THE QUALITATIVE CONTENT OF RENEWABLE RESOURCE MODELS

This paper analyzes the extent to which standard dynamic renewable resource models possess refutable implications. Both the steady state comparative static and local comparative dynamic properties of the standard model are studied. A unified framework is developed which enables one to analyze the qualitative properties of any standard renewable resource model. This is achieved by explicitly linking the local stability, steady state comparative static, and local comparative dynamic properties of the model.     

Synthesis of marrubiin

The synthesis of marrubiin has been achieved starting from the keto lactone (II) which was prepared stereoselectively from the known keto ester (XI).     

Nonlinear response of the benzene molecule to strong magnetic fields

The fourth-rank hypermagnetizability tensor of the benzene molecule has been evaluated at the coupled Hartree-Fock level of accuracy within the conventional common-origin approach, adopting gaugeless basis sets of increasing size and flexibility. The degree of convergence of theoretical tensor components has been estimated allowing for two different coordinate systems. It is shown that a strong magnetic field perpendicular to the plane of the molecule causes a distortion of the electron charge density, which tends to concentrate in the region of the C-C bonds. This charge contraction has a dynamical origin, and can be interpreted as a feedback effect in terms of the classical Lorentz force acting on the electron current density.     

Theoretical study of magnetic properties of ammonia molecule in nonuniform magnetic field

The interaction Hamiltonian within the Bloch gauge for the potentials of the electromagnetic field has been used to define magnetic multipole moment operators and operators for the magnetic field of electrons acting on the nuclei of a molecule in the presence of nonhomogeneous external magnetic field. Perturbation theory has been applied to evaluate the induced electronic moments and magnetic field at the nuclei. Multipole magnetic susceptibility and nuclear magnetic shielding tensors have been introduced to describe the contributions arising in nonuniform fields, and their origin dependence has been analyzed. Extended numerical tests on the ammonia molecule in a static, nonuniform magnetic field have been carried out, using the random-phase approximation within the framework of accurate Hartree-Fock zero-order wavefunctions, and allowing for both angular momentum and torque formalisms in the calculation of paramagnetic contributions.     

Novel selenium-containing non-natural diamino acids

The general synthesis of a new class of non-natural diamino acids, 2-amino-3-[(2′-aminoalkyl)seleno]propanoic acids, or Se-(aminoalkyl)selenocysteines, is reported. Under the conditions devised, enantiopure N-Boc-protected β-l-iodoamines, which are readily generated from proteinogenic α-amino acids, were treated with the selenolate anion obtained from NaBH₄ splitting of the Se-Se bond in commercial l-selenocystine. The Se-alkylation products were enantiomerically pure and the reaction is high yielding (92-98%), without any detectable traces of accompanying by-products.     

Conjugated Azoalkenesi Part III. Synthesis of Sone Phosphorous Azoalkenes

Recently, some of us reviewed the synthes is and chemical reactions of conjugated azoalkenes.¹ Emphasis was placed on the fact that these derivatives represent at the same time interesting products and useful intermediates in organic chemistry. In fact, conjugated azoolefins undergo a wide range of 1,4-additions, (3+2)- and (4+2)-cycloadditions allowing various functionalizations of the carbon atom adjacent to the carbonyl group, and the construction of many types of interesting five - and six-membered heterocycles, such as widely substituted pyrrole and pyridazine rings. These relevant synthetic objectives appear not to be smoothly obtained by other procedures. In addition, many of the compounds produced from conjugated azoalkenes can profitably be employed in the preparation of natural, pharmaceutical, and phytopharmaceutical products.¹     

Chemistry of Ethanediyl S,S-Acetals 9-Asymmetric Synthesis of Chiral cis Allylic Alcohols

(2Z,1S)-1,3-diphenyl-2-propenol (3) is obtained from the chiral 5,6-dihydro-1,4-dithiin 1b in two steps and 60% enantiomeric excess. Combining our previously reported stereoselective double bond formation and this 1,4 asymmetric induction introduces a new route to chiral allylic alcohols with cis geometry from simple aldehydes and methyl ketones.     

Effect of metal ions in organic synthesis. Part XIII. Selective regeneration of hydroxyl and carboxyl groups from some derivatives by copper (II) ion-promoted hydrolysis

Acetyl derivatives of alcoholic and phenolic hydroxyl groups represent not only useful educts, intermediates and products in organic, bioorganic and pharmaceutical chemistry, but also interesting derivatives for isolation, purification and characterization of alcohols and phenols (especially for natural products). Furthermore, the acetylation reaction is frequently used for the protection of hydroxyl function. In general, however, acetoxy-groups may be highly resistent to hydrolysis so that their conversion into hydroxyl groups often requires strongly basic or acidic media, expensive and/or hardly available reagents, complicated procedures. These conditions may be incompatible with sensitive substrates or with other insufficiently stable groups present in the molecular residue.^1,2 Very similar arguments are sound for some hydrazide derivatives of carboxylic acids.^1,3,4     

Effect of Metal Ions in Organic Synthesis. part XVI. Knoevenagel Condensations of Aldehydes and Tosylhydrazones with 2,4-Pentanedione by Copper (II) Chloride-Catalyzed Reaction

Based on some of our previous findings on the activity of some metal ions in certain organic reactivities,¹ we have now studied the Knoevenagel condensations of aliphatic and aromatic aldehydes or their tosylhydrazone derivatives with 2,4-pentanedione. In the presence of catalytic amounts of anhydrous copper (II) chloride, these compounds react in tetrahydrofuran at room temperature, affording the corresponding alkylidene or arylidene compounds in 48–98% yields.