Hen egg white lysozyme encapsulated in ZIF-8 for performing promiscuous enzymatic Mannich reaction

Hen egg white lysozyme (HEWL) was exploited for the synthesis of β-amino carbonyl compounds through a direct and three-component Mannich reaction in aqueous, confirming high chemoselectivity toward imine. In order to further extend the applications of the enzyme, HEWL was encapsulated using a metal-organic framework (MOF). The reactivity, stereoselectivity, and reusability of the encapsulated enzyme were investigated. The reaction was significantly enhanced as compared to the non-encapsulated enzyme. A mutated version of the enzyme, containing Asp52Ala (D52A), lacking important catalytical residue, has lost the bacterial site activity against Micrococcus luteus (M. luteus) while the D52A variant displayed an increased rate of the Mannich reaction, indicating a different catalytical residue involved in the promiscuous reaction. Based on site-directed mutagenesis, molecular docking, and molecular dynamic studies, it was proposed that π-stacking, H-bond interactions, and the presence of water in the active site may play crucial roles in the mechanism of the reaction.

Stereoselective Domino Reactions in the Synthesis of Spiro Compounds

This review summarizes the latest developments in asymmetric domino reactions, with the emphasis on the preparation of spiro compounds. Discussions on the stereoselectivity of the transformations, the reaction mechanisms, the rationalization of the stereochemical outcome, and the applications of domino reactions to the synthesis of biologically active molecules and natural products are included when appropriate.

1 Introduction

2 Asymmetric Domino Reactions

2.1 Domino Reactions Initiated by Michael Reactions

2.2 Domino Reactions Initiated by Mannich Reactions

2.3 Domino Reactions Initiated by Knoevenagel Reactions

2.4 Domino Reactions Initiated by Cycloaddition Reactions

2.5 Domino Reactions Initiated by Metal Insertion

2.6 Other Mechanisms

3 Conclusion

Crystal structure of 2-(2,5-di-meth-oxy-phen-yl)benzo[d]thia-zole

The title compound, C15H13NO2S, was synthesized efficiently in the solid state by exploiting pepsin catalysis. The ring systems are nearly coplanar [inter-planar angle of 5.38 (2)°] with an associated intra-molecular S⋯O=C short contact of 2.7082 (4) Å. The packing involves C-H⋯O, C-H⋯π and π-π contacts.

Asymmetric oxidative Mannich reactions promoted by photocatalysis and electrochemistry

The asymmetric Mannich reaction is an essential method in contemporary organic chemistry. As a representative of clean and green synthesis methods, photochemical and electrochemical oxidation strategies have re-emerged in recent years, providing new ideas for asymmetric Mannich reactions. Numerous chiral β-amino carbonyl compounds have been accessed in satisfactory yields with excellent enantioselectivity via such novel asymmetric oxidative Mannich reactions. This minireview highlights plentiful advances in asymmetric oxidative Mannich reactions that rely on photoredox or anodic-oxidation and covers the literature from 2014 to date. Furthermore, the future development of this field is envisaged.

2-Aryl-6-Polyfluoroalkyl-4-Pyrones as Promising RF-Building-Blocks: Synthesis and Application for Construction of Fluorinated Azaheterocycles

A convenient and general method for the direct synthesis of 2-aryl-6-(trifluoromethyl)-4-pyrones and 2-aryl-5-bromo-6-(trifluoromethyl)-4-pyrones has been developed on the basis of one-pot oxidative cyclization of (E)-6-aryl-1,1,1-trifluorohex-5-ene-2,4-diones via a bromination/dehydrobromination approach. This strategy was also applied for the preparation of 2-phenyl-6-polyfluoroalkyl-4-pyrones and their 5-bromo derivatives. Conditions of chemoselective enediones bromination were found and the key intermediates of the cyclization of bromo-derivatives to 4-pyrones were characterized. Synthetic application of the prepared 4-pyrones has been demonstrated for the construction of biologically important CF3-bearing azaheterocycles, such as pyrazoles, pyridones, and triazoles.

Enzyme and photoredox sequential catalysis for the synthesis of 1,3-oxazine derivatives in one pot

A novel strategy combining visible-light and enzyme catalysis for the synthesis of 1,3-oxazine derivatives is described for the first time.