bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of the Metabolic Degradation of an insect juvenile hormone analog using different radiolabeling
Authors: Tykva Richard , Wimmer Zdenêk , Bennettová Blanka , Vlasáková Vêra 
Published: December 2004

AbstractThe fate of an insect juvenile hormone analog applied to the insect body of the flesh fly (Sarcophaga bullata) or the tsetse fly (Glossina palpalis), respectively, was studied using three different radiolabeled positions in the parent biologically active compound 1. Several metabolites were found and analyzed. A mechanism of degradation of the applied molecule was designed using a combination of several radioanalytical methods. A unique monitoring of the applied compound and its metabolites was provided, based on the different radiolabeling of the structure (cf. 1a–1c), and established their fate in an insect body during a 10‐day experiment. A 14C and 3H radiolabeling, respectively, was employed to synthesize three different radiolabeled forms 1a–1c derived from the parent non‐labeled 1. A combination of three different ways of radiolabeling resulted in an advantage in tracing the metabolic pathway of degradation of the employed compound 1 in its radiolabeled forms 1a–1c.
Structure and Properties of Transition‐Metal Complexes with Chiral C2‐symmetric binucleating ligands
Authors: Fahrni Christoph J. , Pfaltz Andreas , Neuburger Markus , Zehnder Margareta 
Published: December 2004

AbstractThe coordination behavior of chiral binucleating ligands of type 1–4 with various transition metals has been investigated. 1H‐NMR Titration experiments with zinc(II) salts gave detailed structural information about the structure of the resulting zinc complexes. Ligand 1 forms an unusual C3‐symmetric dinuclear zinc complex [Zn2CIL3] (8a) which was characterized by X‐ray crystallography. Treatment of complex 8a with various carboxylic acids resulted in ligand‐exchange reactions. With ligand 2, a hydroxo‐bridged dinuclear copper complex 15 was synthesized and its structure elucidated by X‐ray analysis. Solution studies UV and 1H‐NMR spectroscopy of the reaction of ligand 3 with ZnII and NII salts revealed the formation of dimeric species of the type [M2X4L2]. Ligand 4 formed well‐defined dinuclear complexes with NiII and CuII salts of which the corresponding NiII complex [Ni2(AcO)2(ClO4)2L] (22a) was characterized by crystal‐structure analysis.
Synthesis and Biological Evaluation of 14‐Alkoxymorphinans. Part 15. Novel δ opiod receptor antagonists with high affinity and selectivity in the 14‐alkoxy‐substituted indolomorphinan series
Authors: Schmidhammer Helmut , Krassnig Roland , Greiner Elisabeth , Schütz Johannes , White Angela , Berzetei‐Gurske Ilona P. 
Published: December 2004

AbstractThe indolomorphinans 4–7 were prepared from their corresponding morphinan‐6‐one derivatives 8–11 via Fischer indole synthesis. Compounds 4 and 5 exhibited higher antagonist potency at δ opioid receptors in the mouse vas deferens preparation than the reference drug HS 378 (2), while compounds 6 and 7 were less potent.
Tetraepoxy[22]annulen(2.2.2.0): Ein neuartiges Tetraepoxy‐verbrücktes, neutrales, aromatisches [22]Annulen
Authors: Märkl Gottfried , Sauer Heinrich , Stiegler Jürgen , Kreitmeier Peter , Burgemeister Thomas 
Published: December 2004

Tetraepoxy[22]annulene(2.2.2.0): a Tetraepoxy‐Bridged Neutral Aromatic [22]Annulene of a New TypeWe describe the synthesis of tetraepoxy[22]annulene(2.2.2.0) 4, the first aromatic annulene of type B by a cyclizing twofold Wittig reaction of 2,2′‐bifuran‐5,5′‐dicarbaldehyde (5) and the bis[phosphonium] salt 8. The configuration of 4, mainly determined by NMR spectroscopy is (Z,E,Z). According to the UV/VIS spectrum and the 1H‐NMR data, the electronic situation in 4 is quite different from that of tetraepoxy[22]annulene(3.0.3.0) 2 and tetraepoxy[22]annulene(2.1.2.1) 3. According to variable‐temperature 1H‐NMR spectroscopy, 4 is a highly dynamic system, where the (E)‐double bond rotates around the adjacent σ‐bonds. At ca. −130°, this dynamic process is frozen, and 4 appears as a diatropic aromatic system; the free activation energy of the rotation ΔG≠ is ca. 8.75 kcal/mol.
Aminocyclopentitols from N‐Alkylpyridinium Salts: A photochemical approach
Authors: Acar Ersin A. , Glarner Fabrice , Burger Ulrich 
Published: December 2004

AbstractThe photolysis of N‐alkylpyridinium halides 9a–e in alkaline H2O gave 6‐azabicyclo[3.1.0]hexenol derivatives 10a–e. N–Substituents bearing ether, acetal, and alcohol functions were found to do not adversely influence the photochemical reaction course. The free OH groups of the N–(3‐hydroxypropyl) derivative 10d were protected by benzoylation. The ensuing dibenzoate 14 underwent stereocontrolled opening of the aziridine ring on reaction with MeSH/BF3 to give a thioether 15. With benzoic acid in CHCI3, 10d gave the 4‐hydroxy‐5‐aminocyclopent‐2‐enyl benzoate 11. The meso‐2‐aminocyclopent‐4‐ene‐1,3‐diol 12 was obtained by hydrolysis of 11. On reaction with Boc2O and NaI, the aziridine ring of 14 was converted to a bicyclic compound 17. Hydrolysis of 17 provided the trans‐1,3‐diol 18, the epimer of 12. Face‐selective dihydroxylation of Boc‐protected 12 gave a meso‐aminocyclopentanetetrol 23 which was characterized upon peracetylation. Dihydroxylation of 15 provided a racemic analogue of epi‐mannostatin A (26).
Asymmetric syn‐Dihydroxylation of β‐Substituted (2R)‐N‐(α,β‐Enoyl)bornane‐10,2‐sultams
Authors: Raczko Jerzy , Achmatowicz Michael , Jezewski Artur , Chapuis Christian , Urbañczyk‐Lipkowska Zofia , Jurczak Janusz 
Published: December 2004

AbstractVariously β‐substituted (2R)‐N‐[(E)‐α,β‐enoyl]bornane‐10,2‐sultams were oxidized with OsO4/4‐methylmorpholine 4‐oxide in a highly stereoselective manner. In all cases, the attack occurred on the C(α)‐re face. The absolute configurations of all products were determined by chemical correlation. Mechanistic considerations about the reactive conformation as well as fully refined X‐ray crystal structures of the dihydroxylated products are discussed. New neutral conditions for sultam acylation, applicable to the preparation of the taxol and Taxotere® C(13) side chain as well as of Cardizem® and chloramphenicol precursors, are also presented.
Nucleotides. Part LVI. Synthesis and biological activity of modified (2′–5′)triadenylates containing 2′‐terminal 2′,3′‐dideoxy‐3′‐fluoroadenosine derivatives
Authors: Kvasyuk Evgeny I. , Kulak Tamara I. , Tkachenko Olga V. , Sentyureva Svetlana L. , Mikhailopulo Igor A. , Suhadolnik Robert J. , Henderson Earl E. , Horvath Susan E. , Guan Ming‐Xu , Pfleiderer Wolfgang 
Published: December 2004

AbstractSome new (2′–5′)triadenylates 13–16, containing at the 2′‐terminal end 3′‐fluoro‐2′,3′‐dideoxyadenosine derivatives, have been synthesized by the phosphotriester method. The selectively blocked nucleosides 2, 4, 5, and 7, were synthesized from the corresponding unprotected nucleosides 1, 3, and 6. The synthesized trimers 13, and 14 were 4‐ and 8‐fold, respectively, more stable towards phosphodiesterase from Crotalus durissus than the natural trimer 17. In comparison to trimer 17 the new compounds 13–15 inhibit HIV‐1 reverse transcriptase (RT) activity, and 15 and 16 the HIV‐1 induced syncytia formation 2–3 fold whereas none of 13–16 can improve R Nase L activity.
Synthesis of the Spermidine Alkaloid (−)‐(4R)‐Dihydroisomyricoidine
Authors: Horni Albert , Linden Anthony , Hesse Manfred 
Published: December 2004

AbstractAn asymmetric synthesis of (−)‐(4R)‐dihydroisomyricoidine (28), a 13‐membered amino lactam of type A, was performed by a diastereoselective Michael addition between the spermidine derivative 3 and the commercially available optically active ethyl carboxylate 4, and the cyclization of the resulting ω‐amino acid 7 using diethyl phosphorocyanidate ((EtO)2POCN), followed by a Wittig reaction to introduce the (Z)‐side chain. Some side reactions are also discussed.
3‐Hydroxy‐2‐cyanoalk‐2‐enamides, and 2‐Cyano‐2‐(tetrahydrofuran‐2‐ylidene)‐ and 2‐Cyano‐2‐(tetrahydropyran‐2‐ylidene)acetamides: Synthesis, structure, and solvent‐dependent (Z)/(E)‐isomerism
Authors: Papageorgiou Christos , Akyel Kayhan , Borer Xaver , Oberer Lukas , Rihs Grety 
Published: December 2004

Abstract3‐Hydroxy‐2‐cyanoalk‐2‐enamides, and 2‐cyano‐2‐(tetrahydrofuran‐2‐ylidene)‐ and 2‐cyano‐2‐(tetrahydropyran‐2‐ylidene)acetamides with N‐alkyl and N‐aryl substituents have been synthesized in three steps from cyanoacetic acid. Their conformations were investigated by X‐ray crystallography and 1H‐NMR ROESY spectroscopy at room temperature. The enolic compounds 1–3 adopt an extended conformation stabilized by a strong intramolecular OH …︁ OC bond both in the solid state and in (D6)DMSO solution. In contrast, the structure of the cyclic derivatives 5a,b–8a,b is solvent‐dependent. In the solid state and in CDCl3 solution, the compounds adopt an extended conformation of type I or III, while, in (D6)DMSO solution, their structures undergo time‐dependent (Z)/(E)‐isomerization structures (of type II or IV). This observation is compatible with a dipolar transition state of rotation. The kinetics of the isomerization are controlled by the N‐substituent, the N‐(t‐Bu) derivatives 7a and 7b having the highest barrier of rotation around the CC bond. The whole body of experimental evidence together with the results of molecular‐mechanics calculations with I–IV, indicate that, in DMSO, two (E)/(Z)‐isomers with two conformations are present, and that they undergo interconversion at room temperature with four different constants. The very fast exchange rates kI,II and kIII,IV in the NMR time‐scale might be responsible for the detection of only two isomers.
1,2‐Carbonyl Transposition of a Protected Rubanone: Stereoselective synthesis of bicyclic and tricyclic lactams derived from quinidine
Authors: Frackenpohl Jens , Langer Peter , Hoffmann H. Martin R. 
Published: December 2004

Abstractα‐Bromination of 9‐acetoxy rubanone 2 and subsequent reaction with secondary amines gave bicyclic α‐amino ketones as a kinetic product and a 4‐oxa‐1‐azatwistan‐2‐one 6 under thermodynamic conditions. This two‐step procedure represents a concise 1,2‐carbonyl transposition and provides a short route to lactam alkaloids.
Nucleotides. Part LVII.. Synthesis of phosphoramidite building blocks of 2′‐amino‐2′‐deoxyribonucleosides: New compounds for oligonucleotide synthesis
Authors: Greiner Beate , Pfleiderer Wolfgang 
Published: December 2004

AbstractThe chemical synthesis of 2′‐amino‐2′‐deoxyribonucleosides of uracil, cytosine, adenine, and guanine, and their conversion into suitably protected 3′‐phosphoramidite building blocks 35–40 for oligonucleotide synthesis are described. The aglycone and the 2′‐amino functions were protected using the 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) group. The synthesis of the 3′‐O‐succinyl (3′‐O‐(3‐carboxypropanoyl))‐substituted starting nucleoside 41 is described and its behavior examined in solution and on solid phase with regard to an anticipated migration during 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) deprotection. Oligonucleotides were prepared using the new building blocks, and their hybridization properties were studied by UV‐melting techniques.
New prospects for a prolonged functional life‐span of artificial hip joints by using the material combination polyethylene/aluminium oxide ceramic/metal
Authors: Semlitsch M. , Lehmann M. , Weber H. , Doerre E. , Willert H. G. 
Published: December 2004

AbstractInvestigations over the years have shown that the mirror‐finished Al2O3 ceramic is a much more suitable frictional counterpart to ultrahigh molecular weight (UHMW) polyethylene than metal. Despite the extremely great hardness difference between polyethylene and Al2O3 ceramic, a considerable lower wear rate is obtained for the polyethylene socket with this new low‐friction material combination. The unexpectedly favorable tribological behavior of this ceramic material in contact with polyethylene may be attributed to the following factors: better values for corrosion resistance characteristics, wettability with liquids, surface gloss, hardness, and scratch resistance of the ceramic material in comparison with those of the hitherto used metallic implant materials (AISI‐316L steel or cast CoCrMo alloy). It appears that, by using this new combination of materials for the socket and the ball, it will be possible to prolong the service life of artificial hip joints considerably without having to effect any fundamental changes in the present design and implantation principle retaining the hitherto used anchorage shaft made of wrought CoNiCrMoTi alloy Protasul‐10 of extremely high corrosion fatigue strength.
Cellulosic ion‐exchange membranes for hemodialysis
Authors: Mollison A. N. , Graydon W. F. 
Published: December 2004

AbstractThe application of cellulosic ion‐exchange membranes to hemodialysis was studied in vitro. The membranes were prepared by radiation‐grafting methacrylic acid and vinylpyridine to films of DuPont cellophane PD‐215 to produce cation‐exchange and anion‐exchange membranes, respectively.Solutions of urea, creatinine, glucose, and uric acid were studied for their interactions with and diffusion through the membranes. Ultrafiltration rates were also determined. Cuprophane and PD‐215 cellophane were studied as controls.Dialysis plots for the membranes revealed a mechanism of “assisted transport”. Initially, the solutes were removed from solution by a sorption/adsorption mechanism followed by a steady‐state diffusion process. The calculated diffusivities for these later steady‐state regions increased linearly with capacity for urea, creatinine, and uric acid, while for glucose the reverse was true.The combined processes involved provided considerably greater mass transport per unit thickness than either DuPont PD‐215 cellophane or Cupropane.
Maxillofacial prostheses of chlorinated polyethylene
Authors: May P. D. , Guerra L. R. 
Published: December 2004

AbstractThere is clearly a need for maxillofacial prosthetic materials with improved properties. The chlorinated polyethylenes are thermoplastic elastomers which have particularly promising properties, and were used by us to prepare improved maxillofacial prostheses. Suitable CPE resins were compounded with other polymers and with pigments on a heated rubber mill to form thin sheets in a variety of shades. These were heated at 190°C for 10 min and placed between heated linotype mold halves. The prosthesis was formed in a hand press. Sometimes heating and pressing were repeated. After cooling in water, the prosthesis was removed and hand‐shaded with oil‐soluble dyes. Physical properties were evaluated using standard techniques; skin irritation studies were conducted by 14‐day insult patch tests on rabbits. Clinical evaluations were conducted on human volunteers. Parallel evaluations were conducted on commercially available materials for comparison. The CPE was superior to all of the three commercial materials in most properties, and comparable to the better of the three in the remaining properties. On balance, CPE was significantly superior. Early results indicate that the materials and techniques required are easily handled in the dental lab and that the final prosthesis has excellent aesthetic and patient acceptability.
A high‐modulus polymer for porous orthopedic implants: Biomechanical compatibility of porous implants
Authors: Spector M. , Michno M. J. , Smarook W. H. , Kwiatkowski G. T. 
Published: December 2004

AbstractA high‐modulus polymer, polysulfone, was evaluated as a porous bone implant material. The bone ingrowth into canine cortical pellets of sintered polysulfone particles was assessed by microradiography and histology. The shear strength of the porous polysulfone–bone interface was determined by push‐out and pull‐out tests of cortical and trochanteric implants, respectively. Results indicated that the bone in‐growth into porous polysulfone specimens proceeded in such a fashion as to mimic the normal repair at the site. Mechanical testing of cortical and cancellous implants revealed that the interfacial shear strength of the porous polysulfone‐bone composite was similar to that achieved using porous metals.
The rate of adhesion of melanoma cells onto nonionic polymer surfaces
Authors: Yasuda H. , Yamanashi B. S. , Devito D. P. 
Published: December 2004

AbstractThe rates of adhesion of melanoma cells (carcinogenic) onto nonionic polymer surfaces were studied by using radioactively labeled cells and measuring the fraction of cells which adhered to the surface in a given time. Glow discharge (plasma) polymerization of 1,1,3,3‐tetramethyldisiloxane and of nitrogen‐acetylene‐water (mole ratio 0.4:1.0:0.2) was used to modify the surface energy of the substrate. The cell adhesion rate was found to be given by Y = 1 − exp [−k0(γs − γ0)t], where Y is the fraction of cells adhered, − k0 is a characteristic rate constant, γs is the total surface energy of the substrate, γ0 is the threshold surface energy of cell adhesion, and t is time.
Corrosion behavior of cast and forged cobalt‐based alloys for double‐alloy joint endoprostheses
Authors: Süry P. , Semlitsch M. 
Published: December 2004

AbstractAn ideal combination of mechanical and corrosion properties of long‐term implants such as joint endoprostheses has yet to be found. Besides being resistant to pitting and crevice attack, which can lead to corrosion fatigue and stress corrosion cracking failures, the implant material must be highly resistant to wear and abrasion. Two cobalt‐based alloys, wrought CoNiMoTi and air‐cast CoCrMo, were subjected to a number of selected in vitro electrochemically and chemically accelerated corrosion tests in chloride‐containing solutions with wrought AISI‐316L used as a reference alloy. A limited number of immersion tests in FeCl3 and acidified FeCl3 solutions were also conducted. It is found that the mechanical properties of wrought CoNiCrMoTi alloy qualify it as a substitute for cast CoCrMo alloy and wrought AISI‐316L in anchorage shaft production for all types of joint endoprostheses. Wrought CoNiCrMoTi has a higher resistance to fatigue cracking compared with cast CoCrMo and is as resistant to selective corrosion phenomena such as stress corrosion cracking.
Measurement of the rate of wear of dental composite resins by a 90Sr beta particle transmission gauge
Authors: Moores G. E. , Glentworth P. , Harrison A. 
Published: December 2004

AbstractThe wear rate of restorative dental composite resins is an important parameter in the assessment of their in vivo performance. The two more widely used methods of quantifying wear are measuring the dimensional change and measuring the change in the mass of the specimen. The former method is complicated by uneven wear of specimens and presents difficulties with samples of irregular shape, and the latter method involves measurements of changes in mass as small as tens of micrograms with specimens of sizes similar to those encountered clinically. A 90Sr beta particle transmission gauge has been designed and constructed to enable the wear rate of small specimens of dental composite resins to be measured. The 90Sr beta particle transmission gauge enables indirect measurements of changes in mass to be made and overcomes some of the difficulties inherent in the direct measurement of mass and length. Applications of the 90Sr beta particle transmission gauge to the measurement of wear rates are given for restorative dental resins having a range of inorganic filler contents and types. The results show that the 90Sr beta particle transmission gauge is capable of measuring the rate of wear to a degree of precision similar to that of micrometer‐derived measurements.
Macroporous hydrogel membranes for a hybrid artificial pancreas. I. Synthesis and chamber fabrication
Authors: Ronel Samuel H. , D'Andrea Mark J. , Hashiguchi Hiroshi , Klomp Gregory F. , Dobelle William H. 
Published: December 2004

AbstractWe report development of special macroporous semipermeable membranes and diffusion chambers made of polymerized 2‐hydroxyethyl methacrylate (pHEMA), synthesized specifically to enclose living insulin‐producing pancreatic islet cells for the treatment of diabetes. This material was selected to minimize the fibrotic encapsulation which has limited hybrid artificial pancreas efforts with other membranes, including Millipore and Nuclepore filters. The pore density and pore size distribution were dependent on the ratio of water to HEMA monomer and also on the crosslinker (EGDMA) concentration. A macroporous membrane resulted only when the ratio of water/HEMA monomer was greater than 50%. 125I‐insulin permeability was studied in vitro. A technique is also described to fuse the membranes to form diffusion chambers used for implantation into diabetic rats.
The retention mechanics of LTI carbon, carbon‐coated aluminum oxide, and uncoated aluminum oxide dental implants
Authors: Cook S. D. , Weinstein A. M. , Klawitter J. J. 
Published: December 2004

AbstractThe in vitro mechanical behavior of identical geometry LTI carbon, carbon‐coated aluminum oxide, and uncoated aluminum oxide blade‐type dental implants has been evaluated using rosette type strain gauges and a LVDT system. The implants served as a distal abutment for a three‐unit fixed prosthesis and functioned for a period of 2 years in female baboons. The comparison of the LTI carbon implants to the carbon‐coated aluminum oxide implants allowed for a study of the effect of implant elastic modulus on the mechanical behavior, while the comparison of the carbon‐coated and uncoated aluminum oxide implants allowed for a study of the effect of chemical composition at the tissue–implant interface. The results of the mechanical testing indicate that the implant displacement response of the LTI carbon implants was greater than that of the carbon‐coated and uncoated aluminum oxide implants. Little difference in displacement response was observed for the carbon‐coated and uncoated aluminum oxide implants. No clear trend in the strain response of the buccal mandibular bone was observed for the three implant systems. The greatest differences in strain response, however, was observed between the uncoated aluminum oxide implants and the LTI carbon and carbon‐coated aluminum oxide implants.
Supermolecular organization of some polyurethanes containing sugar derivatives in the main chain
Authors: Lipatova T. E. , Pkhakadze G. A. , Snegirev A. I. , Vorona V. V. , Shilov V. V. 
Published: December 2004

AbstractX‐ray studies on polyurethanes containing sugar derivatives in the main chain were performed. It was demonstrated that the microphase separation of rigid and flexible fragments was dependent on the nature of sugar derivatives. The supermolecular organization in disaccharide‐based polymers is the most ordered one. In xylose‐ and arabinose‐based polyurethanes the phase separation is defined least of all. Glucose‐ and dulcitol‐based polymers are intermediates as to their supermolecular organization. Supermolecular organization models for block copolyurethanes under investigation were proposed.