeyer, L.;
Wilson, W. D. Proc. Natl. Acad. Sci. U.S.A. 1995, 92, 5798. (m)
Gryaznov, S. M.; Sko´rski, T.; Cucco, C.; Nieborowska-Sko´rska, M.;
Chin, C. Y.; Lloyd, D.; Chen, J .-K.; Koziołkiewicz, M.; Calabretta, B.
Nucleic Acids Res. 1996, 24, 1508.
(2) Uhlman, E.; Peyman, A. Chem. Rev. 1990, 90, 544.
(3) Thuong, N. T.; Helene, C. Angew. Chem., Int. Ed. Engl. 1993,
32, 666.
(4) (a) Nelson, J . S.; Fearon, K. L.; Nguyen, M. Q.; McCurdy, S. N.;
Frediani, J . E.; Foy, M. F.; Hirschbein, B. L. J . Org. Chem. 1997, 62,
7278. (b) Baraniak, J .; Korczyn˜ski, D.; Kaczmarek, R.; Wasilewska,
E. Nucleosides Nucleotides 1998, 17, 1347. (c) Fearon, K. L.; Hirschbein,
B. L.; Nelson, J . S.; Foy, M. F.; Nguyen, M. Q.; Okruszek, A.; McCurdy,
S. M.; Frediani, J . E.; DeDionisio, L. A.; Raible, A. M.; Cagle, E. N.;
Boyd, V. Nucleic Acids Res. 1998, 26, 3813.
However, attempts at elongation of the oligonucleotide
chain were not successful. The yield of the second
(5) (a) Stec, W. J .; Grajkowski, A.; Koziołkiewicz, M.; Uznan˜ski, B.
Nucleic Acids Res. 1991, 19, 5883. (b) Uznan˜ski, B.; Grajkowski, A.;
Krzyz˘ anowska, B.; Kaz´mierkowska, A.; Stec, W. J .; Wieczorek, M. W.;
Błaszczyk, J . J . Am. Chem. Soc. 1992, 114, 10197. (c) Stec, W. J .;
Grajkowski, A.; Karwowski, B.; Kobylan˜ska, A.; Koziołkiewicz, M.;
Misiura, K.; Okruszek, A.; Wilk, A.; Guga, P.; Boczkowska, M. J . Am.
Chem. Soc. 1995, 117, 12019. (d) Stec, W. J .; Karwowski, B.; Bocz-
kowska, M.; Guga, P.; Koziołkiewicz, M.; Sochacki, M.; Wieczorek, M.
W.; Błaszczyk, J . J . Am. Chem. 1998, 120, 7156.
(6) Kotyn˜ski, A.; Lesiak, K.; Stec, W. J . Pol. J . Chem. 1979, 53, 2403.
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10.1021/jo982240r CCC: $18.00 © 1999 American Chemical Society
Published on Web 05/18/1999