A simple and green procedure for the conjugate addition of thiols to conjugated alkenes employing polyethylene glycol (PEG) as an efficient recyclable medium

Polyethylene glycol (PEG) is found to be an inexpensive, nontoxic, environmentally friendly reaction medium for the conjugate addition of thiols to conjugated alkenes to afford the corresponding adducts in excellent yields under mild and neutral conditions. Products of undesirable side reactions resulting from polymerization are not observed. The use of PEG avoids the use of either acid or base catalysts for this conversion and moreover PEG can be recovered and reused.     

Cetyltrimethylammonium Bromide as an Efficient Catalyst for Regioselective Bromination of Alkoxy Naphthalenes with Trimethyl Benzyl Ammonium Tribromide: Synthetic and Kinetic Approach

Bromination of 2‐alkoxynaphthalene (2‐ANP) and its derivatives with trimethyl benzyl ammonium tribromide (TMBATB) did not proceed smoothly even under reflux conditions. But the addition of microconcentrations of cetyltrimethyl ammonium bromide (CTAB) to the reaction afforded dramatic rate accelerations as well as good‐to‐excellent yield of the products ranging from 70% to 90%. Reactions underwent regioselective monobromination at 1‐position of 2‐alkoxynaphthalene. The rate of bromination has been followed conductometrically. The reaction kinetics indicated first‐order kinetics in [2‐ANP] as well as in [TMBATB]. Kinetic results in the presence of CTAB were explained on the basis of the Raghavan–Srinivasan model as applied to micelle‐mediated bimolecular reactions.     

Ring-opening metathesis polymerization-derived monolithic strong anion exchangers for the separation of 5'-phosphorylated oligodeoxythymidylic acids fragments

Ring-opening metathesis polymerization (ROMP) derived monoliths were prepared from 5-norborn-2-enemethyl bromide (NBE-CH(2)Br) and tris(5-norborn-2-enemethoxy)methylsilane ((NBE-CH(2)O)(3)SiCH(3)) within the confines of surface-silanized borosilicate columns (100 mm × 3 mm I.D.), applying Grubbs' first generation benzylidene-type catalyst [RuCl(2)(PCy(3))(2)(CHPh)]. Two monoliths of the same recipe were converted into strong anion-exchangers applying two different approaches. Monolith I was prepared by a two-step reaction of the poly(NBE-CH(2)-Br) moieties with diethyl amine forming a weak-anion exchanger followed by reaction (quaternization) with ethyl iodide. Monolith II was prepared via a single-step reaction of the poly(NBE-CH(2)-Br) moieties with triethyl amine. The resulting monolithic anion-exchangers prepared demonstrated a good aptitude for the anion-exchange separation of single-stranded nucleic acids (ss-DNA). However, monolith II showed superior separation efficiency compared to monolith I indicated by sharper analyte peaks and better resolution values for the 5'-phosphorylated oligodeoxythymidylic acids fragments. On monolith II, the seven fragments of [d(pT)(12-18)] were baseline separated in less than 9 min. The influence of the buffer pH on the separation efficiency was studied applying a phosphate (0.05 mol/L, pH 7 and 8) and Tris-HCl buffer (0.05 mol/L, pH 9), respectively.     

Vanadium (III), oxovanadium (IV) and oxovanadium (V) trifluoro-methanesulfonates

V(SO₃CF₃)₃, VO(SO₃CF₃)₂ and VO(SO₃CF₃)₃ have been prepared by reacting V(O₂CCF₃)₃, VO(O₂CCF₃)₂ and VOC1₃ with HSO₃CF₃. The i.r. data suggest a bridging bidentate nature for SO₃CF₃ groups. The diffuse reflectance spectrum of V(SO₃CF₃)₃ suggests hexacoordination of vanadium, whilst that of VO(SO₃CF₃)₂ is comparable to either five or six coordinated oxovanadium (IV) systems. The magnetic moments of V(SO₃CF₃)₃ and VO(SO₃CF₃)₂ are slightly lower than the spin-only values. Thermal decomposition of these triflates is simple. All the three triflates form coordination complexes with pyridine, 2, 2′-bipyridyl and triphenylphosphine oxide.     

Chemical Synthesis and Immunological Evaluation of a Pentasaccharide Bearing Multiple Rare Sugars as a Potential Anti-pertussis Vaccine

With the infection rate of Bordetella pertussis at a 60-year high, there is an urgent need for new anti-pertussis vaccines. The lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, the B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, a pertussis-LPS-like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qβ, as a vaccine candidate. Immunization of mice with the conjugate induced robust anti-glycan IgG responses with IgG titers reaching several million enzyme-linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable and could recognize multiple clinical strains of B. pertussis, highlighting the potential of Qβ-glycan as a new anti-pertussis vaccine.     

Separation behavior of electron-beam curing derived, acrylate-based monoliths

Electron beam (EB) curing-derived monolith materials were prepared from ethyl methacrylate (EMA), trimethylolpropane triacrylate (TMPTA), 2-propanol, 1-dodecanol, and toluene within the confines of 3 mmx100 mm id glass columns, applying a total dose of 22 kGy for curing. Monolithic columns were checked for their separation behavior for selected dansylated (DNS)-amino acids as well as for cyclophilin 18. Their separation performance was compared to that of a C18-modified silica-based rigid rod (Chromoliths). In the separation of dansylated amino acids, retention times were reduced on EB-derived columns, where the peak resolution was significantly better than on a Chromolith. This finding was attributed to a larger fraction of small pores (<2.15 nm) in the EB curing-derived monoliths. Finally, EB curing-derived monoliths have been used to separate cyclophilin 18 from crude cell lysis mixtures.     

Protonated 2-methyl-1,2-epoxypropane: a challenging problem for density functional theory

Protonated epoxides feature prominently in organic chemistry as reactive intermediates. Herein, we describe 10 protonated epoxides using B3LYP, MP2, and CCSD/6-311++G calculations. Relative to CCSD, B3LYP consistently overestimates the C2-O bond length. Protonated 2-methyl-1,2-epoxypropane is the most problematic species studied, where B3LYP overestimates the C2-O bond length by 0.191 angstroms. Seventeen other density functional methods were applied to this protonated epoxide; on average, they overestimated the CCSD bond length by 0.2 angstroms. We present a range of data that suggest the difficulty for DFT methods in modeling the structure of the titled protonated epoxide lies in the extremely weak C2-O bond, which is reflected in the highly asymmetric charge distribution between the two ring carbons. Protonated epoxides featuring more symmetrical charge distribution and cyclic homologues featuring less ring strain are treated with greater accuracy by B3LYP. Finally, MP2 performed very well against CCSD, deviating in the C2-O bond length at most by 0.009 angstroms; it is, therefore, recommended when computational resources prove insufficient for coupled cluster methods.