Resonance-assisted hydrogen bonding (RAHB), a concept introduced by Gilli and co-workers in 1989, concerns a kind of intramolecular H-bonding strengthened by a conjugated π-system, usually in 6-, 8-, or 10-membered rings. This Review highlights the involvement of RAHB as a driving force in the synthesis of organic, coordination, and organometallic compounds, as a handy tool in the activation of covalent bonds, and in starting moieties for synthetic transformations. The unique roles of RAHB in molecular recognition and switches, E/Z isomeric resolution, racemization and epimerization of amino acids and chiral amino alcohols, solvatochromism, liquid-crystalline compounds, and in synthons for crystal engineering and polymer materials are also discussed. The Review can provide practical guidance for synthetic chemists that are interested in exploring and further developing RAHB-assisted synthesis and design of materials.

Resonance‐Assisted Hydrogen Bonding as a Driving Force in Synthesis and a Synthon in the Design of Materials

Esterases form a diverse class of enzymes of largely unknown physiological role. Because many drugs and pesticides carry ester functions, the hydrolysis of such compounds forms at least one potential biological function. Carboxylesterases catalyze the hydrolysis of short chain aliphatic and aromatic carboxylic ester compounds. Esterases, D-alanyl-D-alanine-peptidases (DD-peptidases) and beta-lactamases can be grouped into two distinct classes of hydrolases with different folds and topologically unrelated catalytic residues, the one class comprising of esterases, the other one of beta-lactamases and DD-peptidases. The chemical reactivities of esters and beta-lactams towards hydrolysis are quite similar, which raises the question of which factors prevent esterases from displaying beta-lactamase activity and vice versa. Here we describe the crystal structure of EstB, an esterase isolated from Burkholderia gladioli. It shows the protein to belong to a novel class of esterases with homology to Penicillin binding proteins, notably DD-peptidase and class C beta-lactamases. Site-directed mutagenesis and the crystal structure of the complex with diisopropyl-fluorophosphate suggest Ser75 within the "beta-lactamase" Ser-x-x-Lys motif to act as catalytic nucleophile. Despite its structural homology to beta-lactamases, EstB shows no beta-lactamase activity. Although the nature and arrangement of active-site residues is very similar between EstB and homologous beta-lactamases, there are considerable differences in the shape of the active site tunnel. Modeling studies suggest steric factors to account for the enzyme's selectivity for ester hydrolysis versus beta-lactam cleavage.

EstB from Burkholderia gladioli: a novel esterase with a beta-lactamase fold reveals steric factors to discriminate between esterolytic and beta-lactam cleaving activity

A novel esterase from Burkholderia gladioli which shows high deacetylation activity on cephalosporins is related to β-lactamases and dd-peptidases

A new series of materials of the glaserite family with the general formula K3RE(VO4)2(RE = Sc, Y, Dy, Ho, Er, Tm, Yb, and Lu) have been hydrothermally synthesized using 10 M K2CO3 at 560 °C and characterized by single crystal X-ray diffraction (XRD), powder XRD, differential thermal analysis/thermogravimetric analysis (DTA/TGA), energy-dispersion X-ray (EDX), Raman, infrared, and absorption spectroscopy. All the compounds crystallize in the trigonal P3m1 space group (No. 164), and their structures contain VO4 tetrahedra, REO6 octahedra, and two different K(1)O10 and K(2)O12 polyhedra. The spectroscopic properties of Nd3+, Yb3+, or Er3+ doped K3RE(VO4)2 (RE = Y or Lu) are also reported, and the results obtained show that these compounds have promising potential as new laser host materials.

Hydrothermal Synthesis and Spectroscopic Properties of a New Glaserite Material, K3RE(VO4)2 (RE = Sc, Y, Dy, Ho, Er, Yb, Lu, or Tm) with Potential Lasing and Optical Properties

Detection of a new enzyme for stereoselective hydrolysis of linalyl acetate using simple plate assays for the characterization of cloned esterases from Burkholderia gladioli.

Crystals of the esterase EstB were obtained at 277 K with the hanging-drop technique from polyethylene glycol 4000 solutions containing 2-propanol at pH 7.5. The crystals belong to the trigonal space group P3(1)21 (or P3(2)21) with cell dimensions a = b = 82.9 and c = 193.4 A (at 100 K). The crystals diffract beyond a resolution of 2.0 A.

Crystallization and preliminary x-ray diffraction studies of the Pseudomonas marginata esterase EstB

The two new esterases, EP6 and EP10, from Pseudomonas marginata were studied with respect to their substrate specificities and selectivities. Esters of aliphatic and cyclic secondary alcohols were shown to be substrates for EP10, which could be accepted stereoselectively in hydrolysis and transesterification reactions. EP6 showed no selectivity in hydrolysis of the studied substrates.

New Pseudomonas esterases by genetic engineering

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Crystallization and preliminary x-ray diffraction studies of the Pseudomonas marginata esterase EstB

New Pseudomonas esterases by genetic engineering