Benzimidazolium Triflate as an Efficient Promoter for Nucleotide Synthesis via the Phosphoramidite Method.
Benzimidazolium Triflate as an Efficient Promoter for Nucleotide Synthesis via the Phosphoramidite Method.
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苯并咪唑鎓三氟甲磺酸盐作为亚磷酰胺法核苷酸合成的有效促进剂。
DOI：
10.1002/chin.199716251
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
R. Noyori
中科院分区：
文献类型：
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作者：
Y. Hayakawa;M. Kataoka;R. Noyori
核苷亚磷酰胺和核苷的缩合是寡核苷酸合成中的重要步骤。1该反应通常需要唑类促进剂，如1H-四唑、2 5-（对硝基苯基）-1H-四唑（NPT）、3和5-（乙硫基）-1H-四唑。4然而，这些试剂中没有一种对核苷亚磷酰胺如芳基化脱氧核糖核苷N，N-二异丙基亚磷酰胺或磷吗啉和空间拥挤的核糖核苷N，N-二异丙基亚磷酰胺足够有效。这些酰胺的反应性的缺乏阻止了具有作为反义分子有吸引力的修饰的主链的一些寡核苷酸的制备。因此，非常需要发明具有有效促进能力的新试剂。我们在此公开了苯并咪唑鎓三氟甲磺酸盐（1）6完全满足这样的要求（方案1）。通过在室温下在二氯甲烷中混合等摩尔量的苯并咪唑和三氟甲磺酸定量获得试剂1，mp 188 - 190 ℃。该试剂可在环境温度和大气下储存而不分解。该盐在乙腈中具有良好的溶解性，约为100%。0.4 mol/L，与1H-四唑（约. 0.5 mol/L），高于NPT（约. 0.1 mol/L）。3三氟甲磺酸酯1是一种反应性极强的启动子，通常在25 ℃下在1分钟内完成核苷亚磷酰胺和核苷的缩合，甚至与通常反应性弱的亚酰胺如芳基化脱氧核糖核苷3′-亚磷吗啉或空间拥挤的核糖核苷N，N-二异丙基亚磷酰胺。表1列出了通过亚酰胺2 r6和10 r12与核苷13 r15缩合，然后叔丁基过氧化氢（TBHP）氧化制备磷酸酯的几个实例。[7] 1的高反应活性允许亚磷酰胺与吸电子取代基如邻氯苯基快速缩合。8，9也可以使用空间拥挤的核糖核苷亚磷酰胺。使用相对于核苷（1当量）略微过量的亚磷酰胺和促进剂（各1.2当量）以产生合理的反应速率。苯并咪唑鎓试剂以化学选择性的方式活化亚磷酰胺，而没有明显的劣化，以实现具有（烯丙氧基）羰基、11叔丁基二甲基甲硅烷基或甚至单
The condensation of a nucleoside phosphoramidite and a nucleoside is an essential step in oligonucleotide synthesis. 1 This reaction usually requires an azole promoter such as 1H-tetrazole, 2 5-(p-nitrophenyl)-1H-tetrazole (NPT), 3 and 5-(ethylthio)-1H-tetrazole. 4 None of these reagents, however, is sufficiently effective for nucleoside phosphoramidites such as arylated deoxyribonucleoside N, N-diisopropylphosphoramidites or phosphoromorpholidites and sterically crowded ribonucleoside N, N-diisopropylphosphoramidites. The lack of reactivity of these amidites prevents the preparation of some oligonucleotides with modified backbones that are attractive as antisense molecules. 5 Thus, the invention of new reagents with a potent promotion ability is highly desirable. We disclose here that benzimidazolium triflate (1) 6 perfectly meets such a requirement (Scheme 1). The reagent 1, mp 188r190 C, was quantitatively obtained by mixing benzimidazole and trifluoromethanesulfonic acid in equimolar amounts in dichloromethane at room temperature. This reagent can be stored at ambient temperature under atmosphere without decomposition. This salt has good solubility in acetonitrile, ca. 0.4 mol/L, which is comparable to that of 1H-tetrazole (ca. 0.5 mol/L) and higher than that of NPT (ca. 0.1 mol/L). 3 The triflate 1 is an extremely reactive promoter, generally accomplishing the condensation of a nucleoside phosphoramidite and a nucleoside within 1 min at 25 C, even with normally weakly reactive amidites such as arylated deoxyribonucleoside 3′-phosphoromorpholidites or sterically crowded ribonucleoside N, N-diisopropylphosphoramidites. Table 1 lists several examples of the preparation of phosphates via the condensation of the amidites, 2r6 and 10r12, and the nucleosides, 13r15, followed by tert-butyl hydroperoxide (TBHP) oxidation. 7 The high reactivity of 1 allowed rapid condensation of phosphoramidites with an electron-withdrawing substituent such as o-chlorophenyl. 8, 9 The sterically crowded ribonucleoside phosphoramidites could also be used. A slight excess of the phosphoramidite and the promoter (1.2 equiv each) to the nucleoside (1 equiv) was employed to produce a reasonable rate of reaction. 10 The benzimidazolium reagent activated the phosphoramidite in a chemoselective manner without noticeable deterioration to effect the reaction of the substrates having an (allyloxy) carbonyl, 11 tert-butyldimethylsilyl, or even mono-