Lactones. 6. Microbial lactonization of gamma,delta-epoxy esters

Area of Science:

• Biocatalysis and Enzyme Technology
• Organic Chemistry
• Microbial Transformation

Background:

• Chiral hydroxy lactones are valuable building blocks in organic synthesis.
• Enantioselective synthesis of these compounds remains a challenge.
• Microbial transformations offer a sustainable approach to chiral synthesis.

Purpose of the Study:

• To evaluate the potential of 19 microorganisms for the enantioselective lactonization of racemic gamma,delta-epoxy esters.
• To identify microbial strains capable of producing specific enantiomers of hydroxy lactones with high enantiomeric excess (ee).

Main Methods:

• Screening of 19 microbial strains for their ability to catalyze lactonization of epoxy esters 3a and 3b.
• Analysis of product enantiomeric excess (ee) using chiral chromatography.
• Identification of the most effective microorganisms for enantioselective lactone formation.

Main Results:

• Rhodotorula rubra preferentially transformed epoxy esters 3a and 3b into (-)-trans delta-hydroxy-gamma-lactones with ee of 76% and 24%, respectively.
• Botrytis cinerea and Fusarium semitectum demonstrated high efficiency (20-30%) and enantioselectivity (ee 60-100%) in forming (-)-gamma-hydroxy-delta-lactones 6a and 6b.
• Significant variations in enantioselectivity were observed among the tested microorganisms.

Conclusions:

• Microbial enantioselective lactonization is a viable strategy for synthesizing chiral hydroxy lactones.
• Specific microorganisms like Rhodotorula rubra, Botrytis cinerea, and Fusarium semitectum show promise for industrial applications in chiral synthesis.
• Further optimization of reaction conditions could enhance the efficiency and enantioselectivity of these biotransformations.