High asymmetric induction in the base catalysed reaction of ethyl phenyl ketene with 1-phenylethanol and 2,2-dimethyl-1-phenylpropanol

Diastereomer ratios in $\text{4}$ as high as 99:1 are reached in the title reaction.     

THE PLASMA DISTRIBUTION OF BENZOPORPHYRIN DERIVATIVE and THE EFFECTS OF PLASMA LIPOPROTEINS ON ITS BIODISTRIBUTION

The plasma distribution and biodistribution of benzoporphyrin derivative were examined. Two analogs of benzoporphyrin derivative were mixed with human plasma in vitro and recovered in the lipoprotein fractions upon separation by chromatography or ultracentrifugation. The majority of both analogs was recovered with high density lipoprotein. The effect of prebinding benzoporphyrin derivative to lipoproteins on the biodistribution of the drug in vivo was studied in tumor bearing DBA/2J mice. At 3, 8 and 24 h post-injection, tumor and tissue samples were excised and analyzed for benzoporphyrin derivative content. Precomplexing benzoporphyrin derivative with low density lipoprotein or high density lipoprotein led to significantly (P less than 0.05) greater tumor accumulation than in aqueous solution.     

Absence of bound states in extremely asymmetric positive diatomic molecules

It is shown that the Hamiltonian for a diatomic molecule consisting ofN electrons and two dynamic nuclei with chargesZ ₁ andZ ₂ has no bound states if one of the charges is sufficiently large. The nuclear motion is completely unrestricted, and the kinetic energy of both nuclei can be included in the Hamiltonian. One of the nuclear charges can be arbitrarily small, provided that the other is sufficiently large.Research supported in part by NSF grant DMS-8908125     

Integrated Science and Mathematics Professional Development Programs

Over the past 5 years, integrated science and mathematics professional development programs for grades 4‐10 science and mathematics teachers have been designed and implemented at Wright State University. The primary goals of the programs were to enhance the science and mathematics content understanding and pedagogical knowledge of the participant teachers in order to increase teacher confidence and promote the implementation of standards‐based teaching practices in precollege classrooms. In this article, the general program structure developed and implemented over the years is discussed. Focusing on the 1999 program, evidence is presented of enhanced participant content understanding and pedagogical preparation, and specific examples of modified teacher practices are discussed.     

Total synthesis of aigialomycin D: surprising chemoselectivity dependence on alkyne structure in nickel-catalyzed cyclizations

The total synthesis of aigialomycin D was carried out using a nickel-catalyzed ynal macrocyclization as a key step. This key step allowed macrocycle assembly and formation of a disubstituted alkene and a secondary hydroxyl stereocenter in a single step, although the stereocenter was formed unselectively. An interesting side reaction involving five-membered-ring synthesis by an aldehyde/styrene cyclization was observed when macrocyclization of an alkynyl silane was attempted. A mechanistic basis for this surprising process is provided.     

Rovibrationally selected and resolved pulsed field ionization-photoelectron study of propyne: ionization energy and spin-orbit interaction in propyne cation

By using a high-resolution infrared (IR) laser to prepare propyne (C(3)H(4)) in selected rotational levels of the excited nu(1) (acetylenic C-H stretching) vibration mode prior to vacuum ultraviolet (VUV) laser pulsed field ionization-photoelectron (PFI-PE) measurements, we have obtained rotationally resolved VUV-PFI-PE spectra for the C(3)H(4) (+)(X (2)E(32,12),nu(1) (+)=1) band. The analysis of these PFI-PE spectra leads to the determination of the spin-orbit constant of A=-13.0+/-0.2 cm(-1) for the C(3)H(4) (+)(X (2)E(32,12),nu(1) (+)=1) state. Using this A constant and the relative rotationally selected and resolved state-to-state photoionization cross sections thus measured, we have obtained an excellent simulation for the VUV-PFI-PE origin band of C(3)H(4) (+)(X (2)E(32,12)), yielding a value of 83 619.0+/-1.0 cm(-1) (10.367 44+/-0.000 12 eV) for the adiabatic ionization energy of C(3)H(4) [IE(C(3)H(4))]. The present two-color IR-VUV-PFI-PE study has also made possible the determination of the C-H stretching frequencies nu(1) (+)=3217.1+/-0.2 cm(-1) for C(3)H(4) (+)(X (2)E(32,12)). The spectral assignment and simulation were guided by high-level ab initio calculations on the IE(C(3)H(4)), Franck-Condon factors for photoionization transitions, and rotational constants and vibrational frequencies for C(3)H(4) (+).     

Assignment of rovibrational transitions of propyne in the region of 2934-2952 cm(-1) measured by two-color IR-vacuum ultraviolet laser photoion-photoelectron methods

The infrared (IR) spectrum of propyne in the region of 2934-2952 cm(-1) has been recorded by the IR-vacuum ultraviolet (VUV)-photoion method. The spectrum is shown to consist of two near-resonant, but noncoupled vibrational bands: the nu2 symmetric methyl C-H stretching vibrational band and a combination vibrational band nucs. The previously unobserved Q line of the nucs band is observed. The rotational transition lines of the nu2=1 band produces IR-VUV-pulsed field ionization-photoelectron (IR-VUV-PFI-PE) signal at the C3H4+ (nu2+=1) photoionization threshold. The rotational transition lines associated with the nucs band do not produce IR-VUV-PFI-PE signal. Rotational transition lines of both vibrational bands are assigned and simulated; and ab initio calculations further confirm the assignment.     

Synthesis of chromium(III) bis(benzamidinate) complexes via single electron oxidation

Single-electron oxidation of the known Cr(II) bis(amidinate) Cr[(Me₃SiN)₂CPh]₂ (1) provides synthetic access to neutral Cr(III) complexes. The complexes Cr[(Me₃SiN)₂CPh]₂X were prepared by reaction of 1 with AgO₂CPh (X = O₂CPh, 2), of 1 with iodine in THF (X = I/THF, 3), or of 1 with iodine in pentane, followed by addition of 2-adamantanone (X = I/2-adamantanone, 4). Treatment of 2 or 3 with C₃H₅MgCl resulted in the thermally stable allyl complex (X = η³-C₃H₅, 5). A preliminary kinetics study of the reaction of 1 with excess allyl benzoate and allyl acetate was performed. The molecular structures of 2, 3 and 5 were confirmed by single crystal X-ray diffraction.     

A General Synthetic Approach for Designing Epitope Targeted Macrocyclic Peptide Ligands

We describe a general synthetic strategy for developing high‐affinity peptide binders against specific epitopes of challenging protein biomarkers. The epitope of interest is synthesized as a polypeptide, with a detection biotin tag and a strategically placed azide (or alkyne) presenting amino acid. This synthetic epitope (SynEp) is incubated with a library of complementary alkyne or azide presenting peptides. Library elements that bind the SynEp in the correct orientation undergo the Huisgen cycloaddition, and are covalently linked to the SynEp. Hit peptides are tested against the full‐length protein to identify the best binder. We describe development of epitope‐targeted linear or macrocycle peptide ligands against 12 different diagnostic or therapeutic analytes. The general epitope targeting capability for these low molecular weight synthetic ligands enables a range of therapeutic and diagnostic applications, similar to those of monoclonal antibodies.