(605b) New Insights into the Difficulties and Importance of Dichloroacetic Acid Removal Post Detritylation in the Solid Phase Oligonucleotides Synthesis Cycle

Therapeutic oligonucleotides have received significant attention across the pharmaceutical industry. Solid phase oligonucleotide synthesis (SPOS) is the main approach of manufacturing oligonucleotides. SPOS is well known to have high cost and large amount of organic waste [1]. Organic solvent used in post-reaction washing is the main contributor to SPOS waste generation. In this study, we have investigated the impact of washing in SPOS. The importance of washing away dichloroacetic acid (DCA) after dimethoxytrityl (DMT) group deprotection and before coupling with the next activated phosphoroamidite is well known. However, the binding of DCA to the resin and the growing oligonucleotide, and the limiting factors of DCA removal from the resin bed prior to coupling have not been studied on a fundamental level. We have measured the adsorption-desorption isotherms of DCA on the solid phase at different progress of oligo synthesis. The longer the oligonucleotide strand on solid phase, the more DCA can be adsorbed on solid phase at certain concentrations of DCA in the liquid phase. Longer oligonucleotide strand also leads to more adsorption-desorption hysteresis, which significantly impacts the amount of solvent required for washing away DCA prior to coupling. Based on these findings, we have engineered washing strategies that yields high purity and high yield and significantly enhancing the sustainability of the oligonucleotide synthesis process.

References

[1] B. I. Andrews, F. D. Antia, S. B. Brueggemeier, L. J. Diorazio, S. G. Koenig, M. E. Kopach, H. Lee, M. Olbrich and A. L. Watson, "Sustainability Challenges and Opportunities in Oligonucleotide Manufacturing," J. Org. Chem, 2021, 86, 49-61.