Inverse Electron-Demand Diels-Alder Bioconjugation Reactions Using 7-Oxanorbornenes as Dienophiles

Area of Science:

• Bioorthogonal chemistry
• Organic synthesis
• Click chemistry

Background:

• Inverse electron-demand Diels-Alder (IEDDA) reactions are crucial for bioorthogonal conjugation.
• Developing efficient and stereoselective dienophiles is essential for expanding IEDDA applications.
• 7-Oxanorbornene offers unique reactivity as a dienophile in IEDDA cycloadditions.

Purpose of the Study:

• To synthesize novel conjugates using 7-oxanorbornene as a dienophile in IEDDA reactions.
• To evaluate the efficiency and stereoselectivity of IEDDA reactions involving 7-oxanorbornene.
• To demonstrate the utility of this method for conjugating biomolecules and probes.

Main Methods:

• Incorporation of 7-oxanorbornene into oligonucleotides, peptides, and peptide nucleic acids.
• Reaction of 7-oxanorbornene-containing molecules with tetrazines linked to peptides, d-biotin, BODIPY, or N-acetyl-d-galactosamine.
• Performing inverse electron-demand Diels-Alder (IEDDA) cycloaddition reactions overnight at 37 °C.

Main Results:

• Target conjugates were successfully synthesized in good yields via IEDDA cycloaddition.
• IEDDA reactions utilizing 7-oxanorbornenes produced a reduced number of stereoisomers compared to other dienophiles.
• The method proved effective for conjugating diverse molecules, including biomolecules and imaging agents.

Conclusions:

• 7-Oxanorbornene is an effective dienophile for IEDDA cycloadditions, enabling efficient conjugate synthesis.
• This approach offers improved stereochemical control in IEDDA reactions.
• The developed methodology expands the toolkit for bioorthogonal chemistry and bioconjugation.