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Biocatalysis is a branch of catalysis that exploits enzymes to perform highly stereoselective chemical transformations under mild and sustainable conditions. This Synpact highlights how biocatalysis can be used in the synthesis of chiral 1,3-mercaptoalkanols, an important class of compounds responsible for the flavours and aromas of many foods and beverages. The identification of two ketoreductase (KRED) enzymes able to reduce prochiral ketone precursors enantioselectively to 1,3-mercaptoalkanols bearing a C–O stereocentre is presented. In addition, the combination of a photocatalytic thia-Michael reaction to access prochiral ketones with subsequent KRED-biocatalysed reduction in a one-pot cascade is presented. Photo-biocatalysed cascades represent one of the new and most intriguing challenges in synthetic chemistry, because the combination of different catalytic methodologies in domino processes offers unique opportunities to outperform sequential reactions with a high degree of selectivity and the avoidance of the need to isolate reaction intermediates. 1 Introduction 2 Biocatalytic Synthesis of 1,3-Mercaptoalkanols 3 Photo-Biocatalytic Synthesis of 1,3-Mercaptoalkanols 4 Photo-Biocatalysed Cascade Reactions 5 Conclusions [ABSTRACT FROM AUTHOR]

Chiral β-hydroxysulfides are an important class of organic compounds which find broad application in organic and pharmaceutical chemistry. Herein we describe the development of novel biocatalytic and chemoenzymatic methods for the enantioselective synthesis of β-hydroxysulfides by exploiting ketoreductase (KRED) enzymes. Four KREDs were discovered from a pool of 384 enzymes identified and isolated through a metagenomic approach. KRED311 and KRED349 catalysed the synthesis of β-hydroxysulfides bearing a stereocentre at the C-O bond with opposite absolute configurations and excellent ee values by novel chemoenzymatic and biocatalytic-chemical-biocatalytic (bio-chem-bio) cascades starting from commercially available thiophenols/thiols and α-haloketones/alcohols. KRED253 and KRED384 catalysed the enantioselective synthesis of β-hydroxysulfides bearing a stereocentre at the C-S bond with opposite enantioselectivities by dynamic kinetic resolution (DKR) of racemic α-thioaldehydes., (© 2022 Wiley-VCH GmbH.)

The enantioselective synthesis of α-thiocarboxylic acids by biocatalytic dynamic kinetic resolution (DKR) of nitrile precursors exploiting nitrilase enzymes is described. A panel of 35 nitrilase biocatalysts were screened and enzymes Nit27 and Nit34 were found to catalyse the DKR of racemic α-thionitriles under mild conditions, affording the corresponding carboxylic acids with high conversions and good-to-excellent ee. The ammonia produced in situ during the biocatalytic transformation favours the racemization of the nitrile enantiomers and, in turn, the DKR without the need of any external additive base., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Novel amidinourea derivatives have been synthesised and evaluated for their antiviral activity against Hepatitis C Virus (HCV). A compound with an amidinourea-spermine chemical structure, different from that of standard anti-HCV drugs, showed micromolar activity against HCV and excellent viability. Studies on the mode of action revealed that the new compound may act against HCV through the inhibition of IRES-mediated translation., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)