- N -Glycosylation with sulfoxide donors for the synthesis of peptidonucleosides
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The synthesis of glycopyranosyl nucleosides modified in the sugar moiety has been less frequently explored, notably because of the lack of a reliable method to glycosylate pyrimidine bases. Herein we report a solution in the context of the synthesis of peptidonucleosides. They were obtained after glycosylation of different pyrimidine nucleobases with glucopyranosyl donors carrying an azide group at the C4 position. A methodological study involving different anomeric leaving groups (acetate, phenylsulfoxide and ortho-hexynylbenzoate) showed that a sulfoxide donor in combination with trimethylsilyl triflate as the promoter led to the best yields.
- Beau, Jean-Marie,Beretta, Margaux,Dr?ge, Thomas,Es-Sayed, Mazen,Nicolas, Lionel,Norsikian, Stéphanie,Rouchaud, Emilie,Vors, Jean-Pierre
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supporting information
p. 4285 - 4291
(2021/05/31)
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- Probing Synergistic Effects of DNA Methylation and 2′-β-Fluorination on i-Motif Stability
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The possible role of DNA i-motif structures in telomere biology and in the transcriptional regulation of oncogene promoter regions is supported by several recent studies. Herein we investigate the effect of four cytidine nucleosides (and combinations thereof) on i-motif structure and stability, namely 2′-deoxycytidine (dC), 2′-deoxy-5-methyl-cytidine (5-Me-dC), 2′-deoxy-2′-fluoro-arabinocytidine (2′F-araC), and 2′-deoxy-2′-fluoro-5-methyl-arabinocytidine (5-Me-2′F-araC). The base pair 5-Me-2′F-araC:2′F-araC produced i-motifs with a pH1/2 (“pKa”) value that closely matches physiological pH (7.34±0.3). NMR analysis of the most stable telomeric sequence (HJ-2) at pH 7.0 indicated that the structure is stabilized by hybrid 5-Me-dC:2′F-araC hemiprotonated base pairs and therefore highlights the significance of the interplay between base and sugar modifications on the stability of i-motif structures.
- Abou Assi, Hala,Lin, Yu Chen,Serrano, Israel,González, Carlos,Damha, Masad J.
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supporting information
p. 471 - 477
(2017/12/15)
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- 2′-O-aminoethyl oligoribonucleotides containing novel base analogues: Synthesis and triple-helix formation at pyrimidine/purine inversion sites
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The synthesis of a common sugar intermediate for the 2′-aminoethyl- ribonucleoside synthesis in 9 steps and an overall yield of 33 % starting from D-ribose is described. This intermediate was successfully used for the synthesis of the 2′-aminoethyl-ribonucleosides containing the bases thymine (t), 5-methylcytosine (c), 5-methyl-2-pyrimidinone (x), 2-aminopurine (ap) and guanine (g). These were subsequently transformed into the corresponding cyanoethyl phosphoramidite building blocks for oligonucleotide synthesis. 2′-Aminoethyl oligonucleotide 15-mers were prepared with a DNA synthesizer, and an optimized post-synthetic deprotection protocol has been developed which prevents cyanoethylation of the 2′-amino side chains during conventional ammonia deprotection. A series of fully modified, triplex forming 2′-aminoethyl oligoribonucleotides (2′AE-TFOs) were prepared in which x was designed to bind to CG inversion sites and ap as well as g to TA inversion sites on a double-helical DNA target. The affinity of x-CG base-triple formation in different sequence contexts was assessed by UV- and CD melting analysis. It was found that TFO 15-mers containing up to 5 x residues still form stable triplexes even in the case where all x residues are consecutively arranged in the TFO. The nearest neighbor properties of x have been probed and it was found that triplex stability decreases in the local sequence order -txt- > -txc- ? -cxc-. TFOs containing ap and g were found to bind to their DNA targets with TA inversion sites with less affinity and less selectivity compared to TFOs containing the corresponding deoxyribonucleosides, irrespective whether they were incorporated in TFOs with a DNA or a 2′-AE-RNA backbone. The obtained data suggest that guanine-TA or aminopurine-TA base-triple formation is strongly sensitive to TFO conformation and more efficient in TFOs with a DNA than an RNA backbone. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Buchini, Sabrina,Leumann, Christian J.
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p. 3152 - 3168
(2007/10/03)
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- SYNTHESIS OF N-(2-PHOSPHONYLMETHOXYETHYL) DERIVATIVES OF HETEROCYCLIC BASES
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The preparation of N-(2-phosphonylmethoxyethyl) derivatives of purine and pyrimidine bases, IV, as analogs of the antiviral 9-(2-phosphonylmethoxyethyl)adenine (PMEA,I), is described.The synthesis consists in alkylation of alkali metal salts of heterocyclic bases or their N- or O-substituted derivatives with diethyl 2-p-toluenesulfonyloxyethoxymethylphosphonate (IIa), 2-chloroethoxymethylphosphonate (IIb) or 2-bromoethoxymethylphosphonate (IIc).The obtained N-(2-diethoxyphosphonylmethoxyethyl) derivatives of heterocyclic bases (III) were treated with bromotrimethylsilane to give phosphonic acids IV.Compounds IV were prepared from pyrimidines (uracil, cytosine and their 5-methyl derivatives), purines (adenine and its N6- and C(2)-substituted derivatives, hypoxanthine, guanine, 6-hydrazinopurine and 6-methylthiopurine etc.) and their analogs (3-deazaadenine etc.).
- Holy, Antonin,Rosenberg, Ivan,Dvorakova, Hana
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p. 2190 - 2210
(2007/10/02)
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