Sydnone-based prosthetic groups for radioiodination.

Area of Science:

• Chemical Biology
• Radiochemistry
• Organic Synthesis

Background:

• Bioorthogonal reactions are crucial for labeling biomolecules in vivo.
• Radioiodination is vital for developing diagnostic and therapeutic radiopharmaceuticals.
• Strained-Promoted Sydnone-Alkyne Cycloaddition (SPSAC) presents a novel bioorthogonal strategy.

Purpose of the Study:

• To evaluate the potential of SPSAC for efficient radioiodination.
• To optimize sydnone structures for enhanced reaction kinetics.
• To demonstrate the application of SPSAC in radiolabeling peptides.

Main Methods:

• Synthesis of various sydnone derivatives with different substitutions.
• Kinetic studies using non-radioactive iodinated compounds.
• Copper-catalyzed nucleophilic substitution for 125I-labeled sydnone synthesis.
• Application of SPSAC under radiotracer conditions on cyclooctyne-conjugated peptides.

Main Results:

• An arylsydnone with a C4-chlorine substitution showed superior reaction kinetics.
• Reaction rates up to 11 times higher than azide-based methods were achieved.
• High-efficiency synthesis of 125I-labeled sydnones from arylboronic acid precursors.
• Rapid (<1 hour) and efficient peptide labeling using SPSAC under radiotracer conditions.

Conclusions:

• SPSAC is a promising bioorthogonal reaction for heavy halogen radiolabeling.
• Optimized SPSAC systems facilitate rapid and efficient radiopharmaceutical production.
• This method expands the toolkit for developing novel radiotracers for imaging and therapy.