TPDYs: strained macrocyclic diynes for bioconjugation processes

Area of Science:

• Organic Chemistry
• Chemical Biology
• Macromolecular Chemistry

Background:

• Strain-promoted azide-alkyne cycloaddition (SPAAC) is a key click chemistry reaction for bioconjugation.
• Development of novel cyclooctyne alternatives with unique reactivity and stability is ongoing.
• Macrocyclic scaffolds offer distinct structural and electronic properties compared to linear or small-ring systems.

Purpose of the Study:

• To synthesize and characterize a novel terphenyl diyne (TPDY) macrocycle.
• To evaluate the reactivity of the TPDY macrocycle in SPAAC and other cycloaddition reactions.
• To demonstrate the utility of TPDY for protein bioconjugation.

Main Methods:

• Synthesis of the 3,5-terphenyl diyne (TPDY) macrocycle.
• Investigation of SPAAC reactions with azides yielding atropisomeric triazoles.
• Exploration of cycloadditions with diazoacetates and tetrazines.
• Bioconjugation of TPDY to proteins using microbial transglutaminase.

Main Results:

• Successful synthesis of the bent 1,3-diyne containing TPDY macrocycle.
• TPDY demonstrated activity in SPAAC, forming atropisomeric triazole products.
• TPDY underwent cycloadditions with diazoacetates and tetrazines.
• Efficient bioconjugation of TPDY to two proteins was achieved via a microbial transglutaminase-catalyzed reaction.
• Stabilization of the TPDY diyne occurs through π and π* orbital interactions, unlike typical SPAAC reagents.

Conclusions:

• The developed TPDY macrocycle is a versatile building block for click chemistry.
• TPDY facilitates atropisomeric triazole formation and protein bioconjugation.
• The unique electronic stabilization of the diyne in TPDY expands the scope of SPAAC reagents.