Synthesis of selenium-derivatized cytidine and oligonucleotides for X-ray crystallography using MAD.

Synthesis of the novel 2'-Se-cytidine phosphoramidite was achieved via transformation of the uridine analogue to the cytidine derivative in high yield. This 2'-Se-cytidine phosphoramidite was used to synthesize selenium-derivatized DNA and RNA oligonucleotides for X-ray crystallography using MAD. The nucleotide coupling yield using this novel phosphoramidite was over 99% when 5-benzylmercaptotetrazole (5-BMT) was used as the coupling reagent.

Selenium derivatization and crystallization of DNA and RNA oligonucleotides for X-ray crystallography using multiple anomalous dispersion.

We report here the solid phase synthesis of RNA and DNA oligonucleotides containing the 2'-selenium functionality for X-ray crystallography using multiwavelength anomalous dispersion. We have synthesized the novel 2'-methylseleno cytidine phosphoramidite and improved the accessibility of the 2'-methylseleno uridine phosphoramidite for the synthesis of many selenium-derivatized DNAs and RNAs in large scales. The yields of coupling these Se-nucleoside phosphoramidites into DNA or RNA oligonucleotides were over 99% when 5-(benzylmercapto)-1H-tetrazole was used as the coupling reagent.