Recent Advances in the Chemical Synthesis of RNA

Serge L. Beaucage1, Colin B. Reese2

1 Food and Drug Administration, Bethesda, Maryland, 2 King's College London, London, United Kingdom
Publication Name:  Current Protocols in Nucleic Acid Chemistry
Unit Number:  Unit 2.16
DOI:  10.1002/0471142700.nc0216s38
Online Posting Date:  September, 2009
GO TO THE FULL TEXT: PDF or HTML at Wiley Online Library

Abstract

As a consequence largely of recent developments in RNA interference (RNAi) research, the availability of rapid and efficient methods for the chemical synthesis of RNA sequences has become a matter of considerable urgency. This unit is concerned mainly with work that has been carried out, especially in the past decade, on the design of new and improved methods of RNA synthesis. The main criteria for the choice of protecting groups for the 2′‐hydroxy functions of the ribonucleoside building blocks, which is arguably the most crucial strategic decision to be made, are discussed. A number of new ether‐, acetal‐, orthoester‐, and ester‐based 2′‐protecting groups are described and their application, mainly in phosphoramidite‐based solid‐phase synthesis, is discussed in some detail. Brief consideration is also given to solution‐phase RNA synthesis, which may well prove to be of great importance if a systemic drug is developed and multikilogram quantities of synthetic RNA sequences are required. Curr. Protoc. Nucleic Acid Chem. 38:2.16.1‐2.16.31. © 2009 by John Wiley & Sons, Inc.

Keywords: 2′‐hydroxyl protecting groups; ether protecting groups; acetal protecting groups; ester protecting groups; ribonucleoside phosphoramidites; phosphitylation; solid‐phase synthesis; solution‐phase synthesis

     
 
GO TO THE FULL PROTOCOL:
PDF or HTML at Wiley Online Library

Table of Contents

  • Introduction
  • Main Criteria for the Selection of 2′‐Protecting Groups
  • Protection of the 2′‐Hydroxy Function in the Solid‐Phase Synthesis of Oligoribonucleotides
  • Protection of the 2′‐Hydroxy Function in the Solution‐Phase Synthesis of Oligoribonucleotides
  • Conclusions
  • Literature Cited
  • Figures
     
 
GO TO THE FULL PROTOCOL:
PDF or HTML at Wiley Online Library

Materials

GO TO THE FULL PROTOCOL:
PDF or HTML at Wiley Online Library

Figures

Videos

Literature Cited

Literature Cited
   Adams, S.P., Kavka, K.S., Wykes, E.J., Holder, S.B., and Gallupi, G.R. 1983. Hindered dialkylamino nucleoside phosphite reagents in the synthesis of two DNA 51‐mers. J. Am. Chem. Soc. 105:661‐663.
   Beaucage, S.L. 2008. Solid‐phase synthesis of siRNA oligonucleotides. Curr. Opin. Drug Discov. Dev. 11:203‐216.
   Beaucage, S.L. and Caruthers, M.H. 1981. Deoxynucleoside phosphoramidites—A new class of key intermediates for deoxypolynucleotide synthesis. Tetrahedron Lett. 22:1859‐1862.
   Beaucage, S.L. and Iyer, R.P. 1992. Advances in the synthesis of oligonucleotides by the phosphoramidite approach. Tetrahedron 48:2223‐2311.
   Bumcrot, D., Manoharan, M., Koteliansky, V., and Sah, D.W.Y. 2006. RNAi therapeutics: A potential new class of pharmaceutical drugs. Nat. Chem. Biol. 2:711‐719.
   Capaldi, D.C. and Reese, C.B. 1994. Use of the 1‐(2‐fluorophenyl)‐4‐methoxypiperidin‐4‐yl (Fpmp) and related protecting groups in oligoribonucleotide synthesis: Stability of internucleotide linkages to aqueous acid. Nucleic Acids. Res. 22:2209‐2216.
   Cieślak, J., Kauffman, J.S., Kolodziejski, M.J., Lloyd, J.R., and Beaucage, S.L. 2007. Assessment of 4‐nitrogenated benzyloxymethyl groups for 2′‐hydroxyl protection in solid‐phase RNA synthesis. Org. Lett. 9:671‐674.
   Cieślak, J., Grajkowski, A., Kauffman, J.S., Duff, R.J., and Beaucage, S.L. 2008. The 4‐(N‐dichloroacetyl‐N‐methylamino)benzyloxymethyl group for 2′‐hydroxyl protection of ribonucleosides in the solid‐phase synthesis of oligoribonucleotides. J. Org. Chem. 73:2774‐2783.
   Dahl, B.H., Bjergårde, K., Henriksen, L., and Dahl, O. 1990. A highly reactive, odourless substitute for thiophenol/triethylamine as a deprotection reagent in the synthesis of oligonucleotides and their analogues. Acta Chem. Scand. 44:639‐641.
   Damha, M.J. and Ogilvie, K.K. 1993. Oligoribonucleotide synthesis. In Methods in Molecular Biology, Vol 20: Protocols for Oligonucleotides and Analogs (S. Agrawal, ed.) pp. 81‐114. Humana Press, Totowa, N.J.
   deBear, J.S., Hayes, J.A., Koleck, M.P., and Gough, G.R. 1987. A universal glass support for oligonucleotide synthesis. Nucleosides Nucleotides 6:821‐830.
   Donga, R.A., Chan, T.‐H., and Damha, M.J. 2007. Ion‐tagged synthesis of an oligoribonucleotide pentamer – The continuing versatility of TBDMS chemistry. Can. J. Chem. 85:274‐282.
   Faja, M., Reese, C.B., Song, Q., and Zhang, P.‐Z. 1997. Facile preparation of acetals and enol ethers derived from 1‐arylpiperidin‐4‐ones. J. Chem. Soc. Perkin Trans. 1:191‐194.
   Gasparutto, D., Livache, T, Bazin, H., Duplaa, A.M., Guy, A., Khorlin, A., Molko, D., Roget, A., and Téoule, R. 1992. Chemical synthesis of a biologically active natural tRNA with its minor bases. Nucleic Acids Res. 20:5159‐5166.
   Gough, G.R., Miller, T.J., and Mantick, N.A. 1996. p‐Nitrobenzyloxymethyl: A new fluoride‐removable protecting group for ribonucleoside 2′‐hydroxyls. Tetrahedron Lett. 37:981‐982.
   Hartsel, S.A., Kitchen, D.E., Scaringe, S.S., and Marshall, W.S. 2005. RNA oligonucleotide synthesis via 5′‐silyl‐2′‐orthoester chemistry. In Methods in Molecular Biology, Vol 288: Oligonucleotide Synthesis: Methods and Applications (P. Herdewijn, ed.) pp.33‐49. Humana Press, Totowa, N.J.
   Hayakawa, Y., Wakabayashi, S., Kato, H., and Noyori, R. 1990. The allylic protection method in solid‐phase oligonucleotide synthesis. An efficient preparation of solid‐anchored DNA oligomers. J. Am. Chem. Soc. 112:1691‐1696.
   Höbartner, C., Kreutz, C., Flecker, E., Ottenschläger, E., Pils, W., Grubmayr, K., and Micura, R. 2003. The synthesis of 2′‐O‐[(triisopropylsilyl)oxy]methyl (TOM) phosphoramidites of methylated ribonucleosides (m1G, m2G, m22G, m1I, m3U, m4C, m6A, m62A) for use in automated RNA solid‐phase synthesis. Monatsh. Chem. 134:851‐873.
   Hogrefe, R.I., McCaffey, A.P., Borozdina, L.U., McCampbell, E.S., and Vaghefi, M.M. 1993. Effect of excess water on the desilylation of oligoribonucleotides using tetrabutylammonium fluoride. Nucleic Acids Res. 21:4739‐4741.
   Iyer, R.P. and Beaucage, S.L. 1999. Oligonucleotide synthesis. In Comprehensive Natural Product Chemistry, Vol. 7: DNA and Aspect of Molecular Biology (D.H.R. Barton, K. Nakanishi, O. Meth‐Cohn, and E.T. Kool, eds.) pp. 105‐152. Elsevier Science, Oxford.
   Komatsu, Y. and Othsuka, E. 1999. Chemical synthesis of RNA (including RNA with unusual constituents). In Comprehensive Natural Products Chemistry, Vol. 6: Prebiotic Chemistry, Molecular Fossils, Nucleosides, and RNA (D.H.R. Barton, K. Nakanishi, O. Meth‐Cohn, D. Söll, S. Nishimura, and P. B. Moore, eds.) pp. 81‐96. Elsevier Science, Oxford.
   Lackey, J.G. and Damha, M.J. 2008. The acetal levuliny ester (ALE) group for the 2′‐hydroxyl protection of ribonucleosides and the synthesis of oligoribonucleotides. Nucleic Acids Symp. Ser. 52:35‐36.
   Lackey, J.G., Sabatino, D., and Damha, M.J. 2007. Solid‐phase synthesis and on‐column deprotection of RNA from 2′‐ (and 3′‐)O‐levulinated (Lv) ribonucleoside monomers. Org. Lett. 9:789‐792.
   Lavergne, T., Bertrand, J.‐R., Vasseur, J.‐J., and Debart, F. 2008a. A base‐labile group for 2′‐OH protection of ribonucleosides: A major challenge for RNA synthesis. Chem. Eur. J. 14:9135‐9138.
   Lavergne, T., Martin, A., Debart, F., and Vasseur, J.‐J. 2008b. A whole base‐labile strategy for RNA synthesis with 2′‐O‐acetalester protections. Nucleic Acids Symp. Ser. 52:51‐52.
   Letsinger, R.L. and Lunsford, W.B. 1976. Synthesis of thymidine oligonucleotides by phosphite triester intermediates. J. Am. Chem. Soc. 98:3655‐3661.
   Lloyd, W., Reese, C.B., Song, Q., Vandersteen, A.M., Visintin, C., and Zhang, P.‐Z. 2000. Some observations relating to the use of 1‐aryl‐4‐alkoxypiperidin‐4‐yl groups for the protection of the 2′‐hydroxy functions in the chemical synthesis of oligoribonucleotides. J. Chem. Soc. Perkin Trans 1:165‐176.
   Lyttle, M.H., Wright, P.B., Sinha, N.D., Bain, J.D., and Chamberlin, A.R. 1991. New nucleoside phosphoramidites and coupling protocols for solid‐phase RNA synthesis. J. Org. Chem. 56:4608‐4615.
   Manoharan, M. 2004. RNA interference and chemically modified small interfering RNAs. Curr. Opin. Chem. Biol. 8:570‐579.
   Marshall, W.S. and Kaiser, R.J. 2004. Recent advances in the high‐speed solid phase synthesis of RNA. Curr. Opin. Chem. Biol. 8:222‐229.
   Matysiak, S. and Pfleiderer, W. 2001. Acetals as new 2′‐O‐protecting functions for the synthesis of oligoribonucleotides: Synthesis of monomeric building units and oligoribonucleotides. Helv. Chim. Acta 84:1066‐1085.
   Matysiak, S., Fitznar, H.–P., Schnell, R., and Pfleiderer, W. 1998. Acetals as new 2′‐O‐protecting functions for the synthesis of oligoribonucleotides: Synthesis of uridine building blocks and evaluation of their relative acid stability. Helv. Chim. Acta 81:1545‐1566.
   McBride, L.J. and Caruthers, M.H. 1983. An investigation of several deoxynucleoside phosphoramidites useful for synthesizing deoxyoligonucleotides. Tetrahedron Lett. 24:245‐248.
   McBride, L.J., Kierzek, R., Beaucage, S.L., and Caruthers, M.H. 1986. Amidine protecting groups for oligonucleotide synthesis. J. Am. Chem. Soc. 108:2040‐2048.
   Milecki, J., Dembek, P., Antkowiak, W.Z., Gdaniec, Z., Mielewczyk, S., and Adamiak, R.W. 1989. On the application of t‐butyldimethylsilyl group in chemical RNA synthesis. Part I. 31P NMR study of 2′‐O‐t‐BDMSi group migration during nucleoside 3′‐OH phosphorylation and phosphitylation reactions. Nucleosides Nucleotides 8:463‐474.
   Morgan, M.A., Kazakov, S.A., and Hecht, S.M. 1995. Phosphoryl migration during the chemical synthesis of RNA. Nucleic Acids Res. 23:3949‐3953.
   Müller, S., Wolf, J., and Ivanov, S.A. 2004. Current strategies for the synthesis of RNA. Curr. Org. Synth. 1:293‐307.
   Ogilvie, K.K. 1973. The tert‐butyldimethylsilyl group as a protecting group in deoxynucleosides. Can. J. Chem. 51:3799‐3807.
   Ogilvie, K.K. and Theriault, N.Y. 1979. The synthesis of oligoribonucleotides V. The stepwise synthesis of the 3′‐terminal heptanucleotide sequence of tRNAfMet from E. coli. Can. J. Chem. 57:3140‐3144.
   Ogilvie, K.K., Sadana, K.L., Thompson, E.A., Quilliam, M.A., and Westmore, J.B. 1974. The use of silyl groups in protecting the hydroxyl function of ribonucleosides. Tetrahedron Lett. 1:2861‐2863.
   Ogilvie, K.K., Theriault, N., and Sadana, K.L. 1977. Synthesis of oligoribonucleotides. J. Am. Chem. Soc. 99:7741‐7743.
   Ogilvie, K.K., Beaucage, S.L., Schifman, A.L., Theriault, N.Y., and Sadana, K.L. 1978. The synthesis of oligoribonucleotides. II. The use of silyl protecting groups in nucleoside and nucleotide chemistry.VII. Can. J. Chem. 56:2768‐2780.
   Ogilvie, K.K., Nemer, M.J., Hakimelahi, G.H., Proba, Z.A., and Lucas, M. 1982. N‐Levulination of nucleosides. Tetrahedron Lett. 23:2615‐2618.
   Ogilvie, K.K., Usman, N., Nicoghosian, K., and Cedergren, R.J. 1988. Total chemical synthesis of a 77‐nucleotide‐long RNA sequence having methionine‐acceptance activity. Proc. Natl. Acad. Sci. U.S.A. 85:5764‐5768.
   Ohgi, T., Masutomi, Y., Ishiyama, K., Kitagawa, H., Shiba, Y., and Yano, J. 2005. A new RNA synthetic method with 2′‐O‐(2‐cyanoethoxymethyl) protecting group. Org. Lett. 7:3477‐3480.
   Ohtsuka, E., Tanaka, S., and Ikehara, M. 1974. Studies on transfer ribonucleic acids and related compounds. IX Ribooligonucleotide synthesis using a photosensitive o‐nitrobenzyl protection at the 2′‐hydroxyl group. Nucleic Acids Res. 1:1351‐1357.
   Ohtsuka, E., Tanaka, S., and Ikehara, M. 1978. Studies on transfer ribonucleic acids and related compounds. 23. Synthesis of a heptanucleotide corresponding to a eukaryotic initiator tRNA loop sequence. J. Am. Chem. Soc. 100:8210‐8213.
   Owen, G.R. and Reese, C.B. 1970. A convenient preparation of tetrahydro‐4H‐pyran‐4‐one. J. Chem. Soc. (C): 2401‐2403.
   Ozola, V., Reese, C.B., and Song, Q. 1996. Use of ammonium aryl H‐phosphonates in the preparation of nucleoside H‐phosphonate building blocks. Tetrahedron Lett. 37:8621‐8624.
   Parey, N., Baraguey, C., Vasseur, J.‐J., and Debart, F. 2006. First evaluation of acyloxymethyl or acylthiomethyl groups as biolabile 2′‐O‐protection of RNA. Org. Lett. 8:3869‐3872.
   Pitsch, S., Weiss, P.A., Jenny, L., Stutz, A., and Wu, X. 2001. Reliable chemical synthesis of oligoribonucleotides (RNA) with 2′‐O‐[(triisopropylsilyl)oxy]methyl (2′‐O‐tom)‐protected phosphoramidites. Helv. Chim. Acta 84:3773‐3795.
   Pon, R.T. and Yu, S. 1997. Hydroquinone‐O,O′‐diacetic acid (‘Q‐linker’) as a replacement for succinyl and oxalyl linker arms in solid phase oligonucleotide synthesis. Nucleic Acids Res. 25:3629‐3635.
   Pon, R.T., Yu, S., Prabhavalkar, T., Mishra, T., Kulkarni, B., and Sanghvi, Y.S. 2005. Large‐scale synthesis of “Cpep” RNA monomers and their application in automated RNA synthesis. Nucleosides Nucleotides & Nucleic Acids 24:777‐781.
   Porcher, S. and Pitsch, S. 2005. Synthesis of 2′‐O‐[(triisopropylsilyl)oxy]methyl (=tom)‐protected ribonucleoside phosphoramidites containing various nucleobase analogues. Helv. Chim. Acta 88:2683‐2704.
   Rao, M.V. and Macfarlane, K. 1995. Improvements to the chemical synthesis of biologically‐active RNA using 2′‐O‐Fpmp chemistry. Nucleosides Nucleotides 14:911‐915.
   Rao, M.V., Reese, C.B., Schehlmann, V., and Yu, P.S. 1993. Use of the 1‐(2‐fluorophenyl)‐4‐methoxypiperidin‐4‐yl (Fpmp) protecting group in the solid phase synthesis of oligo‐ and poly‐ribonucleotides. J. Chem. Soc. Perkin Trans. 1:43‐55.
   Reese, C.B. 1978. The chemical synthesis of oligo‐ and poly‐nucleotides by the phosphotriester approach. Tetrahedron 34:3143‐3179.
   Reese, C.B. 1989. The chemical synthesis of oligo‐ and poly‐ribonucleotides. In Nucleic Acids and Molecular Biology, Vol. 3 (F. Eckstein and D.M.J. Lilley, eds.), pp. 164‐181, Springer, Berlin.
   Reese, C.B. 2002. The chemical synthesis of oligo‐ and poly‐nucleotides: A personal commentary. Tetrahedron 58:8893‐8920.
   Reese, C.B. 2005. Oligo‐ and poly‐nucleotides: 50 years of chemical synthesis. Org. Biomol. Chem. 3:3851‐3868.
   Reese, C.B. and Song, Q., 1999. The H‐phosphonate approach to the solution phase synthesis of linear and cyclic oligoribonucleotides. Nucleic Acids Res. 27:963‐971.
   Reese, C.B and Thompson, E.A. 1988. A new synthesis of 1‐arylpiperidin‐4‐ols. J. Chem. Soc. Perkin Trans. 1:2881‐2885.
   Rozners, E., Westman, E., and Strömberg, R. 1994. Evaluation of 2′‐hydroxyl protection in RNA‐synthesis using the H‐Phosphonate approach. Nucleic Acids Res. 22:94‐99.
   Sandström, A., Kwiatkowski, M., and Chattopadhyaya, J. 1985. Chemical synthesis of a pentaribonucleoside tetraphosphate constituting the 3′‐acceptor stem sequence of E. coli tRNAIle using 2′‐O‐(3‐methoxy‐1,5‐dicarbomethoxypentan‐3‐yl)‐ribonucleoside building blocks. Application of a new achiral and acid‐labile 2‐hydroxyl protecting group in tRNA synthesis. Acta Chem. Scand. B 39:273‐290.
   Saneyoshi, H., Seio, K., and Sekine, M. 2005. A general method for the synthesis of 2′‐O‐cyanoethylated oligoribonucleotides having promising hybridization affinity for DNA and RNA and enhanced nuclease resistance. J. Org. Chem. 70:10453‐10460.
   Saneyoshi, H., Ando, K., Seio, K., and Sekine, M. 2007. Chemical synthesis of RNA via 2′‐O‐cyanoethylated intermediates. Tetrahedron 63:11195‐11203.
   Scaringe, S.A. 2001. RNA oligonucleotide synthesis via 5′‐silyl‐2′‐orthoester chemistry. Methods 23:206‐217.
   Scaringe, S.A., Francklyn, C., and Usman, N. 1990. Chemical synthesis of biologically active oligoribonucleotides using β‐cyanoethyl protected ribonucleoside phosphoramidites. Nucleic Acids Res. 18:5433‐5441.
   Scaringe, S.A., Wincott, F.E., and Caruthers, M.H. 1998. Novel RNA synthesis method using 5′‐O‐silyl‐2′‐O‐orthoester protecting groups. J. Am. Chem. Soc. 120:11820‐11821.
   Schwartz, M.E., Breaker, R.R., Asteriadis, G.T., deBear, J.S., and Gough, G.R. 1992. Rapid synthesis of oligoribonucleotides using 2′‐O‐(o‐nitrobenzyloxymethyl)‐protected monomers. Bioorg. Med. Chem. Lett. 2:1019‐1024.
   Semenyuk, A., Földesi, A., Johansson, T., Estmer‐Nilsson, C., Blomgren, P., Brännvall, M., Kirsebom, L.A., and Kwiatkowski, M. 2006. Synthesis of RNA using 2′‐O‐DTM protection. J. Am. Chem. Soc. 128:12356‐12357.
   Shiba, Y., Masuda, H., Watanabe, N., Ego, T., Takagaki, K., Ishiyama, K., Ohgi, T., and Yano, J. 2007. Chemical synthesis of a very long oligoribonucleotide with 2‐cyanomethoxymethyl (CEM) as the 2′‐O‐protecting group: structural identification and biological activity of a synthetic 110mer precursor‐microRNA candidate. Nucleic Acids Res. 35:3287‐3296.
   Somoza, Á. 2008. Protecting groups for RNA synthesis: An increasing need for selective methods. Chem. Soc. Rev. 37:2668‐2675.
   Sproat, B.S. 1993. Synthesis of 2′‐O‐alkyloligoribonucleotides. In Methods in Molecular Biology, Vol 20: Protocols for Oligonucleotides and Analogs (S. Agrawal, ed.) pp.115‐141. Humana Press, Totowa, N.J.
   Sproat, B.S. 2005. RNA synthesis using 2′‐O‐(tert‐butyldimethylsilyl) protection. In Methods in Molecular Biology, Vol 288: Oligonucleotide Synthesis: Methods and Applications (P. Herdewijn, ed.) pp.17‐31. Humana Press, Totowa, N.J.
   Sproat, B.S., Colonna, F., Mullah, B., Tsou, D., Andrus, A., Hampel, A., and Vinayak, R. 1995. An efficient method for the isolation and purification of oligoribonucleotides. Nucleosides Nucleotides 14:255‐273.
   Tanaka, S., Hirakawa, T., Oishi, K., Hayakawa, Y., and Kitamura, M. 2007. A new synthetic route to oligoribonucleotides based on CpRu‐catalyzed deallylation. Tetrahedron Lett. 48:7320‐7322.
   Umemoto, T. and Wada, T. 2004. Oligoribonucleotide synthesis by the use of 1‐(2‐cyanoethoxy)ethyl (CEE) as a 2′‐hydroxy protecting group. Tetrahedron Lett. 45:9529‐9531.
   Usman, N., Ogilvie, K., Jiang, M.Y., and Cedergren, R. 1987. Automated chemical synthesis of long oligoribonucleotides using 2′‐O‐silylated ribonucleoside 3′‐O‐phosphoramidites on a controlled‐pore glass support: Synthesis of a 43‐nucleotide sequence similar to the 3′‐half molecule of an Escherichia coli formylmethionine tRNA. J. Am. Chem. Soc. 109:7845‐7854.
   van Boom, J.H. and Burgers, P.M.J. 1976. Use of levulinic acid in the protection of oligonucleotides via the modified phosphotriester method: Synthesis of the decaribonucleotide UAUAUAUAUA. Tetrahedron Lett. 4875‐4878.
   Vargeese, C., Carter, J., Yegge, J., Krivjansky, S., Settle, A., Kropp, E., Peterson, K., and Pieken, W. 1998. Efficient activation of nucleoside phosphoramidites with 4,5‐dicyanoimidazole during oligonucleotide synthesis. Nucleic Acids Res. 26:1046‐1050.
   Wada, T., Tobe, M., Nagayama, T., Furusawa, K., and Sekine, M. 1993. New strategies for oligonucleotide synthesis by use of 2‐trimethylsilylethyl and 2‐trimethylsilylethoxymethyl as the phosphate and 2‐hydroxyl protecting groups, respectively. Nucleic Acids Symp. Ser. 29:9‐10.
   Wada, T., Tobe, M., Nagayama, T., Furusawa, K., and Sekine, M. 1995. Regioselective protection of the 2‐hydroxyl group of N‐acyl‐3′,5′‐O‐di(t‐butyl)silanediylnucleoside derivatives by use of t‐BuMgCl and 2‐(trimethylsilyl)ethoxymethyl chloride. Tetrahedron Lett. 36:1683‐1684.
   Westman, E. and Strömberg, R. 1994. Removal of t‐butyldimethylsilyl protection in RNA‐synthesis. Triethylamine trihydrofluoride (TEA, 3HF) is a more reliable alternative to tetrabutylammonium fluoride (TBAF). Nucleic Acids Res. 22:2430‐2431.
   Wincott, F.E. and Usman, N. 1994. 2′‐(Trimethylsilyl)ethoxymethyl protection of the 2′‐hydroxyl group in oligoribonucleotide synthesis. Tetrahedron Lett. 35:6827‐6830.
   Wincott, F., DiRenzo, A., Shaffer, C., Grimm, S., Tracz, D., Workman, C., Sweedler, D., Gonzalez, C., Scaringe, S., and Usman, N. 1995. Synthesis, deprotection, analysis and purification of RNA and ribozymes. Nucleic Acids Res. 23:2677‐2684.
   Yan, H. and Aguilar, A.L., 2007. Synthesis of 3′,5′‐cyclic diguanylic acid (c‐diGMP) using 1‐(4‐chlorophenyl)‐4‐ethoxypiperidin‐4‐yl as a protecting group for the 2′‐hydroxy functions of ribonucleosides. Nucleosides Nucleotides Nucleic Acids 26:189‐204.
   Zhou, C., Honcharenko, D., and Chattopadhyaya, J. 2007a. 2‐(4‐Tolysulfonyl)ethoxymethyl (TEM) – a new 2′‐OH protecting group for solid‐supported RNA synthesis. Org. Biomol. Chem. 5:333‐343.
   Zhou, C., Pathmasiri, W., Honcharenko, D., Chatterjee, S., Barman, J., and Chattopadhyaya, J. 2007b. High‐quality oligo‐RNA synthesis using the new 2′‐O‐TEM protecting group by selectively quenching the addition of p‐tolyl vinyl sulphone to exocyclic amino functions. Can. J. Chem. 85:293‐301.
GO TO THE FULL PROTOCOL:
PDF or HTML at Wiley Online Library