An Efficient Synthesis of the Bicyclic Darunavir Side Chain Using Chemoenzymatic Catalysis

The Impact of Metagenomics on Biocatalysis

In the ever-growing demand for sustainable ways to produce high-value small molecules, biocatalysis has come to the forefront of greener routes to these chemicals. As such, the need to constantly find and optimise suitable biocatalysts for specific transformations has never been greater. Metagenome mining has been shown to rapidly expand the toolkit of promiscuous enzymes needed for new transformations, without requiring protein engineering steps. If protein engineering is needed, the metagenomic candidate can often provide a better starting point for engineering than a previously discovered enzyme on the open database or from literature, for instance. In this review, we highlight where metagenomics has made substantial impact on the area of biocatalysis in recent years. We review the discovery of enzymes in previously unexplored or 'hidden' sequence space, leading to the characterisation of enzymes with enhanced properties that originate from natural selection pressures in native environments.

Synthesis of Gamma-Butyrolactone Hormones Enables Understanding of Natural Product Induction

Bacteria produce natural products (NPs) via biosynthetic gene clusters. Unfortunately, many biosynthetic gene clusters are silent under traditional laboratory conditions. To access novel NPs, a better understanding of their regulation is needed. γ-Butyrolactones, including the A-factor and Streptomyces coelicolor butanolides, SCBs, are a major class of Streptomyces' hormones. Study of these hormones has been limited due to challenges in accessing them in stereochemically pure forms. Herein, we describe an efficient route to (R)-paraconyl alcohol, a key intermediate for these molecules, as well as a biocatalytic method to access the exocyclic hydroxyl group that differentiates A-factor-type from SCB-type hormones. Utilizing these methods, a library of hormones have been synthesized and tested in a green fluorescent protein reporter assay for their ability to relieve repression by the repressor ScbR. This allowed the most quantitative structure-activity relationship of γ-butyrolactones and a cognate repressor to date. Bioinformatics analysis strongly suggests that many other repressors of NP biosynthesis likely bind similar molecules. This efficient, diversifiable synthesis will enable further investigation of the regulation of NP biosynthesis.

Current Progress in the Chemoenzymatic Synthesis of Natural Products

Natural products, with their array of structural complexity, diversity, and biological activity, have inspired generations of chemists and driven the advancement of techniques in their total syntheses. The field of natural product synthesis continuously evolves through the development of methodologies to improve stereoselectivity, yield, scalability, substrate scope, late-stage functionalization, and/or enable novel reactions. One of the more interesting and unique techniques to emerge in the last thirty years is the use of chemoenzymatic reactions in the synthesis of natural products. This review highlights some of the recent examples and progress in the chemoenzymatic synthesis of natural products from 2019–2022.