The Computer-Aided Design,Synthesis, and Activity Prediction of New Leucine Aminopeptidase Inhibitors

The design, stereo-, and enantioselective synthesis and activity prediction of aminophosphonic acids as new leucine aminopeptidase inhibitors will be discussed.     

Photoisomerization of AZO Aromatic Chromophobes in Polyvinyl Chloride

Abstract

The synthesis and characterization of new vinyl chloride-p-acryloyloxyazobenzene copolymers are reported. Kinetics of photoinduced trans-cis and thermal cis-trans isomerization of azo pendant groups in copolymer have also been investigated, and the kinetic parameters were evaluated. An azo acrylate model compound was used for comparison.     

Coordination Polymers. 9. Chelate Polymers Derived from Bisphenolic Complexes and Propylenediamine

Chelate polymers derived from bis(2,4-dihydroxybenzaldehyde)propyl-enediimine M and bis(2,4-dihydroxyacetophenone)propylenediimine M (M = Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) with aromatic acid chlorides were prepared by interfacial polycondensation. Also, chelate polysiloxanes were obtained from the same monomers and α,ω-dichloropolydimethyl-siloxane. The spectral, thermal, magnetic, and electrical properties of the polychelates were studied.     

Enantioselective Extraction System Containing Binary Chiral Selectors and Chromatographic Enantioseparation Method for Determination of the Absolute Configuration of Enantiomers of Cyclopentolate

The distribution coefficients and enantioseparation of cyclopentolate were studied in an extraction system containing d-tartaric acid ditertbutyl ester in organic phase and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) in aqueous phase. Various parameters involved in the enantioseparation such as the type and the concentration of chiral selectors, pH value and a wide range of organic solvents were investigated. The maximum enantioselectivity (α = 2.13) and optimum distribution coefficients (K _R = 0.85, K _S = 0.40) were obtained under the following conditions: 0.10 mol/L HP-β-CD in aqueous phase and 0.20 mol/L d-tartaric acid ditertbutyl ester in decanol as organic phase. Cyclopentolate is present as a racemic mixture to the aqueous phase. The potentially different biological activities of cyclopentolate enantiomers have not been examined yet. Two chiral liquid chromatography methods have been developed for the direct separation of the enantiomers of cyclopentolate. First method was used for the quantification analysis of cyclopentolate enantiomers in aqueous phase. Second method used two chiroptical detectors: electronic circular dichroism (ECD) and optical rotation (OR) for the identification of individual cyclopentolate enantiomers from the organic phase enriched with (R)-enantiomer. The absolute stereochemistry was determined by means of the comparison of the experimental and computed ECD spectra and signs of OR. The ECD spectra of chiral analytes were measured on-line using HPLC-ECD technique.

     

Pinacol Rearrangement of 3,4‐Dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones: An Alternative Pathway to Viridicatin Alkaloids and Their Analogs

3‐Alkyl/aryl‐3‐hydroxyquinoline‐2,4‐diones were reduced with NaBH₄ to give cis‐3‐alkyl/aryl‐3,4‐dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones. These compounds were subjected to pinacol rearrangement by treatment with concentrated H₂SO₄, resulting in 4‐alkyl/aryl‐3‐hydroxyquinolin‐2(1H)‐ones. When a benzyl (Bn) group was present in position 3 of the starting compound, its elimination occurred during the rearrangement, and the corresponding 3‐hydroxyquinolin‐2(1H)‐one was formed. The reaction mechanisms are discussed for all transformations. All compounds were characterized by IR, ¹H‐ and ¹³C‐NMR spectroscopy, as well as mass spectrometry.     

Reaction of Some 2‐Quinolone Derivatives with Phosphoryl Chloride: Synthesis of Novel Phosphoric Acid Esters of 4‐Hydroxy‐2‐quinolone

3‐Chloroquinoline‐2,4‐diones do not react with phosphoryl chloride, however, 2,4‐dichloroquinolines and/or 4‐chloroquinolin‐2‐ones are formed in the presence of N,N‐dimethylaniline. Along with these compounds, small quantities of novel dihydrogen phosphates of 4‐hydroxyquinolin‐2‐ones were isolated. We outline a simple procedure that allows for the preparation of these compounds in moderate to good yields. All compounds were characterized by ¹H and ¹³C NMR, IR, EI‐MS, and ESI‐MS spectroscopy, and in select cases by ³¹P NMR spectroscopy.     

Catalytic Oxidative Cyclocondensation of o‐Aminophenols to 2‐Amino‐3H‐phenoxazin‐3‐ones

The catalytic oxidative cyclocondensation of the o‐aminophenols 1a–f was investigated. The oxidants used were air/laccase, H₂O₂/horseradish peroxidase, H₂O₂/ebselen (3), and TBHP/diphenyl diselenide 4. The products obtained were 2‐amino‐3H‐phenoxazin‐3‐one—questiomycin A, its derivative 2b, and cinnabarinic acid and actinocin (2c,d). Substrates with methyl groups at 4 and 5 positions of benzene ring were converted to different dihydrophenoxazinones 2g,h. Compounds having chlorine atoms at the same positions underwent oxidation to planar phenoxa-zinones 2e,f with elimination of one hydrochloride molecule.