Unusual propargylic oxidations catalyzed by chloroperoxidase

Area of Science:

• Biochemistry
• Organic Chemistry

Background:

• Chloroperoxidase (CPO) is a versatile heme enzyme known for its oxidative capabilities.
• Previous studies have focused on CPO's halogenation and epoxidation activities.

Purpose of the Study:

• To investigate and characterize a novel oxidative transformation catalyzed by chloroperoxidase.
• To explore the potential of CPO in propargylic oxidation reactions.

Main Methods:

• Enzymatic oxidation of various 2-alkynes using chloroperoxidase.
• Utilized hydrogen peroxide and t-butyl hydroperoxide as terminal oxidants.
• Characterization of reaction products, including alcohol intermediates and aldehydes.

Main Results:

• Chloroperoxidase effectively catalyzes the oxidation of 2-alkynes to aldehydes.
• The reaction proceeds via alcohol intermediates, with the alkyne triple bond remaining intact.
• A free radical mechanism is proposed for the initial hydroxylation step.

Conclusions:

• Propargylic oxidation represents a new enzymatic activity for chloroperoxidase.
• This finding expands the known catalytic repertoire of chloroperoxidase.
• The proposed mechanism provides insight into the enzyme's reactivity with alkynes.