Bioorthogonal prodrug activation driven by a strain-promoted 1,3-dipolar cycloaddition

Area of Science:

• Bioorthogonal Chemistry
• Organic Synthesis
• Chemical Biology

Background:

• The 1,3-dipolar cycloaddition between azides and trans-cyclooctene (TCO) was previously disregarded due to hydrolysis-susceptible adducts.
• This instability hindered its application in bioorthogonal chemistry.

Purpose of the Study:

• To utilize the adduct instability for a novel prodrug activation strategy.
• To explore the application of this reaction in organic synthesis as a protecting group strategy.

Main Methods:

• Investigated the 1,3-dipolar cycloaddition reaction between trans-cyclooctenol (TCO-OH) and a model prodrug.
• Utilized 1H NMR spectroscopy to study the reaction mechanism and intermediate hydrolysis.
• Assessed the in vitro cytotoxicity of an activated doxorubicin prodrug.

Main Results:

• The reaction proceeded rapidly with second-order rates for TCO-OH isomers, releasing the active compound.
• Hydrolysis of triazoline and imine intermediates was confirmed as the drug release mechanism.
• Restored cytotoxicity of a doxorubicin prodrug in vitro upon activation with TCO-OH.
• No activation was observed with cis-cyclooctenol (CCO-OH).

Conclusions:

• The instability of TCO-adducts can be advantageously employed for prodrug activation.
• This method offers a mild and orthogonal protecting group strategy for amino and hydroxyl groups in organic synthesis.
• The reaction shows promise for targeted drug delivery and bioconjugation applications.