We developed an experimentally simple method for localized N-tert-butyloxycarbonyl amino group (N-Boc) deprotection on surface applicable to meso-scale on-demand patterning for further synthetic ...modifications. The chemical patterning is accomplished on heated self-assembled monolayers using micro-drop equipment and water as the sole chemical.
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In this work, we mainly investigate the adsorption properties of the simulated single and mixture wastewaters over porous Bi2MoO6@BiOCl@MOF-199 (BMO@BOC@MOF-199), including methylene blue (MB), ...rhodamine blue (RhB), methyl orange (MO) and chromium (VI). It is found that BMO@BOC@MOF-199 has a high adsorption capacity for MB, but a poor adsorption capacity for MO. Specifically, for single MB solution, 67%, 80% and 96% of MB are adsorbed by BMO@BOC, MOF-199 and BMO@BOC@MOF-199, respectively. The higher adsorption capacity of BMO@BOC@MOF-199 could be due to its higher surface area and larger pore volume. For single MO solution, nevertheless, only 16%, 13% and 7% of MO are adsorbed by BMO@BOC, MOF-199 and BMO@BOC@MOF-199, respectively. The different adsorption efficiency for MB and MO could be relative to their different molecular structures, which have different electrostatic interactions with adsorbent surface. For single RhB and single Cr(VI) solution, BMO@BOC@MOF-199 has adsorbed 30% RhB and 10% Cr(VI). In RhB-MO mixture solution, 32% RhB and 9% MO can be adsorbed by BMO@BOC@MOF-199, while in Cr(VI)–RhB-MO mixture solution, 7% Cr(VI), 3% RhB and 42% MO can be adsorbed by BMO@BOC@MOF-199. It is seen that in RhB-MO mixture solution, the adsorption efficiencies of RhB and MO by BMO@BOC@MOF-199 do not obviously change as compared to single RhB and single MO solution, while in Cr(VI)–RhB-MO mixture solution, the adsorption efficiency of MO has increased by 5 times, compared to single MO solution; but the adsorption efficiency of RhB has decreased by 9.7 times as compared to single RhB solution, and the adsorption efficiency of Cr(VI) has decreased slightly, compared to single Cr(VI) solution. The results are mainly attributed to the competitive adsorption on the adsorbent surface. This work can help us to understand the adsorption process for practical wastewater.
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•Bi2MoO6@BiOCl@MOF-199 is got via a one-pot solvothermal method.•BMO@BOC@MOF-199 shows a higher adsorption capacity for MB than MO.•All adsorption process follows the nonlinear pseudo-first and pseudo second order kinetics.•This research work favors to understand adsorption processes for practical wastewater.
Thermal N-Boc deprotection of a range of amines is readily effected in continuous flow, in the absence of an acid catalyst. While the optimum results were obtained in methanol or trifluoroethanol, ...deprotection can be effected in a range of solvents of different polarities. Sequential selective deprotection of N-Boc groups has been demonstrated through temperature control, as exemplified by effective removal of an aryl N-Boc group in the presence of an alkyl N-Boc group. As a proof of principle, a telescoped sequence involving selective deprotection of an aryl N-Boc group from 9h followed by benzoylation and deprotection of the remaining alkyl N-Boc group to form amide 13 proved successful.
Novel Sn doped BiOCl nanosheets with typical conversion pathways of photocatalytic toluene degradation were constructed by a facile method at room temperature.
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•Novel BOC-Sn was ...fabricated by a one-step chemical precipitate method.•BOC-Sn exhibits significantly enhanced photocatalytic activity.•BOC-Sn exhibits typical conversion mechanism of photocatalytic degradation toluene.
The Sn doped BiOCl (BOC-Sn) nanosheets photocatalyst was fabricated by a one-step chemical precipitate method using BiCl3 and SnCl4·5H2O as precursors. The as-fabricated BOC-Sn was applied to the photocatalytic purification of toluene. The microstructures and physicochemical properties of the samples were systematically characterized by XRD, SEM, TEM, UV–vis DRS, PL, XPS, EPR, photocurrent, EIS, BET-BJH. The in situ FT-IR spectroscopy was used to investigate the adsorption and reaction intermediates of photocatalytic toluene degradation under ultraviolet light irradiation. The photocatalytic reaction mechanism was proposed based on the DFT calculation and ESR results. The results indicate that the doped Sn atoms could promote the light absorption, separation and migration of photo-generated carriers on BOC-Sn. However, the reaction intermediates were benzyl alcohol, benzaldehyde and benzoic acid during the photocatalytic toluene degradation on BOC-Sn, which revealed that BOC-Sn and BOC samples featured different reaction mechanisms. The present work could provide insight into the designed Sn-doped BiOCl nanosheets and photocatalytic toluene degradation mechanisms.
Chemical synthesis of proteins bearing base‐labile post‐translational modifications (PTMs) is a challenging task. For instance, O‐acetylation and S‐palmitoylation PTMs cannot survive Fmoc removal ...conditions during Fmoc‐solid phase peptide synthesis (SPPS). In this work, we developed a new Boc‐SPPS‐based strategy for the synthesis of peptide C‐terminal salicylaldehyde (SAL) esters, which are the key reaction partner in Ser/Thr ligation and Cys/Pen ligation. The strategy utilized the semicarbazone‐modified aminomethyl (AM) resin, which could support the Boc‐SPPS and release the peptide SAL ester upon treatment with TFA/H2O and pyruvic acid. The non‐oxidative aldehyde regeneration was fully compatible with all the canonical amino acids. Armed with this strategy, we finished the syntheses of the O‐acetylated protein histone H3(S10ac, T22ac) and the hydrophobic S‐palmitoylated peptide derived from caveolin‐1.
A Boc‐SPPS based method towards the synthesis of peptide C‐terminal salicylaldehyde esters compatible with all canonical amino acids was developed. The method could facilitate the synthesis of proteins bearing base‐labile post‐translational modifications, e.g., O‐acetylation and S‐palmitoylation.
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•Carbamates yield other carbamates or amidinoureas without using strong base/catalyst.•Boc/Cbz/Fmoc-protected guanidines react with aliphatic amines to yield amidinoureas.•Protected ...guanidines react with alcohols interchanging Boc by Cbz & Fmoc/Cbz by Boc.•Boc-protected aniline did not react with alcohols or amines under the conditions used.
The reactivity of carbamates to produce other carbamates (by reaction with alcohols) or amidinoureas (by reaction with amines), without the use of strong bases or catalysts, has been studied indicating the suitability/selectivity of the method in achieving differently substituted/protected guanidines. Thus, 4-(4-guanidinophenyloxy)anilines fully protected with the most common amino protecting groups on the guanidino moiety (Boc, Cbz and Fmoc) and Boc-protected on the anilino functionality have been used as starting materials. Reactions with aliphatic amines yielded mono-substitution of one of the guanidino protecting groups producing the corresponding amidinoureas. Reactions with alcohols resulted in the corresponding substitution of both guanidino protecting groups allowing for the interchange of Boc by Cbz and Fmoc and Cbz by Boc. The Boc-protected aniline did not undergo any reaction under the conditions used.
Organic solvent separations are energy intensive yet ubiquitous unit operations in the chemical, petrochemical, and pharmaceutical industries. Membrane technology can significantly reduce the demands ...for energy, carbon, and water in these operations. However, the separation of similar molecules is often required, which is a difficult challenge for membranes. Some polymers used in organic solvent reverse osmosis (OSRO) have been known to suffer from plasticization and dilation, making them inefficient for these molecular separations. Here we describe a method to address this problem by uniformly crosslinking a selective layer of a thin film composite (TFC) membrane to improve stability in organic solvents and tune separation performance. Crosslinking agents hexamethylene diamine, p-xylylene diamine, and 4,4′-biphenyldicarbontrile diamine, protected as N-tert-butyloxycarbonyl (Boc) carbamates, were introduced to the commercial polymer Matrimid® 5218. Boc protection rendered them sufficiently soluble in the polymer matrix to obviate costly liquid-phase crosslinker infusion steps. After casting, the amines within the membrane were thermally deprotected to induce a solid-state crosslinking reaction. The resulting crosslinked TFC membranes showed excellent stability in organic solvents, separation performance with binary (toluene/triisopropylbenzene) and 9-component organic solvent mixtures, and tunable separation characteristics based on the nature and concentration of the crosslinking agent.
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•New method to solubilize crosslinking agents for uniform reaction.•Improved stability of polyimide in organic solvents.•Substantial improvement in small-molecule separations performance.
N…N pnicogen bonds in Boc-DOPA-OMe Tripathi, Garima; Badi-uz-zama, Khalid; Ramanathan, Gurunath
Chemical physics letters,
06/2016, Letnik:
653
Journal Article
Recenzirano
Crystal structures of Boc-DOPA-OMe in racemic (rac) and homochiral (S, chi) form were determined. Pnicogen bonds were observed in both forms, bifurcating the 10-membered ring, supported by ...theoretical studies. Display omitted
•Crystal structures of Boc-DOPA-OMe in racemic and homochiral (S) form were determined.•Presence of N…N pnicogen interaction is seen in crystals of both forms and supported by QTAIM calculations.•Determination of stabilization energies of these interactions.
Crystal structures of Boc-DOPA-OMe in racemic and homochiral (S) form were determined and found to be similar in terms of supramolecular organization. The computation of electron density and its topological analysis provided insight into the interactions of the molecules within their crystal environments. The presence of N…N pnicogen bonds in both crystals was also predicted by QTAIM calculations, which are reported for the first time in amino acid systems.
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•The ZWIX(+) column allowed getting the Boc-Aph(Hor)-OH (1) isomeric peaks resolved.•ECD studies and molecular dynamic simulations allowed to assign the elution order.•Molecular ...descriptors revealed the active role of achiral elements of the CSP.
A chiral chromatography method enabling the simultaneous diastereo- and enantioseparation of Nα-Boc-N4-(hydroorotyl)-4-aminophenylalanine Boc-Aph(Hor)-OH, 1 was optimized with a quinine-based zwitterionic stationary phase. The polar-ionic eluent system consisting of ACN:MeOH:water—49.7:49.7:0.6 (v/v/v) with formic acid (4.0mM) and diethylamine (2.5mM), allowed the successful separation of the four acid stereoisomers: αd,d-/d,l-1=1.08; αd,l-/l,d-1=1.08; αl,d-/l,l-1=1.40.
According to the in-house developed synthetic procedure and the recorded electronic circular dichroism spectra, the following stereoisomeric elution order was readily established in the optimal chromatographic conditions: d,d-1<d,l-1<l,d-1<l,l-1.
With the aim of better understanding the molecular basis of the retention behaviour of the four stereoisomers in the employed chromatographic system and conditions, a computational protocol consisting in molecular dynamics simulations was applied. The use of the three descriptors INTER (in kcalmol−1, encoding for the interaction energy between the selector SO unit and the whole system), INTER_SA (in kcalmol−1, encoding for the interaction energy between SO and the sole selectand SA), and SELF (in kcalmol−1, encoding for the conformational energy of SA relative to its minimum energy registered by the collected snapshots) revealed the active role of achiral sub-structural elements of the chiral stationary phase and eluent components in the overall stereorecognition mechanism.
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