Acyl-peptide releasing enzyme from Sulfolobus tokodaii (ST0779) as a novel promiscuous biocatalyst for aldol addition

Hydrolase-Catalyzed Promiscuous Reactions and Applications in Organic Synthesis

The potential of biocatalysis becomes increasingly recognized as an efficient and green tool for modern organic synthesis. Biocatalytic promiscuity, a new frontier extended the use of enzymes in organic synthesis, has attracted much attention and expanded rapidly in the past decade. It focuses on the enzyme catalytic activities with unnatural substrates and alternative chemical transformations. Exploiting enzyme catalytic unconventional reactions might lead to improvements in existing catalysts and provide novel synthesis pathways that are currently not available. Among these enzymes, hydrolase (such as lipase, protease, acylase) undoubtedly has received special attention since they display remarkable activities for some unexpected reactions such as aldol reaction and other novel carbon-carbon and carbon-heteroatom bond-forming reactions. This chapter introduces the recent progress in hydrolase catalytic unconventional reactions and application in organic synthesis. Some important examples of hydrolase catalytic unconventional reactions in addition reactions are reviewed, highlighting the catalytic promiscuity of hydrolases focuses on aldol reaction, Michael addition, and multicomponent reactions.

Miniemulsion in biocatalysis, a new approach employing a solid reagent and an easy protocol for product isolation applied to the aldol reaction by Rhizopus niveus lipase

Miniemulsion systems presented a great potential for biocatalytic reactions. However, different limitations jeopardized the applications of this non-conventional medium. In this work, miniemulsion systems (emulsion reactors) were applied for the first time to the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde by Rhizopus niveus lipase allowing a decrease in the catalyst concentration from 20 mg mL^-1 to 6 mg mL^-1 in comparison with organic solvents. Moreover, the yield increased from ~25% to ~65% for 48 h reactions and the enantiomeric excess increased from ~10% to ~30% for (R,S)-anti-aldol product, showing the potentiality of this non-conventional reaction medium. The advances reported in this work expands the possibilities of the miniemulsion reaction medium to a whole new level, increasing the scope to solid reagents and products, and also different reactions (biocatalytic or not) that requires pH control by buffers with a simple product isolation procedure, enabling future applications of this poorly studied reaction medium.