Mechanistic differences between linear vs. spirocyclic dialkyldiazirine probes for photoaffinity labeling

Area of Science:

• Photochemistry
• Chemical Biology
• Organic Chemistry

Background:

• Dialkyldiazirines are photo-reactive probes for interactome mapping.
• Linear dialkyldiazirines yield carbenes and diazoalkanes upon photolysis.
• The mechanism of cyclobutanediazirine photolysis, particularly the role of diazo intermediates, was unclear.

Purpose of the Study:

• To elucidate the photochemical mechanism of cyclobutanediazirines.
• To compare the reactivity of cyclobutanediazirines with linear diazirines.
• To assess the impact of cyclobutanediazirine photochemistry on protein labeling.

Main Methods:

• Photolysis of cyclobutanediazirines and linear diazirines at 365 nm.
• Detection of reaction products (e.g., cyclobutylidene adducts, methylenecyclopropane derivatives).
• Chemical proteomic studies to evaluate protein labeling efficiency.

Main Results:

• Cyclobutanediazirine photolysis generates cyclobutylidene intermediates, evidenced by specific reaction products.
• Unlike linear diazirines, cyclobutanediazirines did not produce detectable diazo compounds.
• Cyclobutanediazirine probes showed reduced protein labeling compared to linear diazirine probes.

Conclusions:

• Cyclobutanediazirine photolysis proceeds mainly via carbene intermediates with minimal diazo formation.
• This contrasts with linear diazirines, where diazoalkane alkylation is significant.
• The carbene-dominant pathway influences the utility of cyclobutanediazirines in chemical biology applications.