Kore Anilkumar R, Parmar Gaurang, Reddy Srinu
Ambion, Inc., Bioorganic Chemistry Division, Austin, Texas 78744, USA.
Nucleosides Nucleotides Nucleic Acids. 2006 Mar;25(3):307-14. doi: 10.1080/15257770500544529.
An improved strategy for the selective synthesis of 2'-O-methyl and 3'-O-methyl guanosine from 2-aminoadenosine is reported by using the catalyst stannous chloride. The regioselectivity of the 2' and 3'-O-alkylation was achieved by optimizing the addition, timing, and concentration of the catalysts and diazomethane during the methylation reaction. An efficient and selective alkylation at 2'-OH of 2-aminoadenosine was achieved by mixing a stoichiometric amount of stannous chloride at room temperature in DME The reaction mixture was stirred at 50 degrees C for 1 min and immediately followed by addition of diazomethane. The resulting 2'-O-methyl 2-aminoadenosine was treated with the enzyme adenosine deaminase, which resulted in an efficient conversion to the desired 2'-O-methylguanosine (98% yield). The product was isolated by crystallization. In contrast, the methylation at 3'-OH of 2-aminoadenosine was achieved by mixing a stoichiometric amount of stannous chloride in DMF and stirring at 50 degrees C for 15 min, followed by addition of diazomethane. The resulting mixture containing 3'-O-methyl-2-aminoadenosine in 90% yield and 2'-O-methyl-2-aminoadenosine in 10% yield was treated with the enzyme adenosine deaminase, which preferentially deaminated only 3'-O-methyl-2-aminoadenosine, resulting in the production of 3'-O-methylguanosine in 88% yield. Due to the extremely low solubility 3'-O-methylguanosine, the compound precipitated and was isolated by centrifugation. This synthetic route obviates the chromatographic purification. Selective monomethylation is achieved by using the unprotected ribonucleoside. As a result, the method described herein represents a significant improvement over the current synthetic approach by providing superior product yield and economy, a much more facile purification of 2',3'-O-methylated isomers, and eliminating the need for protected ribonucleosides reagents.
报道了一种使用氯化亚锡从2-氨基腺苷选择性合成2'-O-甲基和3'-O-甲基鸟苷的改进策略。通过优化甲基化反应过程中催化剂和重氮甲烷的添加量、添加时间和浓度，实现了2'和3'-O-烷基化的区域选择性。在室温下于二甲醚中混合化学计量的氯化亚锡，可实现2-氨基腺苷在2'-OH处的高效选择性烷基化。将反应混合物在50℃搅拌1分钟，然后立即加入重氮甲烷。所得的2'-O-甲基-2-氨基腺苷用腺苷脱氨酶处理，可高效转化为所需的2'-O-甲基鸟苷（产率98%）。产物通过结晶分离。相比之下，2-氨基腺苷在3'-OH处的甲基化是通过在N,N-二甲基甲酰胺中混合化学计量的氯化亚锡并在50℃搅拌15分钟，然后加入重氮甲烷来实现的。所得混合物中3'-O-甲基-2-氨基腺苷的产率为90%，2'-O-甲基-2-氨基腺苷的产率为10%，用腺苷脱氨酶处理，该酶仅优先脱氨3'-O-甲基-2-氨基腺苷，从而以88%的产率生成3'-O-甲基鸟苷。由于3'-O-甲基鸟苷的溶解度极低，该化合物沉淀并通过离心分离。这种合成路线避免了色谱纯化。使用未保护的核糖核苷实现了选择性单甲基化。因此，本文所述方法通过提供更高的产物产率和经济性、更简便地纯化2',3'-O-甲基化异构体以及无需使用保护的核糖核苷试剂，代表了对当前合成方法的显著改进。
