<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Synthesis of Novel <Emphasis Type="Italic">D</Emphasis>-<Emphasis Type="Italic">Seco</Emphasis>-Pregnenes

Summary. A new synthetic route was developed for the preparation of trans-3-hydroxy-16,17-seco-pregna-5,17(20)-dien-16-al, using Grob fragmentation as the key step. This seco-steroid contains a formyl group and an unsaturated side-chain in a sterically favourable position, and is therefore a promising starting material for the synthesis of novel condensed steroid heterocycles.Received March 22, 2003; accepted April 22, 2003 Published online September 25, 2003     

Conformational Polymorphism in Racemic 2,4-Di-<Emphasis Type="Italic">o</Emphasis>-Benzoyl-6-<Emphasis Type="Italic">o</Emphasis>-Tosyl <Emphasis Type="Italic">myo</Emphasis>-Inositol 1,3,5-Orthoacetate

The title compound, C₂₉H₂₆O₁₀S, yields two conformational polymorphs concomitantly from dichloromethane-methanol mixture; the major polymorph grows as plates (Form I, monoclinic, P2₁/n) and the minor polymorph grows as needles (Form II, triclinic, P-1). The two forms differ mainly in orientation of the tosyl group. In Form I, sulfonyl oxygen of the tosyl group makes intermolecular C −H…O interactions, whereas the same group in Form II is involved in an intramolecular short dipolar S=O…C=O (sulfonyl-carbonyl) contact. The molecular organization and the influence of various weak non-covalent interactions that stabilize these conformers in the crystal lattices are discussed.     

Structure of <Emphasis Type="Italic">peri</Emphasis>-hydroxy- and <Emphasis Type="Italic">peri</Emphasis>-methoxy-substituted aldehydes and ketones according to spectral data and quantum-chemical calculations

The structure of peri-hydroxy- and peri-methoxy-substituted aldehydes and ketones of the naphthalene, acenaphthene, and acenaphthylene series and the nature of intramolecular interactions between the peri- substituents therein were determined by spectral (IR, UV, 1H NMR), X-ray diffraction, and quantum-chemical methods.     

Mono-<Emphasis Type="Italic">meso</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylporphyrin

Summary. Treatment of meso-tetra(tert-butyl)porphyrin with sulfuric acid/n-butanol affords a mixture of porphyrin and mono-tert-butylporphyrin in relatively high yield.     

Molecular properties of the copolymers of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride and maleic acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.     

Rapid SnCl<Subscript>2</Subscript> catalyzed phenylselenoetherification of (<Emphasis Type="Italic">Z</Emphasis>)- and (<Emphasis Type="Italic">E</Emphasis>)-hex-4-en-1-ols

A fast and efficient method for intramolecular heterocyclization of (Z)- and (E)-hex-4-en-1-ols was developed. The method does not cause side reactions of the substrates and provides the cyclic phenylselenoethers in high yields after only few minutes. A catalytic amount of SnCl₂ increased the yield, but in the presence of an equimolar amount of SnCl₂, formation of corresponding cyclic ethers were almost quantitative and reaction occurred instantaneously under extremely mild experimental conditions. Correspondence: Zorica M. Bugarčić, Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, P.O.Box 60, YU-34000 Kragujevac, Serbia.     

Thiocyanation of <Emphasis Type="Italic">N</Emphasis>-arylsulfonyl-, <Emphasis Type="Italic">N</Emphasis>-aroyl-, and <Emphasis Type="Italic">N</Emphasis>-[(<Emphasis Type="Italic">N</Emphasis>-arylsulfonyl)benzimidoyl]-1,4-benzoquinone imines

Reactions of thiocyanate ion with N-aroyl-, N-arylsulfonyl-, and N-(N-arylsulfonylbenzimidoyl)-1,4-benzoquinone imines follow the 1,4-addition pattern, and the adducts undergo intramolecular cyclization to give the corresponding N-substituted 5-amino-1,3-benzoxathiol-2-ones as final products.     

Antioxidant flavonoids from <Emphasis Type="Italic">Tamus communis</Emphasis> ssp. <Emphasis Type="Italic">cretica</Emphasis>

A new flavonoid, kaempferol-3,4′-di-O-α-L-rhamnopyranoside (1), and three known flavonoids (2–4) were isolated from the aerial parts of T. communis L. The structure of the new compound was elucidated on the basis of spectroscopic data. Compounds 1 and 2 showed significant antioxidant activity (IC₅₀ 187.151 ± 0.821 μM, and 92.079±0.513 μM, respectively), whereas compounds 3 and 4 showed moderate activity in DPPH free radical scavenging assays. Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 295–297, May–June, 2009.     

Molecular structure of <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">o</Emphasis>-and <Emphasis Type="Italic">p</Emphasis>-hydroxybenzyl)cytisine

The molecular structures of N-(o-and p-hydroxybenzyl)cytisine were investigated by NMR spectroscopy, x-ray structure analysis, and molecular modeling. It was found that NMR resonances of the OH and aromatic protons in N-(o-hydroxybenzyl)cytisine were doubled because of the presence of two conformers in solution. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 165–168, March–April, 2008.     

Cyclofunctionalization of 6-alkenylsulfanylpyrazolo[3,4-<Emphasis Type="Italic">d</Emphasis>]-pyrimidin-4(5<Emphasis Type="Italic">H</Emphasis>)-ones with arenesulfenyl chlorides

Reactions of 6-allylsulfanylpyrazolo[3,4-d]pyrimidin-4(5H)-one with arenesulfenyl chlorides in chloroform gave products of addition of the latter at the exocyclic double bond, while analogous reactions in acetic acid in the presence of LiClO₄ were accompanied by intramolecular electrophilic cyclization involving the N⁷ atom. 6-Cinnamylsulfanylpyrazolo[3,4-d]pyrimidin-4(5H)-one reacted with arenesulfenyl chlorides in acetic acid in the absence of electrolyte to produce fused pyrazolo[4′,3′: 5,6]pyrimido[2,1-b][1,3]thiazine derivatives. Introduction of a bulky phenyl group into position 1 of the pyrazolo[3,4-d]pyrimidine system reduces the yield of the corresponding intramolecular cyclization product at N⁷ as a result of concurrent formation of acyclic addition product. DOI     

<Emphasis Type="Italic">seco</Emphasis>-Kaurane skeleton diterpenoids from <Emphasis Type="Italic">Croton oblongifolius</Emphasis>

A new seco-kaurane type diterpenoid, ent-3,4-seco-17-oxo-kaur-4(19),15(16)-dien-3-oic acid, and a known compound, ent-3,4-seco-kaur-4(19),16(17)-dien-3-oic acid, were isolated from the stem bark of Croton oblongifolius. The structures of these compounds were established on the basis of spectroscopic data.     

Analysis of <Emphasis Type="Italic">Escherichia coli</Emphasis> nicotinate mononucleotide adenylyltransferase mutants <Emphasis Type="Italic">in vivo</Emphasis> and <Emphasis Type="Italic">in vitro</Emphasis>

Background  

Adenylation of nicotinate mononucleotide to nicotinate adenine dinucleotide is the penultimate step in NAD⁺ synthesis. In Escherichia coli, the enzyme nicotinate mononucleotide adenylyltransferase is encoded by the nadD gene. We have earlier made an initial characterization in vivo of two mutant enzymes, NadD72 and NadD74. Strains with either mutation have decreased intracellular levels of NAD⁺, especially for one of the alleles, nadD72.     

Spectral and quantum-chemical investigation of <Emphasis Type="Italic">ortho</Emphasis>- and <Emphasis Type="Italic">peri</Emphasis>-hydroxy-substituted mono- and diformyl derivatives of 1,5-naphthalenediol

Spectral and quantum-chemical investigation of ortho- and peri-hydroxy-substituted aldehydes, 1,5-naphthalenediol derivatives, was carried out. An unusual spin-spin coupling through an intramolecular hydrogen bond was discovered in the molecule of 1,5-dihydroxynaphthalene-4,8-dicarbaldehyde. It was shown that this dialdehyde is involved into the ring-chain tautomerism. The position of this equilibrium was examined depending on the temperature and the solvent polarity. The effect of the solvent polarity on the benzoid-quinoid tautomerism in the dihydroxynaphthalene-2,6-dicarbaldehyde was established. By the method of quantum-chemical calculations the relative energy stability and conformational structure of dialdehydes were revealed.     

New lignans from <Emphasis Type="Italic">Syringa reticulata</Emphasis> var. <Emphasis Type="Italic">mandshurica</Emphasis>

In the search for platelet-activating-factor (PAF) antagonists, two new lignan compounds were isolated from the leaves of Syringa reticulata Hara var. mandshurica. Their structures were elucidated as (7R,8S, 8'S)-3,4,3',4'-dimethylenedioxy-8,9-dihydroxy-8.8', 7-O-9'-lignan (mandshuricol A) and (7R,8S,8'S)-3',4'methylenedioxy-4-methoxy-3,8,9-trihydroxy-8.8', 7-O-9'-lignan (mandshuricol B), Mandshuricol A and B showed antagonistic activity on PAF in the [³H] PAF receptor binding assay with IC₅₀ values of 4.8 × 10^–5 M and 3.5 × 10^–5 M, respectively.     

Screening and Immobilization <Emphasis Type="Italic">Burkholderia</Emphasis> sp. GXU56 Lipase for Enantioselective Resolution of (<Emphasis Type="Italic">R</Emphasis>,<Emphasis Type="Italic">S</Emphasis>)-Methyl Mandelate

Microorganisms producing lipase were isolated from soil and sewage samples and screened for enantioselective resolution of (R,S)-methyl mandelate to (R)-mandelic acid. A strain designated as GXU56 was obtained and identified as Burkholderia sp. Preparing immobilized GXU56 lipase by simple adsorption on octyl sepharose CL-4B, the optimum temperature was shifted from 40 °C (free lipase) to 50 °C (immobilized lipase), and the optimum pH was shifted from 8.0 (free lipase) to 7.2 (immobilized lipase). The immobilized enzyme displayed excellent stability in the pH range of 5.0–8.0, at the temperatures below 50 °C and in organic solvents compared with free enzyme. Enantioselectivity ratio for (R)-mandelic acid (E) was dramatically improved from 29.2 to more than 300 by applying immobilized lipase in the resolution of (R,S)-methyl mandelate. After five cycles of use of immobilized lipase, conversion and enantiomeric excess of (R)-mandelic acid were 34.5% and 98.5%, respectively, with enantioselectivity ratio for (R)-mandelic acid (E) of 230. Thus, octyl-sepharose-immobilized GXU56 lipase can be used as a bio-resolution reagent for producing (R)-mandelic acid.     

Isolation and characterization of the cellulose synthase genes <Emphasis Type="Italic">PpCesA6</Emphasis> and <Emphasis Type="Italic">PpCesA7</Emphasis> in <Emphasis Type="Italic">Physcomitrella patens</Emphasis>

Analysis of cellulose biosynthesis using molecular approaches has been successful in identifying genes in many cellulose-producing organisms, yet the mechanism of cellulose biosynthesis still remains to be understood. We are interested in developing the moss Physcomitrella patens as a useful system for the study of cellulose biosynthesis. This moss affords a number of advantages including a haploid dominated gametophyte and a very high efficiency of homologous recombination in its nuclear DNA for constructing gene knockouts. In addition, P. patens has only a primary cell wall unlike Arabidopsis thaliana, which has both a primary and a secondary cell wall. We identified two full-length cellulose synthase (CesA) genes of P. patens, PpCesA6 and PpCesA7 from an EST database and have analyzed the genomic sequences. PpCesA6 and PpCesA7 show high similarity to each other, both at the cDNA and genomic DNA levels. Single and double knockouts of PpCesA6 and PpCesA7 were generated and screened for phenotypic changes. While the PpCesA6 and PpCesA7 single knockouts did not show any obvious phenotypic differences from the wild-type, the double knockout had significantly reduced stem length. These results suggest that PpCesA6 and PpCesA7 probably have a very similar role in cellulose biosynthesis and their functions may be redundant. Additionally, their roles may overlap with the other P. patens CesAs as observed for CesAs involved in primary cell wall biosynthesis in A. thaliana.     

Synthesis of <Emphasis Type="Italic">o</Emphasis>(<Emphasis Type="Italic">m</Emphasis>)-carborane-containing azomethines

A method of preparative synthesis of o(m)-carborane-containing azomethines via the condensation of o(m)-carboranyl-C-methylene-4-formylbenzoates with aliphatic, cycloaliphatic, and aromatic amines was developed.     

Synthesis of <Emphasis Type="Italic">N,N</Emphasis>-disubstituted (<Emphasis Type="Italic">Z</Emphasis>)-<Emphasis Type="Italic">O</Emphasis>-methylnicotinamide oximes

A number of (Z)-N,N-dialkyl- and (Z)-N-acyl-N-alkyl-O-methylnicotinamide oximes was synthesized. Their configuration was confirmed by the NOESY experiment. Evaluation of fungicidal activity of compounds obtained was performed.     

4<Emphasis Type="Italic">p</Emphasis><Superscript>2</Superscript> resonances in photoionization from 4<Emphasis Type="Italic">s</Emphasis>4<Emphasis Type="Italic">p</Emphasis> levels in neutral zinc

In neutral zinc the 4p ² configuration lies above the 3d ¹⁰4s ionization limit and its levels become perturbers in the continuum. Lines have been identified in the Zn I spectrum for the multiplet, whereas no lines have been found for transitions to 4p ^{2 1} D or ¹ S. In this paper, cross sections for photoionization from 4s4p levels are reported that reveal the positions and widths of the 4p ² resonances. Calculations were performed using the multiconfiguration Hartree-Fock (MCHF) and B-spline R-matrix (BSR) method. Results from Breit–Pauli calculations that ignore the background continua are also presented. Included in the latter are energies for the levels and transition data (transition energies, line strengths, f-values, and A-rates) for all E1 transitions between these levels. Transition energies and the agreement in the length and velocity values, particularly for allowed transitions, indicate the accuracy of the computational model. Line widths are compared with other estimates. Contribution to the Serafin Fraga Memorial Issue.