Controllable Multihalogenation of a Non-native Substrate by the SyrB2 Iron Halogenase

Area of Science:

• Biocatalysis and Synthetic Chemistry
• Enzyme Engineering
• Organic Chemistry

Background:

• Multihalogenated functional groups are crucial in pharmaceuticals and natural products.
• Selective C-H bond functionalization remains a synthetic challenge.
• Biocatalysts offer precise control over chemical transformations.

Purpose of the Study:

• To explore the selective multihalogenation of unactivated C-H bonds using iron halogenases.
• To control the degree of halogenation (mono-, di-, tri-) on a non-native substrate.
• To enhance the yield of complex halogenated products and expand enzyme reactivity.

Main Methods:

• Utilized the nonheme iron halogenase SyrB2 for selective C-H halogenation.
• Controlled chemoselectivity by adjusting 2-oxoglutarate (2OG) cofactor and SyrB2 loading.
• Employed a ferredoxin-based reductant to enhance electron transfer and product yields.
• Investigated substrate steric hindrance effects on the degree of multihalogenation.

Main Results:

• Achieved controllable mono-, di-, and trichlorination of alpha-aminobutyric acid (Aba).
• Demonstrated order-of-magnitude yield enhancement for trichlorinated products using a biological reductant.
• Expanded SyrB2's scope to include multibromination and chemoenzymatic ethynyl group formation.
• Identified steric hindrance at the C4 carbon as a key factor controlling multihalogenation degree.

Conclusions:

• Iron halogenases, like SyrB2, can be engineered for selective multi-C-H functionalization.
• Biocatalytic strategies enable precise control over complex halogenation patterns.
• This work provides a platform for synthesizing valuable halogenated compounds for drug discovery and materials science.