Solid phase organic synthesis (SPOS): A novel route to diketopiperazines and diketomorpholines

Summary The solid phase synthesis of libraries containing a 1,3,4,6-tetrasubstituted-2,5-diketo-1,4-piperazine scaffold (DKP) or a 3,4,6-trisubstituted-2,5-diketo-1,4-morpholme scaffold (DKM) from -bromocarboxylic acids and amines is described. Using a design strategy which we refer to as divergent library design, both templates were prepared from a common intermediate. The general utility of this synthetic route in creating novel, non-peptidyl chemical libraries is discussed.     

A New Stereoselective Synthesis of Phosphiranes

The synthesis of phosphiranes from primary phosphines and diol ditosylates was found to be stereoselective, and chiral phosphiranes were prepared from optically pure diols. The four optical isomers of 1-mesityl-2,3-dimethylphosphirane, (2S,3S)-(+)-3, (2R,3R)-(-)-4, anti-cis-(meso)-5, and syn-cis-(meso)-6, were all synthesized from mesitylphosphine and the corresponding diol ditosylates. Compound 6 was unstable, but compounds 3, 4, and 5 were all isolated in pure form. Their structure assignments were based on the NMR coupling constants J(P-H) and J(P-C). The phosphiranes were transformed into tungsten pentacarbonyl complexes. Tungsten tetracarbonyl-triphenylphosphine complexes (22, 23, 24) of compounds 3, 4, and 5 were synthesized in high yields by the reaction of the phosphiranes and W(CO)(4)(PPh(3))(THF). The absolute stereochemistry of the phosphiranes 3, 4, and 5 was determined by X-ray crystal structure analysis of compounds 22, 23, and 24. Stereochemical effects on NMR coupling constants and mass spectra of the phosphiranes are discussed.     

Clathrate and inclusion compounds: Part V. An infrared and Raman study of the decomposition of the Hofmann aniline clathrates M(NH3)2Ni(CN)4.2C6H5NH2 {M = Cd(II) and Ni(II)}

The time-dependent changes which are observed in the infrared and Raman spectra of samples of the two Hofmann aniline clathrates M(NH₃)₂Ni(CN)₄.an₂ {M = Cd(II), Ni(II), an = C₆H₅NH₂} indicate the occurrence of a solid state ligand replacement reaction in which the aniline guest molecule replaces the coordinated ammonia to give Man₂Ni(CN)₄ as the final product. The rate of replacement is greater for the cadmium than for the nickel clathrate, and for both clathrates evacuation of the sample greatly increases the rate of replacement. The Man₂Ni(CN)₄ complexes can themselves act as host lattices forming clathrates containing guest molecules such as aniline.     

Flexible Ultrathin PolyDVB/EVB Composite Membranes for the Optimization of a Whole Blood Glucose Sensor

An ultrathin composite membrane has been developed as the outer covering barrier in a model amperometric glucose oxidase enzyme electrode. The membrane was formed by cathodic electropolymerization of divinylbenzene/ethylvinylbenzene at the surface of a gold coated polyester support membrane. Permeability coefficients were determined for O₂ and glucose across membranes with a range of polymer thicknesses. Anionic interferents (such as ascorbate), were screened from the working electrode via a charge exclusion mechanism. The enzyme electrode showed an initial 10% signal drift when first exposed to whole human blood over a period of 2 hours, after which responses remained essentially stable. Whole blood patient glucose determinations yielded a correlation coefficient of r²=0.99 compared to standard hospital analyses.     

Inclusion of multi-ring compounds byp-tert-butylcalix[5]arene

The inclusion complex ofp-tert-butylcalix[5]arene with tetralin has been characterized in the solid state by a single crystal X-ray diffraction study and by¹³C CP/MAS NMR experiments. A crystallographic mirror plane bisects the calix[5]arene and contains the tetralin molecule (which is dynamically disordered). The guest penetrates the upper rim of the calixarene and the experimental results indicate the saturated ring is imbedded most deeply.p-tert-Butylcalix[5]arene (tetralin) · 2 EtOH belongs to the monoclinic space group C2/m witha = 22.187(6),b = 15.823(6),c = 18.168(5) Å, = 99.70(2)°, andD _c = 1.09 g cm^–3 forZ = 4. Refinement based on 1652 observed reflections led to a finalR value of 0.081. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82/82129 (19 pages).     

Friedel–crafts crosslinking methods for polystyrene modification. IV. Macromolecular structure of crosslinked particles

Crosslinked polystyrene particles were prepared by Friedel–Crafts suspension crosslinking of polystyrene using 2,4-dichloromethyl-2,5-dimethyl benzene as crosslinking agent. The polymer was dissolved in nitrobenzene and reaction occurred in a 70 wt % aqueous solution of ZnCl₂ with poly(vinyl alcohol) as a suspending agent. The spherical particles produced were swollen in toluene, chloroform, and tetrahydrofuran to determine their equilbrium polystyrene volume fraction. Analysis of the crosslinked macromolecular structure gave values of number-average molecular weight between crosslinks of M?_c = 900–5900 increasing as the nominal crosslinking ratio X decreased from 0.75 to 0.0625 mol of crosslinking agent per mole of polystyrene repeating unit. Porosimetric analysis contributed to the understanding of the importance of the pore structure for swelling behavior.     

Observation and quantification of ultraviolet-induced reactive oxygen species in ex vivo human skin

Two-photon fluorescence imaging is used to detect UV-induced reactive oxygen species (ROS) in ex vivo human skin in this study. ROS (potentially H202, singlet oxygen or peroxynitrite [or all]) are detected after reaction with nonfluorescent dihydrorhodamine-123 (DHR) and the consequent formation of fluorescent rhodamine-123 (R123). The cellular regions at each epidermal stratum that generate ROS are identified. R-123 fluorescence is detected predominately in the lipid matrix of the stratum corneum. In contrast, the strongest R123 fluorescence signal is detected in the intracellular cytoplasm of the viable epidermal keratinocytes. A simple bimolecular one-step kinetic model is used for estimating the upper bound of the number of ROS that are generated in the skin and that react with DHR. After ultraviolet-B radiation (280-320 nm) (UVB) equivalent to 2 h of noonday summer North American solar exposure (1600 J m(-2) UVB), the model finds that 14.70 x 10(-3) mol of ROS that react with DHR are generated in the stratum corneum of an average adult-size face (258 cm(-2)). Approximately 10(-4) mol are potentially generated in the lower epidermal strata. The data show that two-photon fluorescence imaging can be used to detect ROS in UV-irradiated skin.     

Preparation and X-ray structure of [H3O+·18-crown-6]-[(H5O 2 + )(Cl−)2], a compound containing both H3O+ and H5O 2 + crystallized from aromatic solution

The title compound was synthesized by the reaction of [H₃O⁺·18-crown-6][Cl-H-Cl^–]·3.8 C₆H₅Me with two equivalents of H₂O. Colorless crystals, which slowly deposited from the corresponding liquid clathrate, belong to the monoclinic space group P2₁/n witha=10.648(6),b=9.571(2),c=20.801(6) Å,=98.67(5)°, andD _c=1.24 g cm^–3 forZ=4. Refinement based on 1609 observed reflections led to a finalR value of 0.072. In the crystal structure the [H₃O⁺·18-crown-6]⁺ cations are packed in layers separated by puckered sheets of [(H₅O ₂ ⁺ )(Cl^–)₂]^–.     

Target-free Stereo PIV: a novel technique with inherent error estimation and improved accuracy

A novel, accurate and simple stereo particle image velocimetry (SPIV) technique utilising three cameras is presented. The key feature of the new technique is that there is no need of a separate calibration phase. The calibration data are measured concurrently with the PIV data by a third paraxial camera. This has the benefit of improving ease of use and reducing the time taken to obtain data. This third camera also provides useful velocity information, considerably improving the accuracy of the resolved 3D vectors. The additional redundancy provided by this third perspective in the stereo reconstruction equations suggests a least-squares approach to their solution. The least-squares process further improves the utility of the technique by means of the reconstruction residual. Detailed error analysis shows that this residual is an accurate predictor of resolved vector errors. The new technique is rigorously validated using both pure translation and rotation test cases. However, while this kind of validation is standard, it is shown that such validation is substantially flawed. The case of the well-known confined vortex breakdown flow is offered as an alternative validation. This flow is readily evaluated using CFD methods, allowing a detailed comparison of the data and evaluation of PIV errors in their entirety for this technique.