bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biocatalytic Deracemization of 1,4‐Benzodiazepines in the Synthesis of Enantiomerically Pure Serine
Authors: Avdagić Amir , Šunjić Vitomir 
Published: December 2004

AbstractAn efficient stereocontrolled synthesis of (S)‐N‐Cbz‐serine (Cbz = benzyloxycarbonyl; 12) and of its (R)‐enantiomer is reported. Kinetic resolution of the easily available racemic 3‐(hydroxymethyl)‐1,4‐benzodiazepin‐2‐ones is performed in the key step via acetylation by the immobilized Mucor miehei lipase (Lipozyme IM) at 60°. This method is characterized by high enantiomer purity (ee's ges; 99%) of the intermediary alcohols (+)‐8 and (+)‐9 and acetates (−)‐10 and (−)‐11, as well as of the final products (S)‐ and (R)‐N‐Cbz‐serine, simple recycling of the biocatalyst, complete recovery of 2‐aminobenzophenones (3 and 4) and their recycling into production of 1,4‐benzodiazepines, and possibility to selectively racemize ‘wrong’ enantiomers of the alcohols 8 and 9 in the presence of Amberlite CG 400.
Synthesis of New Nucleosides by coupling of chloropurines with 2‐ and 3‐deoxy derivatives of N‐methyl‐D‐ribofuranuronamide
Authors: Volpini Rosaria , Camaioni Emidio , Vittori Sauro , Barboni Luciano , Lambertucci Catia , Cristalli Gloria 
Published: December 2004

AbstractThe synthesis of new deoxyribose nucleosides by coupling chloropurines with modified D‐ribose derivatives is reported. The methyl 2‐deoxy‐N‐methyl‐3‐O‐(p‐toluoyl)‐α‐D‐ribofuranosiduronamide (α‐D‐8) and the corresponding anomer β‐D‐8 were synthesized starting from the commercially available 2‐deoxy‐D‐ribose (1) (Scheme 1). Reaction of α‐D‐8 with the silylated derivative of 2,6‐dichloro‐9H‐purine (9) afforded regioselectively the N9‐(2′‐deoxyribonucleoside) 10 as anomeric mixture (Scheme 2), whereas β‐D‐8 did not react. Glycosylation of 9 or of 6‐chloro‐9H‐purine (17) with 1,2‐di‐O‐acetyl‐3‐deoxy‐N‐methyl‐β‐D‐ribofuranuronamide (13) yielded only the protected β‐D‐anomers 14 and 18, respectively (Scheme 3). Subsequent deacetylation and dechlorination afforded the desired nucleosides β‐D‐11, β‐D‐12,15, and 16. The 3′‐deoxy‐2‐chloroadenosine derivative 15 showed the highest affinity and selectivity for adenotin binding site vs. A1 and A2A adenosine receptor subtypes.
Synthesis of Chiral C2‐Symmetric Binucleating Ligands
Authors: Fahrni Christoph J. , Pfaltz Andreas 
Published: December 2004

AbstractThe synthesis of a series of chiral enantiomerically pure C2‐symmetric binucleating ligands is reported. Ligands of type 1–4, which consist of a phenolic or heterocyclic unit bridging two chiral dihydrooxazole rings. are readily accessible from chiral amino alcohols. Ligands 5a and 5b are composed of a cyclic urea or thiourea unit, respectively, and two 3,4‐dihydro‐2H‐pyrrole rings containing a stereogenic center next to the N‐atom. Compounds of this type are readily assembled from ethane‐1,2‐diamine and an imidothioic ester derived from pyroglutamic acid. These new ligands, which can coordinate two metals in close proximity to each other, are of interest regarding possible applications in asymmetric catalysis.
First Preparative Enantiomer Resolution of Pirlindole, a Potent Antidepressant Drug
Authors: de Tullio Pascal , Felikidis Apostolos , Pirotte Bernard , Liégeois Jean‐François , Stachow Monique , Delarge Jacques , Ceccato Attilio , Hubert Philippe , Crommen Jacques , Géczy Joseph 
Published: December 2004

AbstractPirlindole is an antidepressant drug. It acts principally as reversible inhibitor of monoamine oxidase‐A (RIMA) and appears relatively potent in comparison with reference drugs. Pirlindole possesses stereogenic center but is generally used as racemate. In this work, the first preparative resolution of its enantiomeric couple is described. Whereas selective crystallization of salts of chiral acid failed, two asymmetric synthetic pathways were also examined; however, without success. Finally separation and isolation of enantiomers of pirlindole was completed by using the derivatization method coupled with preparative HPLC. Optical purity of each isomer was determined by chiral HPLC. The specific rotation of each antipode was also determined.
Induction of an Enantiomeric Excess in a Calix[4]arene/Bipyridine‐Based chiral copper(i) complex
Authors: Regnouf‐de‐Vains Jean‐Bernard , Lamartine Roger , Fenet Bernard 
Published: December 2004

AbstractIntroduction of the non‐complexing chiral (S)‐2‐methylbutoxy substituent close to the complexing site of a bis[(bipyridinyl)methoxy]calixarene podand resulted in the induction of an enantiomeric excess of ca. 30 % in the corresponding chiral CuI complex. Structural investigations by high‐resolution NMR studies led us to propose the left‐handed prohelical [CuI(bpy)2] substructure for the major enantiomer.
Enantioselective Dicarbonylation of Styrene to Isotactic Poly[1‐oxo‐2‐phenylpropane‐1,3‐diyl] with phosphinodihydrooxazole‐palladium(ii) complexes: Model studies for enantioface selection preliminary communication
Authors: Aeby Anton , Bangerter Felix , Consiglio Giambattista 
Published: December 2004

AbstractThe first steps, believed to be involved in the highly enantioselective copolymerization of styrene and carbon monoxide to poly[1‐oxo‐2‐phenylpropane‐1,3‐diyl] with phosphinodihydrooxazole‐palladium(II) complexes, were investigated. The insertion of carbon monoxide into [Pd(Me)(PˆN)(solvent)] TfO (PˆN = (S)‐2‐[2‐(5H‐benzo[b]phosphindol‐5‐yl)phenyl]4‐benzyl‐4,5‐dihydrooxazole (1)) and of styrene into [Pd(Me)(PˆN)(solvent)] TfO were highly regioselective (alkyl and acyl substituents trans to N); moreover, the olefin insertion took place with essentially complete enantioface discrimination.
Stereochemistry of the Inhibition of δ‐Chymotrypsin with Optically Active cis‐Decaline‐Type Organophosphates: 31P‐NMR studies
Authors: Furegati Stefan , Ganci Walter , Przibille Georg , Rüedi Peter 
Published: December 2004

AbstractInvestigation of the inhibition of δ‐chymotrypsin with the four novel, optically active, axially and equatorially substituted cis‐3‐(2,4‐dinitrophenoxy)‐2,4‐dioxa‐3λ5‐phosphabicyclo[4.4.0]decan‐3‐ones (= 3‐(2,4‐dinitrophenoxy)hexahydro‐4H‐1,3,2‐benzodioxaphosphorin 2‐oxides) showed only the equatorially substituted enantiomer (−)‐4b to be an irreversible inhibitor of the enzyme, and (−)‐4b at pH 7.8 revealed a quickly rising resonance at −2.49 ppm assigned to the hydrolysis product 8 and later, while inhibition proceeded, a second one at −4.08 ppm. attributed to the δ‐chymotrypsin adduct 7 (Scheme 3). Comparision of the latter signal with the 31P‐NMR chemical shifts of the covalent phosphoserine model compounds (−)‐6a (−5.67 ppm, axial substitution) and (+)‐6b (−4.02 ppm, equatorial substitution) suggests that the inhibition proceeded via neat retention of the configuration at the P‐atom of (−)‐4b yielding the equatorially substituted covalent Ser195 adduct 7.
Monoterpene Dimers from Lisianthius seemannii
Authors: Rodriguez Sylvain , Wolfender Jean‐Luc , Hostettmann Kurt , Stoeckli‐Evans Helen , Gupta Mahabir P. 
Published: December 2004

AbstractA new acylated dimeric secoiridoid glycoside, seemannoside A (2), has been isolated from the aerial parts of Lisianthius seemannii (GRISEB) O. KUNTZE (Gentianaceae). The structure was established by spectroscopic analysis (UV, MS, 1H‐ and 13C‐NMR, and 2D‐NMR experiments) and chemical reactions as (E‐4′‐O‐p‐coumaroyl)lisianthioside. The structure of the (Z)‐isomer (seemannoside B, 3), also present in the plant, was confirmed by LC/UV/1H‐NMR analysis. The active principle, 6, responsible for the antifungal activity of the apolar extract against Cladosporium cucumerinum, has been isolated. Its structure has been established by NMR spectroscopy and X‐ray crystallographic analysis as a rare type of aglycone monoterpene dimer.
Progress in splat‐cooling of dental alloys
Authors: Johnson L. B. , Carwile A. C. 
Published: December 2004

AbstractImproved techniques in preparing and sizing dental alloy powders containing Ag, Sn, and Cu have led to amalgams with higher strengths and less spread in dimensional change but very poor shelf life. Since maximum strengths occurred for amalgams containing about 15% more Sn than previously reported, and consequently presumably more of the weak γ2 phase, the higher strengths are difficult to understand.The poor shelf life may be explained by oxidation of the highly reactive splatcooled alloy or possibly by the existence of highly reactive metastable phases which transform fairly rapidly to the less reactive equilibrium ones.
Crevice corrosion in orthopedic implant metals
Authors: Levine D. L. , Staehle R. W. 
Published: December 2004

AbstractStudies of orthopedic implant alloys in crevice configuration suggest that cobalt‐chromium alloys such as Haynes‐Stellite 25 are the best choice for multicomponent implants. It is also shown that severe crevice attack may result from use of mixed metals.
Fracture characteristics of acrylic bone cements. II. Fatigue
Authors: Freitag Thomas A. , Cannon Stephen L. 
Published: December 2004

AbstractThe vital first phase of the overall materials study to protract the life of total joint replacements is the identification of the fracture toughness and fatigue properties of bone cements. Information gained from fatigue testing, performed in a manner which simulates in vivo conditions, and fracture toughness, which is a measure of the propensity of a crack to propagate, is the first step towards the prediction of the life of the total joint replacement. Part I of this study identified the fracture toughness characteristics of two acrylic bone cements, while the present work has been concerned with determining the fatigue behavior by means of tests conducted in a rotating bending fatigue apparatus. Fatigue specimens were fabricated under conditions which approximated clinical procedures and then tested while immersed in bovine serum at 37°C in order to simulate in vivo conditions. In addition, a similar study was completed on specimens tested in air at ambient temperature for purposes of comparison. Testing was conducted in both of these environments on specimens containing zero and 10.0 wt % BaSO4. Cyclic loading frequency was maintained between 1200 and 1400 cycles/min in order to insure that crack propagation was the sole mechanism of failure, i.e., failure via cyclic thermal softening was obviated.Results of this phase of the study, when analyzed by a Student t‐test at the 90% confidence level with four degrees of freedom, indicate that the fatigue life of specimens tested in bovine serum at 37°C is superior to that of specimens tested in air at ambient temperature. The addition of BaSO4 to Simplex‐P cement, while not significant at the 90% confidence level, was significant in increasing the fatigue life in air at the 80% confidence level; however, this effect was not noticeable when testing in bovine serum at 37°C. Examination of the fracture surfaces enabled calculation of the critical stress intensity factor which when compared with values from an earlier work showed good agreement.
Collagen sponge: Theory and practice of medical applications
Authors: Chvapil Milos 
Published: December 2004

AbstractTheoretical as well as practical–clinical applications of one form of collagen (collagen sponge) as a biodegradable material is reviewed. The role of porosity of the sponge and surface characteristics of the meshwork in relation to cell ingrowth are considered essential features of collagen sponge. Rate of resorption and antigenicity could be controlled by graded crosslinking of collagenous framework. Four basic examples of clinical use of collagen sponge are presented: as wound (burn) dressing material, as a matrix for bone and cartilage repair, as an intravaginal contraceptive diaphragm, and as surgical tampons.
Blood‐compatible materials by fluid perfusion
Authors: Predecki Paul , Russell P. A. , Newman M. M. 
Published: December 2004

AbstractThe feasibility of preventing platelet adhesion to porous foreign surfaces in contact with blood by passing (perfusing) a physiologic fluid through the pores into the blood was tested. Porous‐walled tubes of Teflon (Gore‐tex) and aluminosilicate ceramic were perfused with lactated Ringer's solution at rates between 3.13 and 0.3 cc/min per cm2 of perfused surface and exposed to heparinized and unheparinized flowing human whole blood for periods of 3–6 min. Under these conditions, with 0.159 cm I.D. tubes and a mean blood flow rate of 8.3 cm/sec, the adhesion of all blood cells was prevented, compared with the adhesion of 1 to 8 × 106 platelets/cm2 on the nonperfused controls. The adhesion of plasma proteins was also markedly reduced as determined by bromophenol blue staining.The critical perfusion rate to prevent platelet adhesion to Gore‐tex (0.5 μ pore size, 60% pore volume) was found to be between 0.04 and 0.3 cc/ (min · cm2). The boundary layer produced by a perfused segment of porous tubing prevented platelet adhesion for several centimeters downstream from the perfusing segment under experimental conditions used.
Thromboresistance of graft‐type copolymers with hydrophilic–hydrophobic microphase‐separated structure
Authors: Nakashima Toshihide , Takakura Koichi , Komoto Yoshiaki 
Published: December 2004

AbstractGraft‐type copolymers composed of hydrophilic poly (hydroxyethyl methacrylate) (PHEMA) as a backbone and a small amount of hydrophobic poly (methylmethacrylate) (PMMA) as a long branch exhibit excellent thromboresistance.The interrelationship between the thromboresistance and microstructure of the graft‐type copolymers as well as the water structure in the hydrated polymers has been investigated. It was concluded that both the structure of hydrophobic domain dispersed in the hydrophilic matrix and the water bound to the polymer may be responsible for the excellent thromboresistance of the graft‐type copolymers.
Compliance as a factor effecting the patency of a copolyurethane vascular graft
Authors: Lyman D. J. , Fazzio F. J. , Voorhees H. , Robinson G. , Albo D. 
Published: December 2004

AbstractA new solid‐wall vascular graft which has a compliance approximating that of the natural artery has been prepared from a copolyether–urethane material. Six of nine of these compliant grafts implanted in dogs were patent on removal, the longest implant time being 77 days for a 4‐mm I.D. femoral artery graft. This is in contrast to noncompliant grafts of the same copolyurethane in which failure usually occurred within 48 hr.
Microporous glassy fillers for dental composites
Authors: Mabie C. P. , Menis D. L. 
Published: December 2004

AbstractA microporous filler giving greatly improved finishability, systemic nontoxic X‐ray opacification, low thermal expansion (27.2 × 10−6/°C), and satisfactory translucencies has been developed for dental composite resin restorations. These fillers are prepared from frits obtained by the low‐temperature calcination of gelled inorganic sols followed by a pulsed high‐temperature treatment. Composites prepared from these fillers are within the range of commercial products with regard to strength and setting contraction.
Transport properties of hydrolyzed polyacrylonitrile
Authors: Dabrovská L. , Praus R. , Stoy V. , Vacik J. 
Published: December 2004

AbstractMeasurements of the permeability coefficients of various compounds up to a molecular weight of about 70,000 have shown clearly that membranes prepared from hydrolyzed polyacrylonitrile are about 10 times more permeable than those made of poly(2‐hydroxyethyl) methacrylate. The higher permeability is probably due more to the higher water content (about 75%) than to the type of network. The high mechanical strength of the membranes and their good permeability to compounds possessing a comparatively high molecular weight seem to designate the material for some new applications in medicine.
A novel technique for studying the adsorption of plasma proteins on hydrophobic surfaces
Authors: Bagnall R. D. , Annis J. A. D. , Arundel P. A. 
Published: December 2004

AbstractA method is shown for deducing the surface area of a pendant drop from the same profile photograph as is normally used to determine interfacial tension. Manipulation of such drops by a micrometer syringe then enables the pendant drop to be used as a surface balance for studying adsorption from bulk solutions. Results are given for the compression of films from solutions of albumin, γ‐globulin, fibrinogen, albumin–γ‐globulin mixture and albumin–γ‐globulin–fibrinogen mixture, and from serum, plasma, and blood at the isooctane–buffer interface. It is suggested that γ‐globulin and fibrinogen films are unfolded at the interface but that albumin films are different in that they consist of an inner, unfolded layer and an outer, globular layer. A film from serum resembles that from γ‐globulin alone, and not that from albumin–γ‐globulin mixture, whereas a film from plasma resembles that of fibrinogen at low compression and that of albumin–γ‐globulin–fibrinogen mixture at high compression. A film from blood is shown to resemble that from plasma.
Tissue response to allergenic leachables from dental materials
Authors: Kallus T. , Hensten‐Pettersen A. , Mjör I. A. 
Published: December 2004

AbstractIn addition to toxic reactions to dental materials, some individuals may develop or exhibit hypersensitivity reactions to leachable components. An experimental model combining the guinea pig maximization test for induction of hypersensitivity and the subcutaneous implantation of dental cements is described. Guinea pigs immunized with AH 26, an epoxy‐bisphenol resin, showed an increased tissue response to AH26 implants. Guinea pigs immunized with zinc oxide–eugenol did not show a similarly increased response, possibly because of an anti‐inflammatory effect of eugenol. The experimental model may prove useful in predicting the effect of leachable allergens from dental materials in sensitized individuals.
The glutaraldehyde‐stabilized porcine aortic valve xenograft. II. Effect of fixation with or without pressure on the tensile viscoelastic properties of the leaflet material
Authors: Lee J. Michael , Boughner Derek R. , Courtman David W. 
Published: December 2004

AbstractWe have examined the tensile viscoelastic properties of circumferential and radial strips of porcine aortic valve leaflets following fixation in glutaraldehyde and formaldehyde, with or without pressure. After aldehyde treatment, the radial strips remained weaker and less stiff than circumferential strips and responded slightly differently to the treatment. After fixation, with or without pressure, the radial strips showed large changes in stress‐strain and hysteresis responses due to initial loading, and there was a twofold reduction in tensile strength and final stiffness. For strips in both directions, fixation without pressure produced doubled extensibility and a ramping stress‐strain curve. Permanent (plastic) deformation of 5–20% occurred as a result of cyclic loading, stress relaxation, and creep experiments. Pressure fixation, however, produced little change in stress‐strain results other than a simple shift to lower strain and produced no plasticity. Both methods of fixation reduced stress relaxation and creep. Mechanical test results are consistent with a loss of ground substance matrix during fixation. Reductions in tensile strength after fixation may be due to “riveting” of collagen geometry, producing local stress concentrations.
Isolation of serum protein organometallic corrosion products from 316LSS and HS‐21 in vitro and in vivo
Authors: Woodman J. L. , Black J. , Jiminez S. A. 
Published: December 2004

AbstractAn investigation into blood‐borne organometallic compounds that arise from the corrosion of metals used in orthopedic prosthetic devices was conducted using an in vivo rat model with an implantation time of 10 days and an in vitro human serum model with an incubation time of 5 days. Both models involved 316LSS and HS‐21Haynes Stellite 21: Stellite Division of Cobalt Corporation, Kokomo, Indiana (An alloy of very similar composition to ASTM F‐75)
in the spherical powder form of 55 ± 5 μm microns in diameter at three different surface areas to body weight ratios. Gel chromatography on cross‐linked dextran (G‐200) was used to fractionate the serum proteins which bound the metal ions (chromium, cobalt, and nickel) released and identify them. Atomic‐absorption‐spectrophotometry analysis measured the concentration of the metal ions in each serum protein peak as well as whole serum from both models, and red cell and tissue from the in vivo model. Within the serum proteins, the metal ions were bound to two of the principal serum protein peaks. Similar distributions of the metals among the serum protein peaks were not noted.
Component wear of total knee prostheses using Ti‐6Al‐4V, titanium nitride coated Ti‐6Al‐4V, and cobalt‐chromium‐molybdenum femoral components
Authors: Peterson C. D. , Hillberry B. M. , Heck D. A. 
Published: December 2004

AbstractA knee simulator was used to study the wear of carbon fiber reinforced UHMWPE(Poly Two) (Poly Two is a registered trademark of Zimmer, USA) tibial and patellar components against Ti‐6Al‐4V, titanium nitride (TiN)‐coated Ti‐6Al‐4V, and cobaltchromium‐molybdenum femoral components. The prostheses tested were regular sized Miller‐Galante total knees mounted on 316L stainless steel fixtures using bone cement. An environmental chamber surrounded the knee and maintained bovine serum lubricant at 37°C. The specimens were tested using consecutive blocks of 464 level walking steps, 8 ascending stairs and 8 descending stairs for a total of 100,000 steps. The wear mechanisms found on the tibial components were scratching, carbon fiber associated damage, surface deformation, pitting, minor abrasion, and delamination. Three forms of carbon fiber associated damage were identified; fibers pulled from the surface, broken fibers, and UHMWPE removed from the surface fibers. The SEM evaluation revealed a pit forming mechanism. No correlation was found between femoral component material and tibial surface damage. Visual examination of the femoral components revealed no signs of wear or scratching on the cobalt‐chromium‐molybdenum or TiN‐coated Ti‐6Al‐4V components. There were, however, many light surface scratches on the uncoated Ti‐6Al‐4V components, which were also observed in a supplementary test of an uncoated Ti‐6Al‐4V component tested with a conventional polyethylene tibial component.
Hydrogels for buccal drug delivery: Properties relevant for muco‐adhesion
Authors: de Vries M. E. , Boddé H. E. , Busscher H. J. , Junginger H. E. 
Published: December 2004

AbstractIn order to develop a muco‐adhesive hydrogel for buccal drug delivery it is necessary to understand fully the properties determining adhesiveness as well as mechanisms involved. In this study we measured glass transition temperatures, water contact angles and the peel‐ and shear detachment forces from porcine oral mucosa, of acrylic acid and butyl acrylate copolymers. The contact angle maximizes at 50% butyl acrylate content. The glass transition temperature decreases from 0% to 100% butyl acrylate. There seems to exist a certain combination of contact angle and glass transition temperature which is related to adhesiveness. This strongly suggests that, in order to obtain a muco‐adhesive hydrogel, at least two properties have to be optimized: (1) the polarity of the polymer surface and (2) the molecular mobility of the polymer groups.