Trifluoroacetic Acid In Dichloromethane Research Articles

Waste treats waste: Facile fabrication of porous adsorbents from recycled PET and sodium alginate for efficient dye removal

Dye-contaminated water and waste plastic both pose enormous threats to human health and the ecological environment, and simultaneously solving these two issues in a sustainable and resource-saving way is highly important. In this work, a sodium alginate-polyethylene terephthalate-sodium alginate (SA@PET) composite adsorbent for efficient dye removal is fabricated using wasted PET bottle and marine plant-based SA via simple and energy-efficient nonsolvent-induced phase separation (NIPS) method. Benefiting from its porous structure and the abundant binding sites, SA@PET shows an excellent methylene blue (MB) adsorption capacity of 1081 mg g−1. The Redlich–Peterson model more accurately describes the adsorption behavior, suggesting multiple adsorption mechanisms. In addition to the electrostatic attractions of SA to MB, polar interactions between the PET matrix and MB are also identified as adsorption mechanisms. It is worth mentioning that SA@PET could be recycled 7 times without a serious decrease in performance, and the trifluoroacetic acid-dichloromethane solvent involved in the NIPS process has the possibility of reuse and stepwise recovery. Finally, the discarded adsorbent could be completely degraded under mild conditions. This work provides not only a composite adsorbent with excellent cationic dye removal performance for wastewater treatment, but also an upcycling strategy for waste PET.

Calix[3]Pyrrole and Related Macrocycles: Synthesis and Properties

Calix[4]pyrrole is a porphyrinogen-like macrocycle in which four pyrrole units are linked by four sp3-hybridized carbon atoms at the α-positions. While such tetrapyrrolic macrocycles are readily synthesized by acid-catalyzed condensation reactions of pyrrole monomer and carbonyl compound, analogous macrocycles composed of three pyrrole units are always not observed. Calix[3]pyrrole is a ring-contracted analogue of calix[4]pyrrole, and has been missing in porphyrin-related chemistry. In this presentation, the first synthesis of calix[3]pyrrole and its furan-embedded analogues is reported, and their unique reactivity derived from their macrocyclic ring strain will be discussed.Synthesis of calix[3]pyrrole started with a linear trimer of 3,3-dimethylpentane-2,5-dione. Intramolecular cyclization of the linear hexaketone was accomplished in 5 steps to give a cyclic hexaketone precursor. Paal–Knorr type pyrrole formation reaction of cyclic hexaketone gave calix[3]pyrrole in 41% yield (Scheme 1). Using similar strategies, analogous calix[3]-type macrocycles, namely, calix[1]furan[2]pyrrole, calix[2]furan[1]pyrrole, and calix[3]furan, were successfully synthesized. Single crystal X-ray diffraction analysis of calix[3]pyrrole revealed its strained structure, and the theoretical calculations showed the strain energy of calix[3]pyrrole is 22.1 kcal/mol per unit higher than that of calix[4]pyrrole. Such strain energy tends to decrease as the number of pyrrole unit decreased.Calix[3]pyrrole exhibited unique reactivity derived from macrocyclic ring strain under acidic (Rothemund–Lindsey) conditions that are frequently used for porphyrin synthesis. When calix[3]pyrrole was dissolved in 10 mM solution of trifluoroacetic acid in dichloromethane, calix[6]pyrrole was quantitatively formed within 30 seconds (Scheme 1). Similar strain-induced ring expansion was observed for calix[1]furan[2]pyrrole, but full conversion took approximately 5 minutes. On the other hand, calix[2]furan[1]pyrrole and calix[3]furan did not show ring expansion. Detailed mechanistic analysis revealed that protonation at a pyrrole unit in calix[3]pyrrole triggers irreversible ring-cleavage to give a linear tripyrrane moiety which undergoes cyclodimerization under acidic conditions.The strain-induced ring expansion reaction of calix[3]pyrrole solved a long-standing question in porphyrin-related chemistry. Tripyrrolic macrocycles such as calix[3]pyrrole are, even formed, not isolable from pyrrole condensation reaction using acid, because the strain-induced conversion to calix[6]pyrrole is too fast. Besides, this reaction provided a novel approach to ring-expanded calix-type macrocycles. Figure 1

Effect of protonation on the spectral properties of subphthalocyanine and tripyrazinosubporphyrazine

Using well-known methodology perfluorinated sybphthalocyanine (F12 sPcBCl) and hexaphenyltripyrazinosubporphyrazine (Ph6Pyz3sPzBCl) were obtained and further its spectral and base properties have been studied by spectrophotometric titration and fluorescence spectroscopy. By means of spectrophotometric titration sequential protonation of two azomethine bridges was observed with the shifts of the absorption Q bands to 625-665 nm (for F12 sPcBCl), to 584-683 nm and CT (charge transfer) band to 426-453 nm (for Ph6Pyz3sPzBCl). The spectral changes in the electronic absorption spectra of F12sPcBCl observed in an acid medium differ significantly compared to Ph6Pyz3sPzBCl. Protonation of Ph6Pyz3sPzBCl was observed in 0.08-0.35 M solution of trifluoroacetic acid in dichloromethane, in contrast to F12 sPcBCl for which protonation in dichloromethane was observed at TFA concentration equal to 1.34 M. Bathochromic shift of the Q bands in the emission spectra was indicated for each of the protonated forms of the compounds, accompanied by a decrease in the fluorescence intensity with increasing acidity.

SYNTHESIS AND PROPERTIES OF NEW N-ACYL DERIVATIVES OF ANTHRANILIC ACID

A series of N-acyl derivatives of anthranil (or o -aminobenzoic acid) was first synthesized, namely 2-(4-octylbenzamido)benzoic acid, 2-(4-(heptyloxy)- benzamido)benzoic acid, 2-(4-(heptylsulfanyl)benz-amido)benzoic acid. 2-(4-octylbenzamido)benzoic acid was synthesized in five stages of octylbenzene, by acylating chloride acid using a Friedie-Crafts reaction. 2-(4-(heptyloxy)benzamido)benzoic acid was prepared from the methyl ester of p-hydroxybenzoic acid which, at the first stage, was activated with 1-bromoheptane in acetonitrile with potassium carbonate and catalytic amount of sodium iodide at heating. After that, hydrolysis of the ester group by hydroxide in the methanol–water system was performed. Synthesis of 2-(4-(heptylsulfanyl)benzamido)benzoic acid was carried out from p-sulfanylbenzoic acid, which was activated with 1-bromoheptane, in a system of ethanol–water with sodium hydroxide. Chlorinated hydrides of acids were obtained by reaction of acids with chlorinated thionyl in benzene. Acylation of the tret-butyl ester of anthranilic acid with formed chlorohydrides was carried out in pyridine upon heating and in dichloromethane with triethylamine (as the base), and dimethylaminopyridine (catalyst).At the last stage of the synthesis of all derivatives, the hydrolysis of tret-butyl esters with trifluoroacetic acid in dichloromethane to the formation of terminal compounds took place.The composition and structure of the synthesized compounds were determined using NMR 1H, infrared spectroscopy. The shape and position of the bands in the IR absorption spectra of the synthesized anthranilic acid derivatives are shifted and splited in comparison with the parent acid due to the presence of a secondary amino group, an additional aromatic moiety, and a different nature of the substitutes in the para-position to the amino group. For all synthesized derivatives, the sensitivity of various morphological forms Candida albicans was determined. The influence of the test substances on the cells of the yeast fungus was determined for 24–48 hours using Saburo and Spider nutrient media with the addition of mannitol. Compared with the already known influence of anthranilic acid on Candida albicans cells grown in Saburo nutrient medium for 24 hours, the compounds studied were more effective at all stages of cultivation. It has been shown that the synthetic derivatives studied are more active with respect to the cells in the biofilm composition, which consists of the yeast-like form of Candida albicans, than those cells that form a hyphal type biofilm. The yeast-like form of the Candida albicans cell is susceptible to synthetic derivatives. It is shown that the level of sensitivity of compounds 1-3 is higher in 4-6 times compared with anthranilic acid. Glyphs have been found to be more susceptible to the effects of the compounds studied than Е yeast cells of Candida albicans

Solid-Phase Synthesis of 1,3,4-Thiadiazole Derivatives via Desulfurative Cyclization of Thiosemicarbazide Intermediate Resin.

A 1,3,4-thiadiazole library was constructed by solid-phase organic synthesis. The key step of this solid-phase synthesis involves the preparation of polymer-bound 2-amido-5-amino-1,3,4-thiadiazole resin by the cyclization of thiosemicarbazide resin using p-TsCl as the desulfurative agent, followed by the functionalization of the resin by alkylation, acylation, alkylation/acylation, and Suzuki coupling reactions. Both the alkylation and acylation reactions chemoselectively occurred at the 2-amide position of 2-amido-5-amino-1,3,4-thiadiazole resin and the 5-amine position of 2-amido-5-amino-1,3,4-thiadiazole resin, respectively. Finally, these functionalized 1,3,4-thiadiazole resins were treated with trifluoroacetic acid in dichloromethane, affording diverse 1,3,4-thiadiazole analogs in high yields and purities. The 1,3,4-thiadiazole analogs show a different distribution of physicochemical and biological properties compared with our previously constructed 1,3,4-oxadiazole and 1,3,4-thiadiazole libraries in a range of orally available drug properties.

Formation of Ground State Triplet Diradicals from Annulated Rosarin Derivatives by Triprotonation.

Annulated rosarins, β,β'-bridged hexaphyrin(1.0.1.0.1.0) derivatives 1-3, are formally 24 π-electron antiaromatic species. At low temperature, rosarins 2 and 3 are readily triprotonated in the presence of trifluoroacetic acid in dichloromethane to produce ground state triplet diradicals, as inferred from electron paramagnetic resonance (EPR) spectral studies. From an analysis of the fine structure in the EPR spectrum of triprotonated rosarin H₃3(3+), a distance of 3.6 Å between the two unpaired electrons was estimated. The temperature dependence of the singlet-triplet equilibrium was determined by means of an EPR titration. Support for these experimental findings came from calculations carried out at the (U)B3LYP/6-31G* level, which served to predict a very low-lying triplet state for the triprotonated form of a simplified model system 1.

Redox Properties and Catalytic Ability toward Electrochemical Proton Reduction of Sulfur-Bridged Trinuclear Mo3S4 Complexes Containing Acetate, Trifluoroacetate, and/or Dithiophosphate as Bridging Ligands

Abstract A novel complex with the terminal acetonitrile and bridging trifluoroacetate (tfa) ligands of [Mo3S4(dtp)3(μ-tfa)(NCCH3)] (dtp: diethyl dithiophospate) (1-tfa) was prepared from the substitution reaction of [Mo3S4(dtp)3(μ-dtp)(NCCH3)] (1-dtp) with trifluoroacetate anhydride in acetonitrile. The reaction of 1-dtp with trifluoroacetic acid in dichloromethane also afforded 1-tfa. Complex 1-tfa reacts with pyridine in ethanol resulting in the formation of a complex with the terminal pyridine ligand (py), [Mo3S4(dtp)3(μ-tfa)(py)] (2-tfa). Structures of 1-tfa and 2-tfa were determined by single-crystal X-ray structural analysis showing that one of three Mo–Mo distances depend on a kind of the bridging ligands, dtp, OAc, and tfa, while no trends in the other two Mo–Mo distances in each of the complexes with the different bridging ligands. Each of the cyclic voltammograms of 1-dtp, [Mo3S4(dtp)3(μ-OAc)(NCCH3)] (OAc: acetate) (1-OAc), 1-tfa, [Mo3S4(dtp)3(μ-OAc)(py)] (2-OAc), and 2-tfa showed two consecutive one-electron reduction waves and an oxidation wave, which are formally assigned to the Mo(IV IV IV)/Mo(III IV IV), Mo(III IV IV)/Mo(III III IV), and Mo(V IV IV)/Mo(IV IV IV) couples, respectively. The re-oxidation and re-reduction peaks for the second reduction and the oxidation processes were not observed for all of the complexes. The redox potentials of the first reduction processes were shifted up to ca. 200 mV with the bridging and terminal ligands, for example, the redox potentials appeared at −0.98 and −1.19 V vs. Fc/Fc+2-OAc and 1-tfa, respectively, due to the lower electron-donating ability of CH3CN and tfa ligands compared to that of the py and OAc ligands. The re-oxidation peak for the second reduction process of 2-OAc was observed at −80 °C suggesting that this is an EC process and the chemical reaction following the second electrochemical reduction is probably inhibited at low temperature. On the other hand, no re-reduction peak for the oxidation process appeared even at −80 °C implying that the oxidation process is accompanied by a significant structural change. This argument is supported by the results of the DFT calculation. The HOMO component of the complex contains a bonding character between the two acetate-bridged Mo centers and the other acetate-unbridged one, and the spin densities of the 1-electron oxidized complex mostly located at the one of two acetate-bridged Mo centers and the other acetate-unbridged one. Cyclic voltammograms of these complexes in the presence of trifluoroacetic acid as a proton source exhibited catalytic currents around the first reduction wave for each complex. The DFT calculations for 2-OAc and 2-tfa demonstrated that the HOMO components are also distributed over the doubly bridged sulfur ligands in addition to the Mo centers in the Mo3S4 core. These result suggests that a protonation reaction of 2-OAc and 2-tfa probably occurs on the doubly bridged sulfur ligand in the Mo3S4 core.

Elaboration of the carbocyclic ring systems in plumarellide and rameswaralide using a coordinated intramolecular cycloaddition approach, based on a common biosynthesis model

Treatment of the furanbutenolide 18a with trifluoroacetic acid in dichloromethane results in hydrolysis and rearrangement leading to the cycloheptene ring-containing system 19a found in rameswaralide (5). Similar treatment of the diastereoisomeric furanbutenolide 17 produces the cyclohexene ring-containing system 23 present in plumarellide (1), together with the C-7 epimer 24 of 19a. The acid-catalysed conversions 18a→19a and 17→23 are rationalised implicating [6+4] and [4+2] cycloaddition pathways and/or two-step carbocation cyclisation sequences.

Synthesis and application of Nα‐Fmoc‐Nπ‐4‐methoxybenzyloxymethylhistidine in solid phase peptide synthesis

The 4-methoxybenzyloxymethyl (MBom) group was introduced at the Nπ-position of the histidine (His) residue by using a regioselective procedure, and its utility was examined under standard conditions used for the conventional and the microwave (MW)-assisted solid phase peptide synthesis (SPPS) with 9-fluorenylmethyoxycarbonyl (Fmoc) chemistry. The Nπ-MBom group fulfilling the requirements for the Fmoc strategy was found to prevent side-chain-induced racemization during incorporation of the His residue even in the case of MW-assisted SPPS performed at a high temperature. In particular, the MBom group proved to be a suitable protecting group for the convergent synthesis because it remains attached to the imidazole ring during detachment of the protected His-containing peptide segments from acid-sensitive linkers by treatment with a weak acid such as 1% trifluoroacetic acid in dichloromethane. We also demonstrated the facile synthesis of Fmoc-His(π-MBom)-OH with the aid of purification procedure by crystallization to effectively remove the undesired τ-isomer without resorting to silica gel column chromatography. This means that the present synthetic procedure can be used for large-scale production without any obstacles.

Development of enantioselective synthetic routes to (-)-kinamycin F and (-)-lomaiviticin aglycon.

The development of enantioselective synthetic routes to (-)-kinamycin F (9) and (-)-lomaiviticin aglycon (6) are described. The diazotetrahydrobenzo[b]fluorene (diazofluorene) functional group of the targets was prepared by fluoride-mediated coupling of a β-trimethylsilylmethyl-α,β-unsaturated ketone (38) with an oxidized naphthoquinone (19), palladium-catalyzed cyclization (39→37), and diazo transfer (37→53). The D-ring precursors 60 and 68 were prepared from m-cresol and 3-ethylphenol, respectively. Coupling of the β-trimethylsilylmethyl-α,β-unsaturated ketone 60 with the juglone derivative 61, cyclization, and diazo transfer provided the advanced diazofluorene 63, which was elaborated to (-)-kinamycin F (9) in three steps. The diazofluorene 87 was converted to the C(2)-symmetric lomaiviticin aglycon precursor 91 by enoxysilane formation and oxidative dimerization with manganese tris(hexafluoroacetylacetonate) (94, 26%). The stereochemical outcome in the coupling is attributed to the steric bias engendered by the mesityl acetal of 87 and contact ion pairing of the intermediates. The coupling product 91 was deprotected (tert-butylhydrogen peroxide, trifluoroacetic acid-dichloromethane) to form mixtures of the chain isomer of lomaiviticin aglycon 98 and the ring isomer 6. These mixtures converged on purification or standing to the ring isomer 6 (39-41% overall). The scope of the fluoride-mediated coupling process is delineated (nine products, average yield = 72%); a related enoxysilane quinonylation reaction is also described (10 products, average yield = 77%). We establish that dimeric diazofluorenes undergo hydrodediazotization 2-fold faster than related monomeric diazofluorenes. This enhanced reactivity may underlie the cytotoxic effects of (-)-lomaiviticin A (1). The simple diazofluorene 103 is a potent inhibitor of ovarian cancer stem cells (IC(50) = 500 nM).

Synthesis and reactions of new 1,2- and 1,3-cyclopentadienyl disubstituted cobalt sandwich compounds (η5-C5H3R2)Co(η4-C4Ph4) (R[dbnd]CH2OH, CHO, C[tbnd]CH, CH2N3, CH2NH2, CH2OAc, CH[dbnd]NPh)

Synthesis and characterization of a series of 1,3- and 1,2-cyclopentadienyl disubstituted derivatives of η5-CpCo(η4-C4Ph4) has been described. The 1,3- and 1,2-cyclopentadienyl diester derived cobalt sandwich compounds {η5-C5H3[C(O)OMe]2}Co(η4-C4Ph4) were prepared by literature procedure and were separated by column chromatography. The reduction of these diester derivatives using LiAlH4 gave the bis(hydroxymethyl) derivatives, [1,3-η5-C5H3(CH2OH)2] Co(η4-C4Ph4) 1 and [1,2-η5-C5H3(CH2OH)2]Co(η4-C4Ph4) 2 which were oxidized to the dialdehydes [1,3-η5-C5H3(CHO)2]Co(η4-C4Ph4) 3 and [1,2-η5-C5H3(CHO)2]Co(η4-C4Ph4) 4 by using tetrapropylammonium perruthenate along with N-methyl morpholine oxide. Reaction of the dialdehydes with (chloromethyl)triphenylphosphonium chloride/n-BuLi followed by elimination of HCl using n-BuLi resulted in the 1,2- and 1,3-cyclopentadienyl disubstituted dialkynes [1,3-η5-C5H3(CCH)2]Co(η4-C4Ph4) 5 and [1,2-η5-C5H3(CCH)2]Co(η4-C4Ph4) 6. The reactions of 1 and 2 with NaN3 in acetic acid resulted in the bis(azidomethyl) derivatives [1,3-η5-C5H3(CH2N3)2]Co(η4-C4Ph4) 7 and [1,2-η5-C5H3(CH2N3)2]Co(η4-C4Ph4) 8. Heating of bis(hydroxymethyl) compounds 1 and 2 in acetic acid at 85–90 °C resulted in the formation of bis(2-acetoxymethyl) derivatives [1,3-η5-C5H3(CH2OAc)2]Co(η4-C4Ph4) 9 and [1,2-η5-C5H3(CH2OAc)2]Co(η4-C4Ph4) 10. The reactions of 1 and 2 with thiophenol in the presence of trifluoroacetic acid in dichloromethane gave bis(phenylmethyl thioether) derivatives 11 [1,3-η5-C5H3(CH2SPh)2]Co(η4-C4Ph4) and [1,2-η5-C5H3(CH2SPh)2]Co(η4-C4Ph4) 12. The click reaction of the 1,2-dialkyne 6 with benzyl azide resulted in the 1,2-bis(triazole) derivative 13. The 1,3-diazide 8 was reduced to bis(aminomethyl) derivative [1,3-η5-C5H3(CH2NH2)2]Co(η4-C4Ph4) 14. Condensation of the 1,3-dialdehyde 3 with aniline resulted in the 1,3-bis(phenylimino) derivative 15. All the new compounds synthesized in this study were characterized by 1H and 13C NMR, FT-IR, HRMS, CHN analysis. The compounds 2–6, 8 and 10 have also been structurally characterized by single crystal X-ray diffraction analysis.

Efficacious N-protection of O-aryl sulfamates with 2,4-dimethoxybenzyl groups

Sulfamates are important functional groups in certain areas of current medicinal chemistry and drug development. Alcohols and phenols are generally converted into the corresponding primary sulfamates (ROSO(2)NH(2) and ArOSO(2)NH(2), respectively) by reaction with sulfamoyl chloride (H(2)NSO(2)Cl). The lability of the O-sulfamate group, especially to basic conditions, usually restricts this method to a later stage of a synthesis. To enable a more flexible approach to the synthesis of phenolic O-sulfamates, a protecting group strategy for sulfamates has been developed. Both sulfamate NH protons were replaced with either 4-methoxybenzyl or 2,4-dimethoxybenzyl. These N-protected sulfamates were stable to oxidising and reducing agents, as well as bases and nucleophiles, thus rendering such masked sulfamates suitable for multi-step synthesis. The protected sulfamates were synthesised by microwave heating of 1,1'-sulfonylbis(2-methyl-1H-imidazole) with a substituted phenol to give an aryl 2-methyl-1H-imidazole-1-sulfonate. This imidazole-sulfonate was N-methylated by reaction with trimethyloxonium tetrafluoroborate, which enabled subsequent displacement of 1,2-dimethylimidazole by a dibenzylamine (e.g. bis-2,4-dimethoxybenzylamine). The resulting N-diprotected, ring-substituted phenol O-sulfamates were further manipulated through reactions at the aryl substituent and finally deprotected with trifluoroacetic acid to afford a phenol O-sulfamate. The use of 2,4-dimethoxybenzyl was particularly attractive because deprotection occurred quantitatively within 2 h at room temperature with 10% trifluoroacetic acid in dichloromethane. The four key steps in the protocol described [reaction of 1,1'-sulfonylbis(2-methyl-1H-imidazole) with a phenol, methylation, displacement with a dibenzylamine and deprotection] all proceeded in very high yields.

Side Chain Anchoring of Tryptophan to Solid Supports Using a Dihydropyranyl Handle: Synthesis of Brevianamide F

The multifunctional character of tryptophan has made it a target for the development of new molecules with therapeutic applications. In this sense the design of alternative solid phase routes would allow the widening of synthetic possibilities to access these molecules through conventional or combinatorial strategies. The present work describes a new strategy for side-chain anchoring of tryptophan to dihydropyranyl-functionalized polystyrene resins and its application to the synthesis of the natural diketopiperazine Brevianamide F. For this study a new handle (4-[(3,4-dihydro-2H-pyran-2-yl)methoxy]benzoic acid) was prepared in order to functionalize aminomethyl or methylbenzhydrylamine resins. A preliminary study in solution using Fmoc-Trp-OR (R = Allyl or Me) and suitable resin models showed that the formation of an hemiaminal linkage with the indole system could be brought about by either conventional or microwave heating in 1,2-dichloroethane and in the presence of pyridine p-toluenesulfonate in yields of 70–95% practically without the formation of sub-products. On the other hand the amino acid could be liberated from the resin at room temperature in yields of up to 90% using trifluoroacetic acid in dichloromethane in the presence of 1,3-dimethoxybenzene as a cation scavenger. The conditions found in solution for the reversible formation of the hemiaminal were only reproducible in solid-phase work using conventional heating. These conditions were used in the synthesis of Brevianamide F, furnishing the diketopiperazine in an overall yield of 56%. These results demonstrate the potential of this strategy for the preparation of new molecules based upon tryptophan as a synthetic precursor.

Osteoblasts mineralization with Composite nanofibrous substrate for Bone tissue regeneration

Several studies are currently ongoing to construct synthetic bone-like materials with composites of natural and polymeric materials with HA (hydroxyapatite). The present study aims to fabricate composite nanofibrous substrate of Chit/HA (chitosan/HA - 80:25) prepared by dissolving in TFA/DCM (trifluoroacetic acid/dichloromethane) (70:30, w/w) for 5 days and electrospun to fabricate a scaffold for bone tissue engineering. HA (25 wt %) was sonicated for 30 min to obtain a homogenous dispersion of nanoparticles within the Chit (80 wt %) matrix for fabricating composite nanofibrous scaffold (Chit/HA). The nanofibres of Chit and Chit/HA were obtained with fibre diameters of 274 ± 75 and 510 ± 198 nm, respectively, and characterized by FESEM (field emission scanning electron microscopy) and FTIR (Fourier transform infrared). The interaction of hFOBs (human fetal osteoblasts) and nanofibrous substrates were analysed for cell morphology (FESEM), mineralization [ARS (Alizarin Red-S) staining], quantification of minerals and finally identified the elements present in Chit/HA/osteoblasts by EDX (energy-dispersive X-ray) analysis. EDX analysis confirmed that the spherulites contain calcium and phosphorus, the major constituents in calcium phosphate apatite, the mineral phase of the bone. Mineralization was increased significantly (P<0.001) up to 108% in Chit/HA compared with Chit nanofibres. These results confirmed that the electrospun composite Chit/HA nanofibrous substrate is a potential biocomposite material for the proliferation and mineralization of hFOBs required for enhanced bone tissue regeneration.

Y65C Missense Mutation in the WW Domain of the Golabi-Ito-Hall Syndrome Protein PQBP1 Affects Its Binding Activity and Deregulates Pre-mRNA Splicing

The PQBP1 (polyglutamine tract-binding protein 1) gene encodes a nuclear protein that regulates pre-mRNA splicing and transcription. Mutations in the PQBP1 gene were reported in several X chromosome-linked mental retardation disorders including Golabi-Ito-Hall syndrome. The missense mutation that causes this syndrome is unique among other PQBP1 mutations reported to date because it maps within a functional domain of PQBP1, known as the WW domain. The mutation substitutes tyrosine 65 with cysteine and is located within the conserved core of aromatic amino acids of the domain. We show here that the binding property of the Y65C-mutated WW domain and the full-length mutant protein toward its cognate proline-rich ligands was diminished. Furthermore, in Golabi-Ito-Hall-derived lymphoblasts we showed that the complex between PQBP1-Y65C and WBP11 (WW domain-binding protein 11) splicing factor was compromised. In these cells a substantial decrease in pre-mRNA splicing efficiency was detected. Our study points to the critical role of the WW domain in the function of the PQBP1 protein and provides an insight into the molecular mechanism that underlies the X chromosome-linked mental retardation entities classified globally as Renpenning syndrome.

De-staining and re-staining mucins in formalin fixed paraffin sections

Re-staining of formalin fixed paraffin sections sometimes is required and this requires prior de-staining. Some simple and effective protocols for de-staining are described. Mucihematoxylin and mucicarmine can be removed with acid alcohol. Zirconyl hematoxylin can be removed with periodic acid or Sinha's fixative. Alcian blue can be removed with 5% trifluoroacetic acid in dichloromethane. Colloidal iron can be bleached in 1% household bleach in alcohol. PAS can be removed with hydrogen peroxide or ammonium hydroxide. With few exceptions, de-stained sections can be re-stained with mucihematoxylin, PAS or Gabe's trichrome.

Bis(4′‐dibutylaminostyryl)benzene: Spectroscopic Behavior upon Protonation or Methylation

We have investigated the UV/Vis absorption and emission of 1,4-bis(4'-dibutylaminostyryl)benzene (1) upon protonation with trifluoroacetic acid in dichloromethane and in acetonitrile. We find that 1 does not display significantly dynamic acidity in the excited state, that is, it is not a photoacid. Three protonation states of 1 were investigated, all of which, neutral, singly protonated, and bis-protonated, are fluorescent. As an isolable model for the mono-protonated species, a methylated derivative of 1 was prepared by reaction with methyl triflate. This species displays redshifted emission but similar absorption as the non-quaternized parent, 1. The strong observed emission of all three protonated states of 1 suggests that the kinetic photoacidity of 1* is low or absent. We assume that the lifetime of the excited state is too short to allow solvent reorganization and therefore we cannot make a statement on the thermodynamic photoacidity of the protonated forms of 1.

Synthesis of Dideoxymycobactin Antigens Presented by CD1a Reveals T Cell Fine Specificity for Natural Lipopeptide Structures

Mycobacterium tuberculosis survival in cells requires mycobactin siderophores. Recently, the search for lipid antigens presented by the CD1a antigen-presenting protein led to the discovery of a mycobactin-like compound, dideoxymycobactin (DDM). Here we synthesize DDMs using solution phase and solid phase peptide synthesis chemistry. Comparison of synthetic standards to natural mycobacterial mycobactins by nuclear magnetic resonance and mass spectrometry allowed identification of an unexpected alpha-methyl serine unit in natural DDM. This finding further distinguishes these pre-siderophores as foreign compounds distinct from conventional peptides, and we provide evidence that this chemical variation influences the T cell response. One synthetic DDM recapitulated natural structures and potently stimulated T cells, making it suitable for patient studies of CD1a in infectious disease. DDM analogs differing in the stereochemistry of their butyrate or oxazoline moieties were not recognized by human T cells. Therefore, we conclude that T cells show precise specificity for both arms of the peptide, which are predicted to lie at the CD1a-T cell receptor interface.

(2,6-Dichloro-4-alkoxyphenyl)-(2,4-dichlorophenyl)methyl Trichloroacet­imidates: Protection of Alcohols and Carboxylic Acids in Solution or on Polymer Support

(2,6-Dichloro-4-methoxyphenyl)-(2,4-dichlorophenyl)-methyl trichloroacetimidate can be efficiently activated by TMSOTf (10∼100 mol%) to react with alcohols and carboxylic acids. Under these conditions a wide variety of alcohols can be transformed into the corresponding ethers in excellent yields with a slight excess of the trichloroacetimidate. The resulting ethers are not susceptible to typical deprotection conditions for benzyl and 4-methoxybenzyl ether groups, however, they can be conveniently deprotected by treatment with 30∼50% trifluoroacetic acid in dichloromethane. Polymer-bound (2,6-dichloro-4-alkoxyphenyl)-(2,4-dichlorophenyl)methyl trichloroacetimidate is useful for immobilization of alcohols and carboxylic acids.

Polymethylhydrosiloxane (PMHS)/trifluoroacetic acid (TFA): a novel system for reductive amination reactions

Polymethylhydrosiloxane (PMHS)/trifluoroacetic acid (TFA) was discovered as a novel metal-free system for reductive amination reactions. A variety of (het)aryl amines as well as a representative carbamate and urea were successfully alkylated by benzaldehyde in the presence of PMHS and TFA in dichloromethane at room temperature in moderate to excellent yields (28–87%). Furthermore, this reaction protocol was successfully applied to the alkylation of p-nitroaniline with a wide range of aldehydes, ketones, and a representative acetal to obtain the alkylated products in yields ranging from 40% to 92%. The current work represents one of the very few examples of PMHS being activated by a Brønsted acid.