In recent years, nucleic acid medicine, in which oligonucleotides are applied as pharmaceuticals, has been drawing attention. On the other hand, nucleic acid drugs have been considered to have low stability because nucleic acid drugs are degraded by enzymes in the human body before reaching the affected site. This is due to the fact that phosphate ester bonds, which are part of the structure, are easily cleaved by nucleases. Therefore, many nucleic acid drug designs have been reported in which the phosphate ester bond is converted to a thiophosphate bond (phosphorothioate)1) in order to improve the stability. Phosphorothioate nucleic acids are used in many antisense nucleic acid drugs because phosphorothioate nucleic acids have resistance to nucleases and also can be synthesized easily and inexpensively.
Beaucage reagent (Product No. B3125), bis(phenylacetyl)disulfide (Product No. B3623), xanthane hydride (Product No. X0001) and DDTT (Product No. D5920)2) are used as sulfur transfer reagents in the synthesis of phosphorothioate oligonucleotides by the phosphoramidite method. In particular, xanthane hydride and DDTT have the advantage that oxidizing substances, carbon disulfide and cyanamide are not produced as byproducts during the reaction. For DNA/RNA synthesizer, xanthane hydride solution is used, such as 0.02 M solution in acetonitrile/pyridine (9:1)3) or 0.20 M solution in pyridine.4) DDTT has a dmf-protected amino group compared with xanthane hydride, and is expected to be more stable than xanthane hydride in the solution state.
- 1) W. J. Stec, G. Zon, W. Egan, J. Am. Chem. Soc. 1984, 106, 6077.
- 2) A. P. Guzaev, Tetrahedron Lett. 2011, 52, 434.
- 3) J. Tang, Y. Han, J. X. Tang, Z. Zhang, Org. Proc. Res. Dev. 2000, 4, 194.
- 4) I. Cedillo, D. Chreng, E. Engle, L. Chen, A. K. McPherson, A. A. Rodriguez, Molecules 2017, 22, 1356.