Synthesis of 4′-Selenoribonucleosides, the Building Blocks of 4′-SelenoRNA, Using a Hypervalent Iodine

Herein is described a detailed protocol for the synthesis of 4′-selenoribonucleoside derivatives that involves the use of a hypervalent iodine species. These derivatives are versatile units for the preparation of 4′-selenoRNA. Large-scale synthesis of a 4-selenosugar starting from D-ribose is achieved in eight steps, including a final chromatographic purification. The resulting 4-selenosugar is then subjected to the one-pot Pummerer-like reaction using hypervalent iodine in the presence of silylated nucleobases. The reaction with silylated uracil affords the desired 4′-selenouridine derivatives with excellent β-selectivity and in good yield. Conversely, when purine nucleobases are used in the Pummerer-like reaction, N7 4′-selenoribonucleoside isomers are obtained alongside the desired N9 isomers. However, the undesired N7 isomers can be converted to the desired N9 ones under acidic conditions. © 2017 by John Wiley & Sons, Inc.