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In this study, antimicrobial polymers are synthesized by the organocatalytic ring-opening polymerization of an eight-membered heterocyclic carbonate monomer that is subsequently quaternized with methyl iodide. These polymers demonstrate activity against clinically relevant Gram-positive Staphylococcus epidermidis and Staphylococcus aureus, Gram-negative Escherichia coli and Pseudomonas aeruginosa, and fungus Candida albicans with fast killing kinetics. Importantly, the polymer efficiently inhibits biofilm growth and lyses existing biofilm, leading to a reduction in biomass and cell viability. In addition, the macromolecular antimicrobial is less likely to induce resistance as it acts via a membrane-lytic mechanism. The polymer is not cytotoxic toward mammalian cells with LD50 of 99.0 ± 11.6 mg kg-1 in mice through i.v. injection. In an S. aureus blood stream infection mouse model, the polymer removes bacteria from the blood more rapidly than the antibiotic Augmentin. At the effective dose, the polymer treatment does not damage liver and kidney tissues or functions. In addition, blood electrolyte balance remains unchanged after the treatment. The low cost of starting materials, ease of synthesis, nontoxicity, broad spectrum activity with fast killing kinetics, and in vivo antimicrobial activity make these macromolecular antimicrobials ideal candidates for prevention of sepsis and treatment of infections.

patients with normal or only mildly impaired kidney function but one that requires closemonitoring due to the possibility of worsening kidney function, particularly in patients with chronic kidney disease. Our retrospective observational review suggests that further study of this treatment is warranted. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology (Shewan and Coats 2010;144:1–2).

Parallel Fragmentation Monitoring (PFM), which is an analogue of selected reaction monitoring (SRM), is a recently developed method for quantification of small molecules by MALDI-TOF/TOF mass spectrometry (MS). It is well known that isobaric interference substances can be occasionally present in complex biological samples, and affect the accuracy of measurement by SRM. Unfortunately, by design it is not possible to assess whether isobaric interference happens in a SRM analysis. In contrast, the unique design of PFM should allow quick inspection for isobaric interference and subsequent correction. In this study, using arginine as an example, interference effect of isobaric structural analogs on the quantification of citrulline by PFM was evaluated. Our results showed that the presence of arginine affected the measured concentrations of citrulline standard solutions in a concentration dependent manner. Such interference could be observed readily in the MS/MS spectra, and contributed by [arginine+H-NH3](+) fragment ion. Because of having highly similar mass, (13)C-isotope of [arginine+H-NH3](+) fragment ion overlapped with monoisotope of [citrulline+H-NH3](+) fragment ion, which was used as the report ion for quantification. However, such interference could be mathematically eliminated or minimized through estimation of the signal intensity of the (13)C-isotopic peak of [arginine+H-NH3](+) from the intensity of the corresponding monoisotopic peak according to isotope distribution of elements. Furthermore, the presence of interfering fragment ions could be avoided by optimizing MALDI ionization condition. In conclusion, isobaric interference can happen in PFM, but can be easily identified in the mass spectra and eliminated (minimized) with simple methods.

A critical evaluation of model-fitted and observed 1H NMR spin-lattice relaxation time data (T1) of methylaluminoxane (MAO) dissolved in toluene suggests that the relaxation time of MAO is predominantly controlled by rotational motions. Within the Al concentration (CAl) range (10–3M T > 20°C) studied, the diffusion of MAO contributes with less than 20% (at the maximum concentration investigated) to the overall relaxation rate. For concentrations smaller than 0.5 M, the diffusion has no significant impact on the spin-lattice relaxation time (

The shape of the solid-state proton NMR Free Induction Decay (FID) of a molten polyethylene (PE) sample has been examined as a function of time during isothermal crystallization in situ. The crystallization rate as a function of crystallization temperature is derived and the results discussed within a thermodynamic framework. A slight increase in molecular correlation times (in the microsecond range) with crystallization time was revealed for both the crystalline and intermediate phases. In particular, the molecular mobility within the intermediate phase is found to be approximately four times faster than in the crystalline phase. During isothermal crystallization the more mobile molecular phase is claimed to be composed of two “sub-phases”, an amorphous phase and a molten phase. The latter “sub-phase”, which represents 100% of the polymer at the start of the crystallization (completely molten sample), transforms completely to crystalline, amorphous and intermediate phases during the crystallization process. The actual temperature region of super-cooling, which can be probed by the present NMR technique, covers approximately 10 K and is discussed in the text.

The effect of pore surface hydrophilic/hydrophobic character on n-hexane diffusion within MCM-41 particles was investigated by PFG NMR at different pore fillings. Starting with totally filled pores, the n-hexane diffusivity within MCM-41 particles is significantly enhanced as the pore filling is decreased until it reaches a maximum value. The diffusivity is shown to decline again at a very low pore filling. This is rationalized in terms of a a three-component parallel diffusion mechanism, in which a surface diffusion, an interface diffusion and a liquid phase diffusion are involved. The influence of surface property variations on the molecular diffusivity in MCM-41 is enhanced in partially filled samples.

A water saturated cement paste (w=ca 0:7) confined in a solution of methanol saturated with a fluorescent dye showed complete exchange of water after 10 days. However, after exchange the concentration of dye within the cement paste was less than 50% compared to the expected equilibrium value. This result is rationalized by the much larger solubility of dye in methanol compared to water, by more than two orders of magnitude. The diffusion of dye into the cement paste is thus a rather complex process, likely to involve precipitation at the water/methanol interphase, followed by an increasing solubility as more methanol enters the cement paste. The 1 H nuclear magnetic resonance spectral analysis suggests that methanol and/or dye reacts with the cement paste. D 2000 Elsevier Science Ltd. All rights reserved.

The pore dimension of a reference MCM-41 material was reduced in a controlled manner by successive silylation with tetrachlorosilane. Also, the surface of these materials was modified by temperature treatment, resulting in a reduction of the concentration of surface silanol groups. Pulsed field gradient (PFG) NMR diffusion measurements of n -hexane confined in these modified MCM-41 samples have been performed and the results discussed within the Gaussian phase distribution and short gradient pulse approximations. The observed increase of the mean residence time with increasing diffusion time of the confined n -hexane suggests a distribution of channel lengths to exist.

The crosslinking of poly(vinyl alcohol) (PVA) with glutaraldehyde at 80 °C was characterized by viscosity and pulse field gradient (PFG) nuclear magnetic resonance (NMR) techniques. NMR signified an initial dormant period of approximately 6 hr, in which the self-diffusion coefficient of PVA was found to be constant and independent of time. During the next 7 hr (the “primary” gel period), this induction period was succeeded by a fast decay of the self-diffusion coefficient of rate (9.13 ± 0.45) × 10−5 sec−1 followed by a slower decay rate of (3.22 ± 0.30) × 10−5 sec−1 (the “secondary” gel period). The viscosity of the solution showed the same time behavior, i.e. an initial dormant period (∼ 6 hrs), followed by a fast increase of the viscosity for the next 7 –8 hr. During the “secondary” gel regime, the viscosity became too large to be reliably determined. However, within the time regime where both techniques produced reliable data, they gave identical information regarding the kinetics of the gel process, suggesting that PFG NMR enables in situ monitoring of gelation within porous materials (for instance sandstone). Copyright © 2000 John Wiley & Sons, Ltd.

Solid-state proton NMR free induction decay (FID) during isothermal (394 K) crystallization from a molten polyethylene sample has been investigated. On the basis of deconvolution of the FID signal, three different phases are assigned and their relative distribution during crystallization determined. The results are discussed in light of the Avrami model. The formation of the crystalline phase during the primary crystallization time regime increases approximately with the square root of crystallization time. Kinetic data regarding the crystallization process are obtained and discussed.

Multinuclear (27A1, 19F, 13C, and 1H) NMR measurements at room temperature of aqueous solutions containing 2 M Al(NO3)3, 2.1 M morpholine, in the presence and absence of 1 M HF, suggest that morpholine is a chemically inactive specie. The proton and carbon chemical shifts of morpholine in the two solutions reveal the same pH dependence, suggesting that morpholine can be used as a probe molecule for pH determination. Moreover, the broad peaks observed in the 19F and 27A1 NMR spectra are consistent with the formation of multinuclear Al species and Al−F complexes. The observed changes in peak intensities of these same nuclei as a function of pH are in semiquantitative agreement with corresponding intensities calculated from chemical equilibrium reaction models. A more detailed spectral analysis reveals some discrepancies between observed and calculated intensities and is discussed in the text.

The gelation of polyvinylalcohol with glutaraldehyde confined in a water/ oil (= 3/1 in volume ratio) saturated sandstone (Bentheimer) was characterized by H NMR spin-lattice relaxation rate (1/ T)measurements and Pulse Field Gradient (PFG) NMR diffusion measurements. The gelation rate was found to be (12.8 ± 1.3) 10−1 5−1 at 340 K, which is approximately an order of magnitude faster than in bulk solution. In comparison, the gelation rate within the same porous material containing no oil phase was even faster, by a factor of 2.

The gelation of a polyvinylalcohol–glutaraldehyde–water solution confined in a Bentheimer sandstone was characterized by carrying out 1H-n.m.r. spin-lattice relaxation rate measurement (1/T1) and pulse field gradient diffusion (D) measurements at 67°C. At any time during the gel reaction neither the longitudinal magnetization versus storage time nor the echo-amplitude versus gradient strength (squared) could be described by single exponential functions. In order to characterize these multi-exponential decay curves by a minimum number of parameters a gaussian type of distribution function (Rayleigh distribution) in 1/T1 and D were adopted. When implementing these distribution functions and fitting all spin-lattice relaxation data and diffusion data simultaneously, in order to constrain the fitting more effectively, the two n.m.r. derived parameters (1/T1 and D) were found to give consistent results. During gelation the average relaxation rate and the average diffusion coefficient versus reaction time were found to be described by a first order rate process with a rate constant equal to 18×10−5 s−1. Also, the widths of the two distribution functions were found to decrease with reaction time. Moreover, the gelation rate within the Bentheimer sandstone was found to be significantly faster compared to the gelation rate of the bulk solution.

Diffusion of ethanol into water-saturated white cement pastes has been investigated by carbon and proton nuclear magnetic resonance (NMR). The diffusion of ethanol was shown to be Fickian, assuming one-dimensional diffusion under perfect sink boundary conditions. Derived diffusion coefficients were found to increase with increasing water/cement (w/c) ratio from (2.7 ± 0.5) 10 −8 cm 2 /s at w/c = 0.30 to (59 ± 5) 10 −8 cm 2 /s at w/c = 1.0. At the end of the exchange process, only a fraction of the total volume of water is exchanged with ethanol, varying from 60% for samples containing mainly micro- and mesopores to about 80% for samples where additional capillary pores are present. Time needed to reach 90% and 95% exchange of the total intrudable amount of ethanol in cylindrical samples with diameter of 5.5 mm varied from 1 day to nearly 3 weeks. This has importance for exchange in larger samples with typical diameters of 10 mm or more (as used in mercury intrusion porosimetry), which may require on the order of months for 90% exchange to take place. The mole fraction of ethanol and water in the pore system was determined from sampled carbon and proton NMR spectra vs. exchange time by comparing H 2 O-saturated and D 2 O-saturated samples. At the end of the exchange process, water was found to occupy the remaining volume not accessible to ethanol. In the tested w/c ratio range, the water content in all samples is below the value where damage to the pore structure normally occurs due to internal tension when exposed to drying. An empirical relationship between chemical shift of the CH 3 CH 2 OH/H 2 O peak and mole fraction of ethanol is derived, enabling the mole fraction of ethanol from the NMR peak to be estimated.

Mesoporous MCM-41 materials are ideal model systems for fundamental adsorption studies owing to their regular and well-defined pore geometry. The effect of pore dimension and pore surface hydrophobicity on the diffusion of n-hexane confined in MCM-41 was investigated by modifying the pore surface chemistry and the pore dimension of a mesoporous MCM-41 reference material with a pore diameter of 37.5 A and a crystal dimension of approximately 6 μm. The modification of the MCM-41 reference material was carried out in a controlled manner by silanation as discussed in the text. PFG-NMR measurements at room temperature revealed a 40% reduction in the diffusion coefficient when changing only the hydrophobicity (by reaction of the pore surface with SiCH3Cl3) of the pore surface. Moreover, an increase in the mobility of n-hexane of more than 80% was observed when decreasing the pore dimension from 37.5 A to approximately 33.5 A (by reaction of the pore surface with SiCl4). The surface-to-volume (S/V)-ratio of the materials (as derived by NMR diffusion measurements) was found to be three orders of magnitude less than the S/V-ratio determined by N2-adsorption and will be discussed in the text.

Proton n.m.r. relaxation times ( T 1 , T 2 ), chemical shift and line width of the solvent water protons in a polyvinylalcohol (PVA)-glutaraldehyde-water solution confined in a porous material (glass beads) revealed no significant changes during crosslinking and gel formation. Also, the self-diffusion coefficient was constant and identical to the self-diffusion coefficient of bulk water (2 × 10 −5 cm 2 s −1 ) during the reaction. Due to the smaller self-diffusion coefficient of the polymer molecules the solvent water resonance peak could be completely removed from the spectrum by applying a pulse gradient spin-echo technique, leaving only the signal from the polymer amenable for detection. In spite of the broadening effect caused by susceptibility differences between the solid porous matrix and the confined fluid, the PVA peaks were easily resolved. The observed distribution of self-diffusion coefficients of PVA could be approximated by three single diffusion coefficients ranging from 10 −6 to 10 −9 cm 2 s −1 at 25°C. The slower diffusion coefficient was found to decrease by almost an order of magnitude during the reaction with a rate of change of approximately 3 × 10 −5 s −1 at 80°C.

Model improvements related to the analysis of 1H NMR signal intensity vs temperature (IT-curve) of a fluid confined in porous materials are presented enabling pore size distribution, specific surfa...

Porous materials are characterized by a finite and discrete number of pore radii by deconvoluting the respective mercury intrusion porosimetry (MIP) curves. Introducing a perturbed cylindrical pore model enables these MIP radii to be correlated to the NMR spin−lattice relaxation time T1 of the pore-confined water to give the surface-to-volume ratio (S/V) of the pores. The technique is exemplified using four different well-hydrated white Portland cement pastes covering a wide distribution of pore sizes. However, the technique should be of general use when characterizing high surface-to-volume ratio materials.

1H-NMR spin lattice relaxation times, T1, of water occupying the pore system in white hydrated cement pastes have been measured to probe the effect of drying and freeze/thaw cycling on the pore structure. Surface to volume ratios and specific surface areas are derived from these NMR measurements. Specific surface areas vary from 132 m2/g for wc = 0.30 to 242 m2/g for wc = 0.70. A significant increase in T1 is observed after drying tests performed at 105 °C on pastes with wc-ratios 0.30, 0.40, 0.60 and 0.70 corresponding to a reduction in specific surface area of 33.0, 25.0, 7.1 and 6.5%, respectively. Line width measurements showed significant reduction only for the wc = 0.30 sample. The results are in agreement with earlier work and imply that the pore structures related to micro and meso pores are more vulnerable to drying than the coarser pore structures. Freeze/thaw cycling show no significant changes in T1 after 25 cycles although all samples except one are fragmented by frost action. However, a small increase is observed after 175 cycles for samples with the lower wc-ratios.

A comprehensive n.m.r. characterization of a low-density polyethylene (LDPE) sample with respect to the distribution of short branches, saturated and unsaturated long branch/chain ends is presented. High precision carbon chemical shift values of all assigned resonance peaks with standard deviations of less than 0.005 ppm (at 403K and 75 MHz carbon resonance frequency) were obtained by mathematical deconvolution of the carbon spectrum, thus enabling a differentiation not only of short branches (Cn

Assuming the heat of fusion (Δhf) of a material confined in a porous material to be approximated by a function Δhf = Δh0 (1 + a0(103/T) + a1(103/T)2), where T is the absolute temperature, a theoretical model is derived that enables the coefficients ai to be determined from a combined use of NMR and calorimetric measurements. The model has been applied on solid ice confined in cement pastes resulting in a0 = −0.136 K and a1 = −0.00413 K2 in the temperature range 273 K > T > 210 K. Δh0 was determined from the known value of Δhf of bulk water at 273 K, giving Δh0 = 749 J/g. Likewise, assuming the surface tension (γ) of the ice−water interface to be approximated by a corresponding second-order polynomial in 1/T, i.e., γ = γ0 (1 + b0(103/T) + b1(103/T)2), the coefficients bi were determined from the Gibbs−Thomson equation: ΔT = Kf(γ/ρΔhf)(1/R), where Kf is a constant, ρ the density, and ΔT the lowering of the melting point of ice confined in pores with radius R. The model fit revealed a best fit to a linear f...

Natural products continue to provide ever-increasing challenges to synthetic chemists with their complex and sensitive structures. With proper selection, these challenges can be turned into wonderful opportunities to invent and discover new synthetic reactions, to design new strategies and to fashion novel molecular architectures. Developments in these areas often profoundly influence and shape the science of chemical synthesis, biology and medicine. In this article, a number of recent total syntheses of challenging natural substances from the authors's laboratories are highlighted.

Proton n.m.r. has been used to study the reaction between poly(vinyl alcohol) (PVA) and two different dialdehyde crosslinkers during gel formation (gels for improved oil recovery applications). The rate of formation of covalent bonds between PVA and glutaraldehyde in acidic saline water solutions was found to be of first order with respect to both the H 1 concentration and the formal dialdehyde concentration. The activation energy was found to increase with increasing dialdehyde concentration and increasing pH (3.2–4.7). The corresponding reaction rate of formation of covalent bonds between PVA and butenedial in the PVA/2,5-dimethoxy-2,5-dihydrofuran system at the same pH and temperature was found to be an order of magnitude less. Also, the activation energy was higher by approximately 50% as compared with the PVA/glutaraldehyde system. Possible reaction pathways for the generation of PVA-dialdehyde gels are discussed.

The concept of matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) was first reported in 1985. Since then, MALDI MS technologies have been evolving, and successfully used in genome, proteome, metabolome, and clinical diagnostic research. These technologies are high-throughput and sensitive. Emerging evidence has shown that they are not only useful in qualitative and quantitative analyses of proteins, but also of other types of biomolecules, such as DNA, glycans, and metabolites. Recently, parallel fragmentation monitoring (PFM), which is a method comparable to selected reaction monitoring, has been reported. This highlights the potentials of MALDI-TOF/TOF tandem MS in quantification of metabolites. Here we critically review the applications of the major MALDI MS technologies, including MALDI-TOF MS, MALDI-TOF/TOF MS, SALDI-TOF MS, MALDI-QqQ MS, and SELDI-TOF MS, to the discovery and quantification of disease biomarkers in biological specimens, especially those in plasma/serum specimens. Using SELDI-TOF MS as an example, the presence of systemic bias in biomarker discovery studies employing MALDI-TOF MS and its possible solutions are also discussed in this chapter. The concepts of MALDI, SALDI, SELDI, and PFM are complementary to each other. Theoretically, all these technologies can be combined, leading to the next generation of the MALDI MS technologies. Real applications of MALDI MS technologies in clinical diagnostics should be forthcoming.

OBJECTIVES To evaluate the use of gut barrier proteins, liver-fatty acid binding protein (L-FABP), intestinal-fatty acid binding protein (I-FABP), and trefoil factor 3 (TFF3), as biomarkers for differentiating necrotizing enterocolitis (NEC) from septicemic/control infants and to identify the most severely affected surgical NEC from nonsurgical NEC infants. BACKGROUND Clinical features and routine radiologic investigations have low diagnostic utilities in identifying surgical NEC patients. METHODS The diagnostic utilities of individual biomarkers and the combination of biomarkers, the LIT score, were assessed among the NEC (n = 20), septicemia (n = 40), and control groups (n = 40) in a case-control study for the identification of proven NEC and surgical NEC infants. RESULTS Plasma concentrations of all gut barrier biomarkers and the LIT score were significantly higher in the NEC than in the septicemia or control group (P < 0.01). Using median values of biomarkers and the LIT score in the NEC group as cutoff values for identifying NEC from septicemic/control cases, all had specificities of 95% or more and sensitivities of 50%. Significantly higher levels of biomarkers and the LIT score were found in infants with surgical NEC than in nonsurgical NEC cases (P ≤ 0.02). The median LIT score of 4.5 identified surgical NEC cases with sensitivity and specificity of 83% and 100%%, respectively. A high LIT score of 6 identified nonsurvivors of NEC with sensitivity and specificity of 78% and 91%, respectively. CONCLUSIONS The LIT score can effectively differentiate surgical NEC from nonsurgical NEC infants and nonsurvivors of NEC from survivors at the onset of clinical presentation. Frontline neonatologists and surgeons may, therefore, target NEC infants who are most in need of close monitoring and those who may benefit from early surgical intervention.

The concept of matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) was first reported in 1985. Since then, MALDI MS technologies have been evolving, and successfully used in genome, proteome, metabolome, and clinical diagnostic research. These technologies are high-throughput and sensitive. Emerging evidence has shown that they are not only useful in qualitative and quantitative analyses of proteins, but also of other types of biomolecules, such as DNA, glycans, and metabolites. Recently, parallel fragmentation monitoring (PFM), which is a method comparable to selected reaction monitoring, has been reported. This highlights the potentials of MALDI-TOF/TOF tandem MS in quantification of metabolites. Here we critically review the applications of the major MALDI MS technologies, including MALDI-TOF MS, MALDI-TOF/TOF MS, SALDI-TOF MS, MALDI-QqQ MS, and SELDI-TOF MS, to the discovery and quantification of disease biomarkers in biological specimens, especially those in plasma/serum specimens. Using SELDI-TOF MS as an example, the presence of systemic bias in biomarker discovery studies employing MALDI-TOF MS and its possible solutions are also discussed in this chapter. The concepts of MALDI, SALDI, SELDI, and PFM are complementary to each other. Theoretically, all these technologies can be combined, leading to the next generation of the MALDI MS technologies. Real applications of MALDI MS technologies in clinical diagnostics should be forthcoming.

The pore size distribution of four commercial silica materials saturated with water have been derived from experimental 1H NMR intensity vs temperature curves (IT-curves) of the confined water. The observed melting points or transition temperatures of benzene and cyclohexane confined in the same materials are shown to be consistent with corresponding data obtained from the water IT-curves. In general, the freezing point depression (ΔT) of these fluids can be related to the pore radius R in accordance with a modified Gibbs−Thompson equation: ΔT = K/(R + d), where K and d are constants characteristic of the confined fluid. The melting point depressions of benzene and cyclohexane are shown to be more sensitive to pore radius than that of water; i.e., the two former have a larger K-value. Moreover, the average pore radius of these materials can be estimated from 1H NMR chemical shift measurements of the benzene-saturated samples. Simulation of 1H NMR spectra of benzene confined in mixtures of silica (mesopor...

A quantitative 13 C nuclear magnetic resonance analysis of an ethylene—propylene copolymer produced on a modern high-field instrument produces a spectrum with eight discrete groups of peaks. Assignment of these peaks provides eight simultaneous equations to describe the six triad distribution numbers. We have demonstrated the advantages of solving directly this over-determined set of equations. We have observed that the relative uncertainty in the different triad numbers is approximately constant, and have used this observation to discuss the uncertainties in individual triad numbers as a function of their concentration.

1H Nuclear magnetic resonance (NMR) spin-echo measurements at 268 K have been performed on water-saturated mesoporous MCM-41 materials. The pores have cylindrical geometry with diameters in the range 18–40 A and length of approximately 1 mm. Using appropriate model calculations the self-diffusion coefficient (D) of water within the pore was estimated from the Carr-Purcell-Meiboom-Gill (CPMG) spin-echo envelope curves. D was found to be in the range 0.17·10−6 to 2.3·10−6 cm2/s and could be expressed by an equation of the form D−1∝D∞−1+α·lc−2 where D∞ is the self-diffusion coefficient of bulk water (lc = ∞) and α = (2.68 ± 0.14)·10−5s. The low values for the diffusion coefficients—compared to the diffusion coefficient of bulk water — are related to the strong interaction of the water molecules with the pore surface. Moreover, the spin-spin relaxation rate ( 1 T 2 ) was related to lc by application of the Bloembergen-Purcell-Pound (BPP) model.

A novel synthetic approach to the construction of the zaragozic acids, which was used for the asymmetric synthesis of zaragozic acid A/squalestatin S1 (1), is described. Fragment 5, representing the tricarboxylic acid core portion, is assembled in three key steps: 1) Stille coupling to establish the carbon framework; 2) enantioselective dihydroxylation to introduce the absolute stereochemistry; and 3) diastereoselective dihydroxylation to complete the required carbon-oxygen connectivity. The convergency of this synthesis is demonstrated by the dithiane addition of a variety of C 1 side chains (e.g., 78) to advanced intermediate 5. A multi-event acid-catalyzed rearrangement yielded the zaragozic acid core 86, which was converted to an intermediate obtained from degradation of zaragozic acid A. A second-generation synthesis of the core of the zaragozic acids is also described. When aldehyde 90 was used instead of 5, both the yield and diastereoselectivity of the dithiane addition reaction were improved, although the degree of convergency was slightly lower.

A solid state electrochemical reactor is described in which reactants can be oxidised at high temperatures over an anode/catalyst using co-fed oxygen gas as well as electrochemically supplied oxygen. The setup permits injection of isotopic pulses in the reactant streams. The composition and isotopic distribution in the products are recorded with a quadrupole mass spectrometer. The use of the system is exemplified by oxidation of methane over a Au + SrFeO3−δ//YSZ anode at 800–850°C. Pulses of 18O2 in the stream of co-fed O2 were used to study the reactivity and products of gaseous oxygen as distinguished from the electrochemically supplied oxygen. The results indicate that the anode used supports oxygen pumping, but is only moderately active for methane oxidation. The products are mainly CO and CO2. The content of 18O in the products is low, indicating that methane oxidation takes place by 16O-rich lattice oxygen. In comparison, a reference Au//YSZ electrode was found to be a slower anode for oxygen pumping, but a better catalyst for the reaction between CH4 and gaseous O2, seemingly involving adsorbed oxygen.

Combining spin-lattice relaxation time measurements and signal intensity measurements vs temperature of water confined in mesoporous molecular sieves (MCM-4 1 materials) gives information regarding the activation enthalpy of bound water and the width of the log-normal distribution of correlation times of the water molecules. Three different water “phases” are observed which have significantly different relaxation strength. The overall spin-lattice relaxation rate is shown to be strongly dependent on the number of silanol protons. “Analytical” formulas for the average spin-lattice relaxation rates are derived.