Copper Complexes with Protein-Based N-Donor Ligands as cis-Selective Nascent Cyclopropanases.

Area of Science:

• Biocatalysis
• Protein Engineering
• Organometallic Chemistry

Background:

• Protein engineering offers a powerful approach to designing novel catalysts.
• Cupin proteins provide a versatile scaffold for developing metalloenzymes.
• Cyclopropanation reactions are crucial in organic synthesis.

Purpose of the Study:

• To engineer protein-based metal ligands for cis-selective cyclopropanation.
• To utilize the TM1459 cupin protein superfamily as a scaffold for catalyst development.
• To enhance catalytic activity and selectivity through protein modification.

Main Methods:

• Site-directed mutagenesis of TM1459 cupin proteins to introduce metal-binding sites.
• Complexation of copper ions to engineered protein mutants.
• Catalytic evaluation of copper-protein complexes in cyclopropanation reactions.
• Optimization of secondary coordination sphere residues to improve selectivity.

Main Results:

• TM1459 mutants with a 3-His metal-binding site effectively catalyzed cyclopropanation with high diastereoselectivity.
• Copper complexes exhibited excellent catalytic performance with styrene and ethyl diazoacetate.
• Further mutations enhanced cis-selectivity up to an 80:20 cis:trans ratio using t-butyl diazoacetate.
• High enantioselectivity (90% ee) was achieved with optimized protein ligands.

Conclusions:

• Protein-based metal ligands can be successfully engineered for selective catalytic transformations.
• The TM1459 cupin scaffold is suitable for developing novel metalloenzymes.
• This work provides a foundation for designing highly selective biocatalysts for cyclopropanation and other organic reactions.