Solid support synthesis of 14- and 17-membered macrocycles via the SNAr methodology

Efficient assembly of 14-membered macrocycles utilizing the S_NAr of fluorine in 3-fluoro-4-nitrobenzoic acid with the OH of 3-hydroxytyrosine on solid support is reported. The flexibility of this synthesis, as well as the excellent purity (>90%) of the final products are the distinctive characteristic of the resultant library.     

Sublattices of regular elements

Let L be an r-lattice, i.e., a modular multiplicative lattice that is compactly generated, principally generated, and has greatest element 1 compact. We consider certain subsets of L consisting of regular elements: there is a compact element with there is a principal element is a principal element with (0:X_{\alpha })=0\} . The first three subsets L_{f}, L_{sr}, and L_{r} are augmented filters on L, i.e., is a multiplicatively closed subset of $L$ with $A\in and $B\geq A$ with $B\in L$ implies $B\in and hence are sublattices of $L$ closed under multiplication. We first consider the more general situation of augmented filters on $L.$ These results are then applied to study the four previously defined subsets for $L$ an $r$-lattice or Noether lattice (i.e., an $r$-lattice with ACC). Finally, we give a brief discussion of how the results for augmented lattices can be applied to subsets of $L$ which are regular with respect to an $L$-module.     

Studies of substituted dihydroxy-p-benzoquinones as precipitate-exchange reagents

Studies of the barium salts of bromanilic acid, nitranilic acid and polyporic acid show that they are not superior to barium chloranilate as reagents for determining sulfate. Improved syntheses of polyporic acid and atromentin are presented; two new syntheses of barium bromanilate, and one new synthesis of barium nitranilate and of barium polyporate are also presented. Ultraviolet absorption spectra show that polyporic acid forms a dimer in dimethylsulfoxide solution.     

An investigation of the critical liquid-vapor properties of dilute KCl solutions

The three parameters that define the critical point, temperature, pressure, and volume have been experimentally determined by means of filling studies in a platinum-lined system for five KCl solutions ranging from 0.006 to 0.568m. The platinum-lined vessels were used to overcome the problems with corrosion experienced by earlier workers. The critical temperature (t _c), pressure (P _c), and volume (V _c) were found to fit the equations $\begin{gathered} {\text{t}}_c = 374.14{\text{ }} + {\text{ }}16.602\sqrt {\text{m}} {\text{ }} + {\text{ }}41.740{\text{m }} \pm 0.5^ \circ C \hfill \\ {\text{P}}_c = 220.9 {\text{ }} + {\text{ }}135.164{\text{m }} + {\text{ }}41.173{\text{m}}^{\text{2}} {\text{ }} \pm {\text{ }}0.5 bars \hfill \\ {\text{V}}_c = 3.155{\text{ }} - {\text{ }}1.373\sqrt m {\text{ }} + {\text{ }}0.507{\text{m }} \pm {\text{ }}0.008cm^3 - g^{ - 1} \hfill \\ \end{gathered} $ from infinite dilution to 1.0m.     

Variational derivation and extensions of distributed approximating functionals

Summary Extensions of the "Distributed Approximating Functional (DAF) approach to approximating functions and their derivatives are given. The method, although inherently approximate, can be made arbitrarily accurate, numerically stable, and computationally efficient by appropriate choice of parameters. It also provides approximate representations of quantum operators which are analytic and which can be accurate. Differences between the DAFs and more standard basis set approaches are discussed in order to clarify the properties of the DAFs. Some illustrative examples are given.Supported in part under National Science Foundation Grant CHE92-01967.The Ames Laboratory is operated for the Department of Energy by Iowa State University under Contract No 2-7405-ENG82.Supported under National Science Foundation Grants CHE-8907429 and CHE-9403416.Supported under R.A. Welch Foundation Grant E-0608.Supported under National Science Foundation Grants CHE-8907429 and CHE-9403416.     

Novel one pot synthesis of polysubstituted pyrazolo[1,5-a]- and imidazo[1,2-a]pyrimidines

We have described a convenient regioselective one-pot approach to pyrazolo[1,5-a]- and imidazo[1,2-a]pyrimidine derivatives from α,β-unsaturated imines generated in situ and amino heterocycles. Reaction is general with respect to all three components, namely (i) nitrile, (ii) aldehyde, and (iii) amino heterocycle reagents. Good yields (52-77%), convenient isolation of the targeted molecules are the distinct characteristics of the developed protocol.     

A molecule with small rotational constants containing an atom with a large nuclear quadrupole moment: The microwave spectrum of trans-1-iodoperfluoropropane

Using pulsed jet chirped-pulse, and cavity-based Fourier transform microwave spectroscopies over 900 transitions have been recorded for the title molecule in the 1–4 GHz and 8–18 GHz regions. The C₁,C₂ and C₃ carbon-13 species have been observed in natural abundance allowing a substitution structure for the CCC backbone to be determined. Nearly all the transitions observed were either a-type R branches or b-type Q branches. No c-type transitions were observed consistent with only the trans conformer being present under our experimental conditions. The χ_aa,χ_bb,χ_cc and χ_ab components of the iodine nuclear quadrupole coupling tensor have been determined. Of note, several forbidden, ΔJ±2 transitions, and one ΔJ±3 transition were observed with quite reasonable intensity. These observations have been rationalized through considerations of near degeneracies between energy levels connected via a large χ_ab value (≈1 GHz).     

On the Minimum Average Distance Spanning Tree of the Hypercube

Given an undirected and connected graph G, with a non-negative weight on each edge, the Minimum Average Distance (MAD) spanning tree problem is to find a spanning tree of G which minimizes the average distance between pairs of vertices. This network design problem is known to be NP-hard even when the edge-weights are equal. In this paper we make a step towards the proof of a conjecture stated by A.A. Dobrynin, R. Entringer and I. Gutman in 2001, and which says that the binomial tree B _n is a MAD spanning tree of the hypercube H _n . More precisely, we show that the binomial tree B _n is a local optimum with respect to the 1-move heuristic which, starting from a spanning tree T of the hypercube H _n , attempts to improve the average distance between pairs of vertices, by adding an edge e of H _n -T and removing an edge e′ from the unique cycle created by e. We also present a greedy algorithm which produces good solutions for the MAD spanning tree problem on regular graphs such as the hypercube and the torus.     

Using the complex polynomial method with Mathematica to model problems involving the Laplace and Poisson equations

The complex polynomial method variant of the well‐known complex variable boundary element method (CVBEM) is reexamined in its utility in solving Partial Differential Equations (PDE) of the Poisson and Laplace type. Because the CVBEM was recently extended to three and higher dimensions, the use of complex polynomials to solve higher dimension PDE becomes apparent and therefore the advantages afforded by the use of complex polynomials can be brought to focus on higher dimension problems. Because complex polynomials involve use of computational algorithms that require high accuracy in numerical precision, including the solution of fully populated nonsymmetric matrices, the computer program Mathematica is evaluated for use as the underlying computational engine. Furthermore, Mathematica is evaluated for its internal high‐accuracy computational features and algorithms, including ease of program setup. In this research, the new program is found to provide at least a 5‐fold increase in complex polynomial degree utilization (from degree 10 to degree 50), with computational speed less than was involved in the original degree 10 approximation of Hromadka and Guymon [ASCE J Hydraulic Eng 110 (1984), 329–339], and with exceptional computational accuracy and reporting features. The Mathematica program is quite small and is provided to the reader as freeware and can be obtained from the first author. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009