DNA Phosphoramidites for Oligonucleotide Synthesis

　The phosphoramidite method is standard for oligonucleotide synthesis.^1,2) In this method, one nucleotide addition is conducted by a synthetic cycle with the following three steps: i) coupling of a phosphoramidite and an oligonucleotide at the 5’-OH of the terminal nucleoside with an activation reagent like 1H-tetrazole and capping of the unreacted hydroxy group; ii) oxidation or sulfurization of the phosphite moiety; iii) deprotection of the DMT group. This cycle is performed by an automated synthesizer and oligonucleotides can be prepared easily and quickly in this system.
　DNA phosphoramidites 1, 2, 3 and 4 are applicable for the synthesis of oligonucleotides including DNAs and utilized in the preparation of gapmer antisense oligonucleotide drugs containing DNA sequences such as mipomersen. The DNA sequence in the gapmer is an important part for the degradation of target RNAs catalyzed by RNase H to prevent gene expression.³⁾

References

• 1) Deoxynucleoside phosphoramidites-a new class of key intermediates for deoxypolynucleotide synthesis
• S. L. Beaucage, M. H. Caruthers, Tetrahedron Lett. 1981, 22, 1859.
• 2) Synthesis of DNA/RNA and their analogs via phosphoramidite and H-phosphonate chemistries
• S. Roy, M. H. Caruthers, Molecules 2013, 18, 14268.
• 3) Clinical pharmacological properties of mipomersen (Kynamro), a second generation antisense inhibitor of apolipoprotein B
• S. T. Crooke, R. S. Geary, Br. J. Clin. Pharmacol. 2013, 76, 269.

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