- Selective removal of the 2′- and 3′-0-acyl groups from 2′,3′,5′-tri-O-acylribonucleoside derivatives with lithium trifluoroethoxide
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Selective cleavage of O2′ and O3′ ester groups from ribonucleoside derivatives has been accomplished with Dowex 1 × 2 (CF 3CH2O-) in 2,2,2-trifluoroethanol (TFE) or lithium trifluoroethoxide/TFE. Deacylations with Li+ -OCH2CF3/TFE proceed at ambient temperature (or with mild heating) to give the 5′-O-acyl derivatives in superior yields and higher purity than prior approaches for selective O2′ and O3′ ester deprotection.
- Nowak, Ireneusz,Jones, Carl T.,Robins, Morris J.
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p. 3077 - 3081
(2007/10/03)
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- REMOVAL OF SILYL PROTECTING GROUPS FROM HYDROXYL FUNCTIONS WITH AMMONIUM FLUORIDE IN METHANOL
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Treatment of silyl ethers with excess ammonium fluoride in methanol at 60 deg C effected cleavage to alcohols within 5 hours.Deprotection at ambient temperature required 1-2 days.NH4F/MeOH is an economical alternative to TBAF/THF.
- Zhang, Weijian,Robins, Morris J.
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p. 1177 - 1180
(2007/10/02)
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- Molecular conformation of 2'-deoxy-3',5'-di-O-acetyl adenosine. Crystal structure and high resolution proton nuclear magnetic resonance investigations
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2'-Deoxy-3',5'-di-O-acetyl adenosine crystallizes in the orthorombic space group P212121, and the cell dimensions are a = 7.768(1) Angstroem, b = 12.890(1) Angstroem, c = 15.495(1) Angstroem; Z = 4 molecules per cell.Least-squares refinement converged at R = 0.054 for 1752 observed reflections.The adenine bases are linked via N6-H...N1 and N6-H...N7 hydrogen bonds, in such a way that infinite one-dimensional chains are formed.Comments are made on the fact that this structure is entirely different from the parallel dimer that was found for 3',5'-di-O-acetyl thymidine.Furthermore, the conformational preferences of the title compound in aqueous solution have been determined with 300- and 500-MHz 1H nmr.It is found that the X-ray structure and the solution conformation are essentially similar, except fot the C4'-C5' conformation, that isγ- in the solid state, and predominantly γ+ in solution.
- Koole, Leo H.,Buck, Henk M.,Kanters, Jan A.,Schouten, Arie
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p. 326 - 331
(2007/10/02)
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