Enzyme-Promoted Direct Asymmetric Michael Reaction by Using Protease from Streptomyces griseus

Lipase-Catalyzed Michael Addition in 'Water-like' Ionic Liquids and Tertiary Amides: What Is the Role of the Enzymes?

Michael addition is an important reaction to form C-C bonds. Different hydrolases (e.g., lipases, proteases, and d-aminoacylase) have been reported to catalyze C-C-forming reactions, but the reaction mechanism is not entirely clear. This study examined several model Michael reactions catalyzed by lipases and amino acids in various solvents and found that "water-like" functionalized ionic liquids (ILs) increased the reaction yield to 35-55% from 30% in triglyme and 17% in [BMIM][Tf2N]. Interestingly, tertiary amides as solvents remarkably increased the reaction yield (to up to 65-85%) and enantioselectivity (up to 71-84% ee) when catalyzed by porcine pancreatic lipase (PPL). Our experimental, spectroscopic, and computational studies discovered that the lipase catalysis can be attributed to basic amino acid residues as the catalysts to promote Michael addition, especially when tertiary amide solvents partially unfold the protein and expose its (basic) amino acid residues.

Recent advances in enzymatic carbon-carbon bond formation

Enzymatic carbon-carbon (C-C) bond formation reactions have become an effective and invaluable tool for designing new biological and medicinal molecules, often with asymmetric features. This review provides a systematic overview of key C-C bond formation reactions and enzymes, with the focus of reaction mechanisms and recent advances. These reactions include the aldol reaction, Henry reaction, Knoevenagel condensation, Michael addition, Friedel-Crafts alkylation and acylation, Mannich reaction, Morita-Baylis-Hillman (MBH) reaction, Diels-Alder reaction, acyloin condensations via Thiamine Diphosphate (ThDP)-dependent enzymes, oxidative and reductive C-C bond formation, C-C bond formation through C1 resource utilization, radical enzymes for C-C bond formation, and other C-C bond formation reactions.

Novel aminoacylases from Streptomyces griseus DSM 40236 and their recombinant production in Streptomyces lividans

Amino acid-based surfactants are valuable compounds for cosmetic formulations. The chemical synthesis of acyl amino acids is conventionally performed by the Schotten-Baumann reaction using fatty acyl chlorides, but aminoacylases have also been investigated for use in biocatalytic synthesis with free fatty acids. Aminoacylases and their properties are diverse; they belong to different peptidase families and show differences in substrate specificity and biocatalytic potential. Bacterial aminoacylases capable of synthesis have been isolated from Burkholderia, Mycolicibacterium, and Streptomyces. Although several proteases and peptidases from S. griseus have been described, no aminoacylases from this species have been identified yet. In this study, we investigated two novel enzymes produced by S. griseus DSM 40236T . We identified and cloned the respective genes and recombinantly expressed an α-aminoacylase (EC3.5.1.14), designated SgAA, and an ε-lysine acylase (EC3.5.1.17), designated SgELA, in S. lividans TK23. The purified aminoacylase SgAA was biochemically characterized, focusing on its hydrolytic activity to determine temperature- and pH optima and stabilities. The aminoacylase could hydrolyze various acetyl amino acids at the Nα -position with a broad specificity regarding the sidechain. Substrates with longer acyl chains, like lauroyl amino acids, were hydrolyzed to a lesser extent. Purified aminoacylase SgELA specific for the hydrolysis of Nε -acetyl-l-lysine was unstable and lost its enzymatic activity upon storage for a longer period but could initially be characterized. The pH optimum of SgELA was pH 8.0. While synthesis of acyl amino acids was not observed with SgELA, SgAA catalyzed the synthesis of lauroyl-methionine.

Total Synthesis of Acaulide and Acaulone A

Acaulide and acaulone A, which contain 14-membered macrodiolides, were isolated from a culture of Acaulium sp. H-JQSF. The antiosteoporosis activity of acaulide is expected to contribute to drug discovery research for an aging society. We herein report the first total synthesis of acaulide, acaulone A, and 10-keto-acaudiol A. Acaulide and acaulone A were synthesized via the late stage Michael addition to the 14-membered macrodiolide, which was inspired by plausible biosynthetic pathways. This approach succeeded in the construction of the acaulide skeleton, which revealed the specific conformation of the 14-membered macrodiolide for late stage functionalization.

Rendering classical hydrophilic enantiopure Werner salts [M(en)3]n+nX- lipophilic (M/n = Cr/3, Co/3, Rh/3, Ir/3, Pt/4); new chiral hydrogen bond donor catalysts and enantioselectivities as a function of metal and charge

Known hydrophilic halide salts of the title compounds are converted to new lipophilic BArf- (B(3,5-C6H3(CF3)2)4-) salts. These are isolated as hydrates (Λ- or Δ-[M(en)3]n+nBArf-·zH2O; z = 17-9) and characterized by NMR (acetone-d6) and microanalyses. Thermal stabilities are probed by capillary thermolyses and TGA and DSC measurements (onset of dehydration 71-151 °C). In the presence of tertiary amines, they are effective catalysts for enantioselective Michael type carbon-carbon or carbon-nitrogen bond forming additions of 1,3-dicarbonyl compounds (acceptors: trans-β-nitrostyrene, di-tert-butylazodicarboxylate, 2-cyclopenten-1-one; average ee = 33%, 52%, 17%). Effects of the metal and charge upon enantioselectivities are analyzed. A number of properties appear to correlate to the NH Brønsted acidity order ([Pt(en)3]4+ > [Cr(en)3]3+ > [Co(en)3]3+ > [Rh(en)3]3+ > [Ir(en)3]3+).