Nucleic Acid Related Compounds. 127. Selective N-Deacylation of N,O-Peracylated Nucleosides in Superheated Methanol1
摘要:
Solutions of peracylated adenosine, cytidine, and related nucleoside derivatives undergo selective N-deacylation upon heating at elevated temperatures (oil bath >= 105 degrees C) in methanol. An increase in the bulk of the N-acyl group has little effect on the rate of N-deacylation but increases the N/O selectivity ratio. Extended heating is required for N-deacylation with arylcarboxylic acid derivatives. Contamination with acidic or basic reagent residues is avoided.
Selective Removal of the 2‘- and 3‘-<i>O</i>-Acyl Groups from 2‘,3‘,5‘-Tri-<i>O</i>-acylribonucleoside Derivatives with Lithium Trifluoroethoxide<sup>1</sup>
作者:Ireneusz Nowak、Carl T. Jones、Morris J. Robins
DOI:10.1021/jo0600104
日期:2006.4.1
Selective cleavage of O2' and O3' ester groups from ribonucleoside derivatives has been accomplished with Dowex 1 x 2 (CF3CH2O-) 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.
Oligonucleotide Synthesis Involving Deprotection of Amidine-Type Protecting Groups for Nucleobases under Acidic Conditions
Amidine-type protecting groups, i.e., N,N-dimethylformamidine (dmf) and N,N-dibutylformamidine (dbf) groups, introduced Into nucleobases were rapidly removed under mild acidic conditions using imidazolium triflate (IMT) or 1-hydroxybenztriazole (HOBt). This new deprotection strategy allowed a 2'-O-methyl-RNA derivative bearing a base-labile group to be efficiently synthesized using a silyl-type linker. It was also found that our new method could be applied to the synthesis of an unmodified RNA oligomer.
Nucleic Acid Related Compounds. 127. Selective N-Deacylation of N,O-Peracylated Nucleosides in Superheated Methanol<sup>1</sup>
作者:Ireneusz Nowak、Martin Conda-Sheridan、Morris J. Robins
DOI:10.1021/jo051256w
日期:2005.9.1
Solutions of peracylated adenosine, cytidine, and related nucleoside derivatives undergo selective N-deacylation upon heating at elevated temperatures (oil bath >= 105 degrees C) in methanol. An increase in the bulk of the N-acyl group has little effect on the rate of N-deacylation but increases the N/O selectivity ratio. Extended heating is required for N-deacylation with arylcarboxylic acid derivatives. Contamination with acidic or basic reagent residues is avoided.
<i>N</i>-Oxides of Adenosine-Type Nucleosides Undergo Pyrimidine Ring Opening and Closure To Give 5-Amino-4-(1,2,4-oxadiazol-3-yl)imidazole Derivatives
作者:Ireneusz Nowak、John F. Cannon、Morris J. Robins
DOI:10.1021/ol061715v
日期:2006.9.1
Treatment of acylated adenosine N-oxides with carboxylic anhydrides and thiophenol resulted in pyrimidine ring opening followed by exocyclic ring closure. Ammonolysis gave 5-amino-4-(5-substituted-1,2,4-oxadiazol-3-yl)-1-(beta-d-ribofuranosyl)imidazole derivatives, whereas iodine in methanol selectively unmasked the 5-amino group. Related flexible nucleoside analogues can be prepared from adenine-type