2,6-Hepta-O-tert-butyldimethylsilyl α-cyclodextrin - A carbohydrate undecaol with all OH groups visible in NMR indicative of a partially disrupted hydrogen bond network.

During a synthesis of the well-known and useful building block 6-hexa-O-tert-butyldimethylsilyl α-cyclodextrin (2) by silylation of α-cyclodextrin (1) we isolated as a byproduct the oversilylated 2,6-hepta-O-tert-butyldimethylsilyl α-cyclodextrin (3) where one 2-OH group has also been silylated. This unsymmetrical new compound has a remarkable H NMR spectrum in CDCl where all 11 alcohol groups are visible. We have analyzed the spectrum of 3 using 1D and 2D 800 MHz NMR and are able to assign all the 11 alcohol protons.

Synthesis of -glycoside analogues of isopropyl β-D-1-thiogalactopyranoside (IPTG) and 1-β-D-galactopyranosyl-2-methylpropane. Conformational analysis and evaluation as inhibitors of the lac repressor in and as galactosidase inhibitors.

Isopropyl 1-thio-β-D-galactopyranoside (IPTG, 1) is used widely as an inducer of protein expression in and 1-β-D-galactopyranosyl-2-methylpropane (2), a -glycoside analogue of 1, has also been identified as an inducer. Here, synthesis and study of mimetics of 1 and 2, 1-β-D-galactopyranosyl-2-methylpropan-1-ols and two cyclic acetals derivatives, that constrain the presentation of the iPr group in various geometries is described. Conformational analysis of -glycosides in protic solvent is performed using (i) Desmond metadynamics simulations (OPLS4) and (ii) use of values obtained by H-NMR spectroscopy.

New methods of modification of α-cyclodextrin.

While being some of the oldest supramolecular hosts, cyclodextrins remain very popular as molecular binders in materials, devices, artificial enzymes and more. The popularity is undoubtedly connected to the ready availability, carbohydrate biomass origin, biodegradability and water solubility of the cyclodextrins. Many of these applications require synthetic modification of the cyclodextrin - at the simplest the attachment of a linker - but also often attachment of several functional groups, lids, bridges .

Spectroscopic Investigation of the Role of Water in Copper Zeolite Methane Oxidation.

Methane is one of the most potent greenhouse gases; developing technology for its abatement is essential for combating climate change. Copper zeolites can activate methane at low temperatures and pressures, demonstrating promise for this technology. However, a barrier to industrial implementation is the inability to recycle the Cu(II) active site.

UV-Vis-NIR Absorption Spectroscopy and Catalysis.

This review highlights UV-vis-NIR range absorption spectroscopy in catalysis. A variety of experimental techniques identifying reaction mechanisms, kinetics, and structural properties are discussed. Stopped flow techniques, use of laser pulses, and use of experimental perturbations are demonstrated for studies of enzymatic, homogeneous, heterogeneous, and photocatalysis.

One-step synthesis of Ling's tetrol and its conversion into A,D-di--α-cyclodextrin derivatives.

2,3,6-Tetradeca--benzyl-α-cyclodextrin or Ling's tetrol is a unique α-cyclodextrin derivative that is partially protected with specific access points on both rims of the cyclodextrin structure. Ling's tetrol is therefore potentially useful for the synthesis of more complex and sophisticated enzyme models and supramolecular structures. However, the original synthesis gave only 10% yield after a reaction time of 4 days, and a recent improvement that gave 52% yield required two steps and a reaction time in one step of 6 days.

CO complexation with cyclodextrins.

Carbon dioxide (CO) emissions from industrial processes, power generation, and transportation contribute significantly to global warming and climate change. Carbon capture and storage (CCS) technologies are essential to reduce these emissions and mitigate the effects of climate change. Cyclodextrins (CDs), cyclic oligosaccharides, are studied as potential CO capture agents due to their unique molecular structures and high selectivity towards CO.

Tuning Copper Active Site Composition in Cu-MOR through Co-Cation Modification for Methane Activation.

The industrial implementation of a direct methane to methanol process would lead to environmental and economic benefits. Copper zeolites successfully execute this reaction at relatively low temperatures, and mordenite zeolites in particular enable high methanol production. When loaded to a Cu/Al ratio of 0.

A study of the DIBAL-promoted selective debenzylation of α-cyclodextrin protected with two different benzyl groups.

An α-cyclodextrin protected with 2,4-dichlorobenzyl groups on the primary alcohols and ordinary benzyl groups on the secondary alcohols was prepared and subjected to DIBAL (diisobutylaluminum hydride)-promoted selective debenzylation. Debenzylation proceeded by first removing two dichlorobenzyl groups from the 6 positions and then removing one or two benzyl groups from the 3 positions.

Methane Activation by a Mononuclear Copper Active Site in the Zeolite Mordenite: Effect of Metal Nuclearity on Reactivity.

The direct conversion of methane to methanol would have a wide reaching environmental and industrial impact. Copper-containing zeolites can perform this reaction at low temperatures and pressures at a previously defined O-activated [CuO] site. However, after autoreduction of the copper-containing zeolite mordenite and removal of the [CuO] active site, the zeolite is still methane reactive.

Taming of the DIBAL Promoted Debenzylation of α-Cyclodextrin. Kinetics, Substituent Effects and Efficient Synthesis of Lings Tetrol.

The kinetics of the reaction of perbenzyl α-cyclodextrin was studied varying the concentration of DIBAL and substrate, and the temperature. The initial debenzylation was found to be 1 order in substrate and follow the relationship 0.0675+0.

Second-Sphere Lattice Effects in Copper and Iron Zeolite Catalysis.

Transition-metal-exchanged zeolites perform remarkable chemical reactions from low-temperature methane to methanol oxidation to selective reduction of NOx pollutants. As with metalloenzymes, metallozeolites have impressive reactivities that are controlled in part by interactions outside the immediate coordination sphere. These second-sphere effects include activating a metal site through enforcing an "entatic" state, controlling binding and access to the metal site with pockets and channels, and directing radical rebound vs cage escape.

Selective Formation of α-Fe(II) Sites on Fe-Zeolites through One-Pot Synthesis.

α-Fe(II) active sites in iron zeolites catalyze NO decomposition and form highly reactive α-O that selectively oxidizes unreactive hydrocarbons, such as methane. How these α-Fe(II) sites are formed remains unclear. Here different methods of iron introduction into zeolites are compared to derive the limiting factors of Fe speciation to α-Fe(II).

Cage effects control the mechanism of methane hydroxylation in zeolites.

Catalytic conversion of methane to methanol remains an economically tantalizing but fundamentally challenging goal. Current technologies based on zeolites deactivate too rapidly for practical application. We found that similar active sites hosted in different zeolite lattices can exhibit markedly different reactivity with methane, depending on the size of the zeolite pore apertures.

Spectroscopic Definition of a Highly Reactive Site in Cu-CHA for Selective Methane Oxidation: Tuning a Mono-μ-Oxo Dicopper(II) Active Site for Reactivity.

Using UV-vis and resonance Raman spectroscopy, we identify a [CuO] active site in O and NO activated Cu-CHA that reacts with methane to form methanol at low temperature. The Cu-O-Cu angle (120°) is smaller than that for the [CuO] core on Cu-MFI (140°), and its coordination geometry to the zeolite lattice is different. Site-selective kinetics obtained by operando UV-vis show that the [CuO] core on Cu-CHA is more reactive than the [CuO] site in Cu-MFI.

Attachment of cyclodextrin acids to PEGA resin and study of binding with fluorescence microscopy.

Three different cyclodextrin acids, 6,6-di-O-(prop-2-carboxy-1,3-dienyl)-α-cyclodextrin (1), 6-deoxy-β-cyclodextrin-6-carboxylic acid (2), 6-deoxy-β-cyclodextrin-6-ethylenecarboxylic acid (3), were prepared and attached to amino PEGA resin as amides using coupling conditions with COMU and NEM. Host-guest binding to the resins was studied by fluorescence microscopy using 8-anilinoaphtalene-1-sulfonic acid (ANS) as guest, and was found to follow the equation I = I*[ANS]/([ANS] + K) where F, F and K are the fluorescence, maximum fluorescence and K the dissociation constant for the ANS-cyclodextrin complex, respectively. K was 4.

Advances in the synthesis, characterisation, and mechanistic understanding of active sites in Fe-zeolites for redox catalysts.

The recent research developments on the active sites in Fe-zeolites for redox catalysis are discussed. Building on the characterisation of the α-Fe/α-O active sites in the beta and chabazite zeolites, we demonstrate a bottom-up approach to successfully understand and develop Fe-zeolite catalysts. We use the room temperature benzene to phenol reaction as a relevant example.

Imino- and Azasugar Protonation Inside Human Acid β-Glucosidase, the Enzyme that is Defective in Gaucher Disease.

Gaucher disease is caused by mutations in human acid β-glucosidase or glucocerebrosidase (GCase), the enzyme responsible for hydrolysis of glucosyl ceramide in the lysosomes. Imino- and azasugars such as 1-deoxynojirimycin and isofagomine are strong inhibitors of the enzyme and are of interest in pharmacological chaperone therapy of the disease. Despite several crystal structures of the enzyme with the imino- and azasugars bound in the active site having been resolved, the actual acid-base chemistry of the binding is not known.

Synthesis of Shld Derivatives, Their Binding to the Destabilizing Domain, and Influence on Protein Accumulation in Transgenic Plants.

A series of 35 analogues of Shld with modifications in the A-residue and the C-residues were prepared and investigated for binding to FKBP and GFP accumulation in transgenic plants. The modifications investigated explored variations that were supposedly inside or outside the receptor binding site with the latter being important by influencing the overall polarity of the compounds in order to improve the absorption in plants. The binding of the new compounds to the destabilizing domain was determined using a fluorescence polarization competition assay, and the GFP expression in engineered Arabidopsis thaliana was studied.

Mechanism of selective benzene hydroxylation catalyzed by iron-containing zeolites.

A direct, catalytic conversion of benzene to phenol would have wide-reaching economic impacts. Fe zeolites exhibit a remarkable combination of high activity and selectivity in this conversion, leading to their past implementation at the pilot plant level. There were, however, issues related to catalyst deactivation for this process.

Spectroscopic Identification of the α-Fe/α-O Active Site in Fe-CHA Zeolite for the Low-Temperature Activation of the Methane C-H Bond.

The formation of single-site α-Fe in the CHA zeolite topology is demonstrated. The site is shown to be active in oxygen atom abstraction from NO to form a highly reactive α-O, capable of methane activation at room temperature to form methanol. The methanol product can subsequently be desorbed by online steaming at 200 °C.

An Inexpensive and Scalable Synthesis of Shld.

A synthesis of the important FKBP ligand Shld is reported. The synthesis avoids stoichiometric use of expensive and chiral reagents, maintains enantioselectivity and provides a high overall yield (39%). The main features in the method are enantioselective alkylation for preparation of the phenyl acetic acid moiety (building block A), catalytic enantioselective reduction for obtaining the chiral diaryl-1-propanol (building block C), and direct acylation of S-pipecolic tartrate rather than use of expensive Fmoc-pipecolic acid.

Structural characterization of a non-heme iron active site in zeolites that hydroxylates methane.

Iron-containing zeolites exhibit unprecedented reactivity in the low-temperature hydroxylation of methane to form methanol. Reactivity occurs at a mononuclear ferrous active site, α-Fe(II), that is activated by NO to form the reactive intermediate α-O. This has been defined as an Fe(IV)=O species.