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Bioorganic Chemistry(Chemistry)

Osawa TakashiAssistant professor

Since starting the synthetic research on 2',4'-bridged nucleic acids in the department of bioorganic chemistry (Professor Obika) in 2009, I have been consistently advancing research related to nucleic acid chemistry. With the vigorous progress of research on the development of nucleic acid drugs targeting RNA as a therapeutic target and the increasing importance of nucleic acid chemical modification technology in recent years, I’m studying with the students belonging to Professor Obika’s laboratory. I would like to contribute to the development of nucleic acid medicine.

Research theme

Research on the synthesis of nucleic acids with fixed conformations of the sugar and phosphate moieties of oligonucleotides

Artificial nucleic acids with constrained sugar and phosphate moieties of oligonucleotides has excellent target RNA binding ability. On the other hand, artificial nucleic acids having an appropriately fixed conformation generally have a complicated structure and therefore have difficulty in synthesizing. In this study, we are designing several types of artificial nucleic acids in which the conformation of the sugar and phosphate parts is fixed by a simple bicyclic sugar part skeleton, and we are proceeding with their synthesis and evaluation of their physical properties.

Development of the reactions that enable efficient supply of various chemically modified oligonucleotides

If the structure-activity relationship of oligonucleotide medicines can be clarified, it will be possible to logically design oligonucleotide medicines. However, since the derivatization of oligonucleotides is difficult, it is necessary to develop a method that can easily and efficiently supply a wide variety of modified oligonucleotides. Therefore, we are developing chemical reactions that selectively transforms the structure of the part to be chemically modified.

Representative achievements

Osawa, T.; Kawaguchi, M.; Jang, Y.-J.; Ito, Y.; Hari, Y. “Synthesis and properties of oligonucleotides bearing thymidine derivatives with 1,6-dioxaspiro[4.5]decane skeleton” Bioorg. Med. Chem. 2021, 31, 115966.

Osawa, T.; Onishi, Y.; Wakita, S.; Ito, Y.; Hari, Y. “Synthesis and hybridization properties of oligonucleotides including 2′-C,4′-C-ethyleneoxy-bridged 2′-deoxyadenosine with an exocyclic methylene unit” Heterocycles 2020, 101, 284–297.

Osawa, T.; Kim, H.; Shoji, M.; Saijo, M.; Dohi, M.; Ito, Y.; Obika, S.; Hari, Y. “Synthesis of 2'-C,4'-C-methyleneoxy-bridged thymidine derivative and properties of modified oligonucleotides” J. Org. Chem. 2019, 84, 13336–13342.

Osawa, T.; Hitomi, Y.; Wakita, S.; Kim, H.; Ito, Y.; Hari, Y. “Synthesis and hybridizing properties of isoDNAs including 3'-O,4'-C-ethyleneoxy-bridged 5-methyluridine derivatives” Bioorg. Med. Chem. 2018, 26, 3875–3881.

Osawa, T.; Sawamura, M.; Wada, F.; Yamamoto, T.; Obika, S.; Hari, Y. “Synthesis, duplex-forming ability, enzymatic stability and in vitro antisense potency of oligonucleotides including 2'-C,4'-C-ethyleneoxy-bidged thymidine derivatives” Org. Biomol. Chem. 2017, 15, 3955–3963.

Osawa, T.; Obika, S.; Hari, Y. “Synthesis and properties of novel 2ʹ-C,4ʹ-C-ethyleneoxy-bridged 2ʹ-deoxyribonucleic acids with exocyclic methylene groups (methylene-EoDNAs)” Org. Biomol. Chem. 2016, 14, 9481–9484.

Osawa, T.; Hari, Y.; Dohi, M.; Matsuda, Y.; Obika, S. “Synthesis and properties of 5-methyluridine derivatives with 3,4-dihydro-2H-pyran-bridge” J. Org. Chem. 2015, 80, 10474–10481.