Total synthesis of (±)-fumimycin and analogues for biological evaluation as peptide deformylase inhibitors

Design, synthesis, and evaluation of 1,4-benzothiazine-3-one containing bisamide derivatives as dual inhibitors of Staphylococcus aureus with plausible application in a urinary catheter

In this study, 1,4-benzothiazine-based bisamide derivatives, a new class of antibacterial agents targeting bacterial peptide deformylase (PDF), were designed and synthesized to combat Staphylococcus aureus infection. Molecular modeling of the designed molecules showed better docking scores compared to the natural product actinonin. Bioactivity assessment identified two derivatives with promising antibacterial activity in vitro. The stability of the most active molecule, 8bE, was assessed using molecular dynamics (MD) simulation. Significantly, compound 8bE could also inhibit the S. aureus biofilm at low concentrations. Furthermore, the capability of the synthesized molecule to inhibit S. aureus biofilm formation on medical devices like urinary catheters is also demonstrated.

One-pot domino syntheses of 3-alkyl-3-N-substituted aminobenzofuran-2(3H)-ones based on alkali-promoted Michael addition and lactonization

In this paper, a novel cascade reaction of caesium carbonate-promoted Michael addition and lactonization for the one-pot synthesis of 3-alkyl-3-N-substituted aminobenzofuran-2(3H)-one derivatives has been established based on the screening of the alkaline reagents and optimization of reaction conditions, in which the N-substituted (ortho-hydroxy)aryl glycine esters were used as the Michael donors to react with different α, β-unsaturated carbonyl compounds. In the case of using the asymmetric starting material, the epimers could be successfully separated by conventional chromatography. In addition, plausible mechanisms were suggested and the absolute configuration of the epimer was analysed. All the chemical structures of unreported benzofuran-2(3H)-one derivatives were characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, IR and high-resolution mass spectrometry (HRMS).

Steglich esterification: A versatile synthetic approach toward the synthesis of natural products, their analogues/derivatives

The exploitation of natural products and their analogues in the field of pharmacology has been regarded as of great importance. It can be attributed to the fact that these scaffolds exhibit diverse chemical properties, distinct biological activities and zenith specificity in their biochemical processes, enabling them to act as favorable structures for lead compounds. The synthesis of natural products has been a crafty and hard-to-achieve task. Steglich esterification reaction has played a significant role in that area. It is a mild and efficient technique for constructing ester linkages. This technique involves the establishment of ester moiety via a carbodiimide-based condensation of a carboxylic acid with an alcohol, thiol or an amine catalyzed by dimethyl aminopyridine (DMAP). Specifically, labile reagents with multiple reactive sites are esterified efficiently with the classical and modified Steglich esterification conditions, which accounts for their synthetic utility. This review encloses the performance of the Steglich esterification reaction in forging the ester linkage for executing the total synthesis of natural products and their derivatives since 2018.

Cu-catalyzed asymmetric regiodivergent electrosynthesis and its application in the enantioselective total synthesis of (-)-fumimycin

Quaternary amino acids are one of the essential building blocks and precursors of medicinally important compounds. Various synthetic strategies towards their synthesis have been reported. On the other hand, developing core-structure-oriented cross-dehydrogenative coupling (CDC) reactions, is a largely unsolved problem. Herein, we describe a copper-catalyzed regiodivergent electrochemical CDC reaction of Schiff bases and commercially available hydroquinones to obtain three classes of chiral quaternary amino acid derivatives for the efficient assembly of complex scaffolds with excellent stereocontrol. The electrochemical anodic oxidation process with slow releasing of quinones serves as an internal syringe pump and provides high levels of reaction efficiency and enantiomeric control. The utility of this strategy is highlighted through the synthetic utility in the asymmetric total synthesis of (-)-fumimycin.

In the Pursuit of (Ald)Imine Surrogates for the Direct Asymmetric Synthesis of Non-Proteinogenic α-Amino Acids

Nature remarkably employs posttranslational modifications of the 20 canonical α-amino acids to devise a far larger structural, conformational, and functional diversity found in non-proteinogenic amino acids (NPAAs), which ultimately translates into a plethora of complex biological functions. Synthetic chemists are continuously trying to reproduce and even extrapolate the repertoire of NPAA building blocks to build structural diversity into bioactive molecules and materials. The direct asymmetric functionalization of α-imino esters represents one of the most robust and attractive routes to NPAAs. This review summarizes the most prominent examples of bench-stable (ald)imine surrogates exploited for the synthesis of NPAAs, including our most recent results in the nucleophilic substitution of α-haloglycines and other α-halo­aminals. A synopsis of kinetic studies, reaction optimizations, and enantio­selective catalytic methods is also presented.

1 Introduction

2 Asymmetric Synthesis of Tertiary α-Substituted NPAAs

2.1 From N,O-Acetals (α-Hydroxy/Alkyloxy/Acetoxyglycines)

2.2 From α-Amido Sulfones

2.3 From α-Haloglycine Esters

2.4 From N,O-Bis(Boc) Hydroxyglycine

3 Asymmetric Synthesis of Acyclic Quaternary α,α-Disubstituted NPAAs

4 Concluding Remarks

Cross-coupling reactions towards the synthesis of natural products

Cross-coupling reactions are powerful synthetic tools for the formation of remarkable building blocks of many naturally occurring molecules, polymers and biologically active compounds. These reactions have brought potent transformations in chemical and pharmaceutical disciplines. In this review, we have focused on the use of cross-coupling reactions such as Suzuki, Negishi, Heck, Sonogashira and Stille in the total synthesis of some natural products of recent years (2016-2020). A short introduction of mentioned cross-coupling reactions along with highlighted aspects of natural products has been stated in separate sections. Additionally, few examples of natural products via incorporation of more than one type of cross-coupling reaction have also been added to demonstrate the importance of these reactions in organic synthesis.

Concise and Convergent Enantioselective Total Syntheses of (+)- and (-)-Fumimycin

The concise and convergent total syntheses of (+)- and (-)-Fumimycin have been achieved by taking advantage of strategies for the asymmetric aza-Friedel-Crafts reaction of a highly substituted hydroquinone and N-fumaryl ketimine generated from the corresponding dehydroalanine. The enantiomerically pure natural product and its enantiomer were prepared in seven steps and 22% overall yield by employing both enantiomers of a BINOL-derived chiral phosphoric acid (CPA) catalyst.