Two‐Step, One‐Pot Synthesis of Inosine, Guanosine, and 2′‐Deoxyguanosine O6‐Ethers via Intermediate O6‐(Benzotriazol‐1‐yl) Derivatives

Hari Prasad Kokatla1, Mahesh K. Lakshman1

1 The City College and The City University of New York, New York City, New York
Publication Name:  Current Protocols in Nucleic Acid Chemistry
Unit Number:  Unit 1.26
DOI:  10.1002/0471142700.nc0126s49
Online Posting Date:  June, 2012
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A simple method for the etherification at the O6‐position of silyl‐protected inosine, guanosine, and 2′‐deoxyguanosine is described. Typically, a THF solution of the silylated nucleoside is treated with 1H‐benzotriazol‐1‐yloxy‐tris(dimethylamino)phosphonium hexafluorophosphate (BOP) and Cs2CO3 under a nitrogen atmosphere. Conversion to the O6‐(benzotriazol‐1‐yl) ethers occurs within about 10 min for inosine, and within about 60 min for guanosine and 2′‐deoxyguanosine. Then, for reaction with alcohols, the reaction mixture is evaporated and the O6‐(benzotriazol‐1‐yl) ether is treated with Cs2CO3 and an appropriate alcohol, at room temperature. On the other hand, for reaction with phenols, Cs2CO3 and the appropriate phenol are added to the reaction mixture without evaporation, and the reaction is carried out at 70°C. Subsequently, workup, isolation, and purification lead to the requisite O6‐alkyl or O6‐aryl ethers in good to excellent yields. Curr. Protoc. Nucleic Acid Chem. 49:1.26.1‐1.26.16. © 2012 by John Wiley & Sons, Inc.

Keywords: inosine; guanosine; 2′‐deoxyguanosine; BOP; reactive nucleosides; ethers; benzotriazolyl

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Table of Contents

  • Commentary
  • Literature Cited
  • Figures
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Basic Protocol 1:

  • Inosine ( S.1), 99% (Acros)
  • Anhydrous pyridine, distilled from KOH (stored over KOH)
  • N,N‐Dimethylformamide (DMF), anhydrous (Aldrich)
  • Imidazole, 99% pure (Sigma)
  • tert‐Butyldimethylsilyl chloride (TBDMS‐Cl), 98% pure (Acros)
  • Hexanes, ACS grade (Fisher Scientific)
  • Dichloromethane (CH 2Cl 2), ACS grade (Fisher Scientific)
  • Sodium sulfate (Na 2SO 4), anhydrous, 99% pure (Spectrum)
  • 200‐ to 300‐mesh silica gel (Natland,
  • Ethyl acetate (EtOAc), HPLC grade (Fisher Scientific)
  • Guanosine ( S.5), 98% (Lancaster Synthesis)
  • 2′‐Deoxyguanosine ( S.9), 98% (Transgenomic, http://www/
  • 1H‐Benzotriazol‐1‐yloxy‐tris(dimethylamino)phosphonium hexafluorophosphate (BOP), ≥98% pure (Chem‐Impex,
  • Tetrahydrofuran (THF): distilled over lithium aluminum hydride (LiAlH 4) and then distilled over sodium just prior to use
  • Cesium carbonate (Cs 2CO 3), 99% pure (Aldrich)
  • Nitrogen gas and balloons
  • Alcohols and phenols for reaction with S.2, S.6, and S.10:
    • Methanol (for S.4a, S.8a, and S.12a)
    • Allyl alcohol (for S.4b)
    • Propargyl alcohol (for S.4c)
    • Isopropyl alcohol (for S.4d)
    • Ethylene glycol (for S.4e)
    • p‐Nitrophenol (for S.4f)
    • p‐Methoxyphenol (for S.8b)
    • Phenol (for S.12b)
  • 50‐ and 100‐mL round‐bottom flasks
  • Rotary evaporator equipped with a water aspirator
  • Magnetic stirrer and stir bars
  • Büchner funnel and appropriate filter flask
  • Water aspirator
  • Glass funnel, plugged with cotton
  • Oil pump for vacuum drying
  • TLC plates: 200‐µm aluminum foil‐backed silica gel plates with fluorescent indicator (for TLC analysis; Analtech)
  • Dual‐wavelength UV lamp (254 and 365 nm; for TLC analysis)
  • 70°C temperature‐controlled sand bath
  • 4‐mL clear glass vials with Teflon/rubber‐lined, closed‐top, screw caps (Wheaton) for conducting etherification reactions
  • 60‐ and 125‐mL separatory funnels
  • Fraction collector
  • Additional reagents and equipment for thin‐layer chromatography (TLC; appendix 3D) and silica gel column chromatography ( appendix 3E)
NOTE: Except where indicated above, all reagents were obtained from commercial sources and used without further purification.
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Literature Cited

Literature Cited
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