A Solid-Phase Platform for Site-Specific Thiolation and Thioether Functionalization of DNA Oligonucleotides
- 1Department of Chemistry, University of Guelph, 50 Stone Rd E, Guelph, ON, N1G 2W1
Abstract
Thionucleobases provide distinctive hydrogen-bonding, electronic, and photochemical properties, but their site-specific incorporation into DNA often requires specialized sulfurcontaining phosphoramidites and multistep monomer synthesis. Here, we establish a unified protocol using sodium hydrosulfide (NaSH) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) for direct on-support conversion of 8-bromo-2′-deoxyadenosine (Br 8 dA) to 8-thio-2′deoxyadenosine (s 8 dA), late-stage C8 thioether diversification, and concurrent conversion of Br 8 dA and 4-triazolylthymidine within a single DNA strand. Electrophilic precursor nucleosides were incorporated by standard solid-phase synthesis and subsequently converted while the oligonucleotide remained support-bound. Conversion of Br 8 dA to s 8 dA was first demonstrated using 2-(trimethylsilyl)ethanethiol and subsequently achieved directly with NaSH·xH2O, eliminating the need for a separate fluoride-mediated deprotection step. Substitution at the C8 was compatible with mixed sequences, multiple modifications, and a range of aliphatic and aromatic thiols, enabling late-stage installation of diverse sulfurcontaining functionalities. Application of the same support-bound protocol to 4-triazolylthymidine afforded DNA containing one or more 4-thiothymidine (s 4 T) residues, and both thionucleobases could be generated within the same strand. Products were characterized by strong-anion-exchange high-performance liquid chromatography and electrospray ionization mass spectrometry. This workflow shifts sulfur installation from specialized monomer synthesis to a simple late-stage conversion and provides practical access to site-specifically thiolated and C8-thioether-functionalized DNA.
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BibTeX
@misc{saraya2026solidphase,
title = {{A Solid-Phase Platform for Site-Specific Thiolation and Thioether Functionalization of DNA Oligonucleotides}},
author = {Jagandeep S. Saraya and Nicholas G. Horton and Derek K. O'Flaherty},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008295/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008295/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - A Solid-Phase Platform for Site-Specific Thiolation and Thioether Functionalization of DNA Oligonucleotides
AU - Jagandeep S. Saraya
AU - Nicholas G. Horton
AU - Derek K. O'Flaherty
PY - 2026
DA - 2026/09/04
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008295/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008295/v1
AB - Thionucleobases provide distinctive hydrogen-bonding, electronic, and photochemical properties, but their site-specific incorporation into DNA often requires specialized sulfurcontaining phosphoramidites and multistep monomer synthesis. Here, we establish a unified protocol using sodium hydrosulfide (NaSH) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) for direct on-support conversion of 8-bromo-2′-deoxyadenosine (Br 8 dA) to 8-thio-2′deoxyadenosine (s 8 dA), late-stage C8 thioether diversification, and concurrent conversion of Br 8 dA and 4-triazolylthymidine within a single DNA strand. Electrophilic precursor nucleosides were incorporated by standard solid-phase synthesis and subsequently converted while the oligonucleotide remained support-bound. Conversion of Br 8 dA to s 8 dA was first demonstrated using 2-(trimethylsilyl)ethanethiol and subsequently achieved directly with NaSH·xH2O, eliminating the need for a separate fluoride-mediated deprotection step. Substitution at the C8 was compatible with mixed sequences, multiple modifications, and a range of aliphatic and aromatic thiols, enabling late-stage installation of diverse sulfurcontaining functionalities. Application of the same support-bound protocol to 4-triazolylthymidine afforded DNA containing one or more 4-thiothymidine (s 4 T) residues, and both thionucleobases could be generated within the same strand. Products were characterized by strong-anion-exchange high-performance liquid chromatography and electrospray ionization mass spectrometry. This workflow shifts sulfur installation from specialized monomer synthesis to a simple late-stage conversion and provides practical access to site-specifically thiolated and C8-thioether-functionalized DNA.
ER -