2002 nucleic acids

nucleic acidsU 0700

08 - 251Synthesis of Selenium-Derivatized Nucleosides and Oligonucleotidesfor X-Ray Crystallography. — Introduction of selenium into nucleosideand oligonucleotide analogues as anomalous scatterer enables Multiwave-length Anomalous Dispersion (MAD) phase determination in nucleotide X-raycrystallography. Instead of the conventional approach, a two-phase system(H2O/toluene) is applied to incorporate selenium using a phase-transfer catalyst.The 5’-hydroxy groups of partially protected nucleosides, e.g. (I) and (VII),are activated for nucleophilic substitution with the leaving groups bromide,tosyl, or mesyl. The reactions assisted by the phase-transfer catalyst are fast,easy to workup, and give excellent yields. Oligonucleotides containing seleniumare prepared by standard phosphoramidite procedures. — (CARRASCO,NICOLAS; GINSBURG, DOV; DU, QUAN; HUANG, ZHEN; Nucleosides,Nucleotides Nucleic Acids 20 (2001) 9, 1723-1734; Dep. Chem., Brooklyn Coll.,City Univ. N. Y., Brooklyn, NY 11210, USA; EN)

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