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Biomedical subjects

J Gallucci

Publications and source records attributed to J Gallucci.

At least 19 recordsLinked to original sources
PubMed2001

Structural, magnetic and catalytic properties of a self-recognized mu-oxo-bridged diiron(III) bis(benzimidazole) complex.

The inherent nonplanarity and C(2) symmetry of the dimethyl-substituted bis(benzimidazole) ligand (Me(2)BBZ) results in two distinct atropisomers that, when separated, have been suggested to have potential for chiral recognition and catalysis. Here is reported the synthesis and characterization of a diiron mu-oxo-bridged bis(benzimidazole) complex, 1, that provides indirect support for this hypothesis. Dimerization of a racemic solution of iron-Me(2)BBZ monomers via the mu-oxo bridge yields (+,+) and (-,-) diastereomers whose complementary association can be attributed to the inherent sidedness of the metal-Me(2)BBZ interaction surface, and to the differences in the torsional angles of the phenyl(benzimidazole) units (34 degrees) and the Schiff base linkages (54 degrees). These results highlight the steric differences between the phenyl(benzimidazole) and Schiff-base portions of the ligand, features that could be important in the chiral recognition of ligands and in differentiating substrate trajectories as required for asymmetric catalysis. For completeness, studies of 1 in the catalytic epoxidation of styrene are also reported.

Journal Article↗
PubMed2000

Synthesis and characterization of the dimethyl-substituted bisbenzimidazole ligand and its manganese complex.

Macrocycles with unique properties provide new avenues for the design of novel catalysts and materials. Here, we report, for the first time, the synthesis and characterization of the dimethyl-substituted bisbenzimidazole ligand (Me2BBZ) and its manganese complex (Mn-Me2BBZ). The Me2BBZ ligand is similar to porphyrin and phthalocyanine macrocycles in terms of its cavity size and metal-binding mode, but owing to electronic and charge differences, it exhibits properties that make it distinct from its structural counterparts. For instance, the optical spectra of bisbenzimidazoles lack transitions in the 500-900 nm region. Perhaps the most significant feature of the Me2BBZ ligand, however, is its inherent nonplanarity. Geometric restraints within this nonplanar ligand give rise to two atropisomers, which, when separated, could have potential in chiral catalysis and recognition. In addition, here we show that this nonplanarity can help to promote unusual crystal-packing interactions. Within the structure of the Mn-Me2BBZ complex, intermolecular pi-stacking interactions of the phenyl and benzimidazole groups lead to the formation of a distinct two-dimensional "staircase" lattice comprised of alternating Mn-Me2BBZ atropisomers. The potential significance of this structural arrangement is revealed by temperature-dependent magnetic studies that indicate weak antiferromagnetic coupling between the metal ions in the crystal. Fine-tuning of these long-range electronic and magnetic interactions could be useful for the design of novel molecular materials.

Journal Article↗
PubMed2000

Structural trends in first-row transition-metal bis(benzimidazole) complexes.

Dimethyl-substituted bis(benzimidazole) (Me2BBZ) is a novel macrocyclic ligand that possesses an intrinsic nonplanarity. To examine how metal-ion binding affects the magnitude of this nonplanarity, we have determined the structures of a periodic series of Me2BBZ complexes bound to Mn(II), Fe(II), Co(II), Ni(II), and Cu(II). These studies demonstrate that the extent of ligand ruffling and metal doming is indeed influenced by the nature of the metal. Concomitant with the periodic decrease of the ionic radii of the encapsulated divalent metal ion, a decrease in the magnitude of both the ligand nonplanarity and the metal out-of-the-plane distance is observed. For the metal out-of-the-plane distance, this correlation persists until the metal finally moves into the mean ligand plane. For the nonplanar distortion, the extent of the nonplanarity decreases to a limiting value that is intrinsic to the Me2BBZ ligand due to steric factors. These observations indicate that the relative sizes of the metal ion and the Me2BBZ ligand cavity have profound effects on the structural features of the metal-ligand complex.

Journal Article↗
PubMed1996

The cardiopulmonary, eicosanoid, and tissue microanatomic effects of fluconazole during graded bacteremia.

Imidazole compounds have been shown to be beneficial in systemic sepsis and inflammation. The purpose of this study was to delineate the effects of fluconazole on systemic hemodynamics and on microanatomy of the heart, lung, liver, and kidney parenchyma of swine during graded bacteremia. Eighteen adult swine were studied in three groups: 1), anesthesia control; 2), septic control (Aeromonas hydrophila, 10(9)/mL, infused i.v. for 4 h); 3) fluconazole (fluconazole, 30 mg/kg i.v., followed by A. hydrophila infusion). After 4 h of graded bacteremia, autopsy was performed. Compared with the septic control group, cardiac index, oxygen delivery, and oxygen consumption were reduced significantly after fluconazole pretreatment, and mixed venous hemoglobin oxygen saturation (SVO2) and oxygen extraction were increased. Plasma thromboxane A2 and leukotriene levels were not affected by fluconazole. Computerized digital image analysis of the liver, heart, and kidney specimens revealed no statistically significant differences between the septic control group and fluconazole-pretreated animals. In the lung specimens, preinfusion of fluconazole decreased alveolar wall thickness in septic swine (anesthesia control group: 8.15 x 10(-3) +/- 1.3 x 10(-3)mm versus septic control group: 9.9 x 10(-3) +/- 1.3 x 10(-4) versus fluconazole group: 6.8 x 10(-3) +/- 1.6 x 10(-3); p < or = .05). Fluconazole pretreatment before graded bacteremia has no beneficial effect on cardiopulmonary performance or septic tissue edema of the heart, kidney, or liver. Tissue oxygen metabolism might be down-regulated by fluconazole. However, preinfusion of fluconazole appears to normalize the sepsis-induced increase in pulmonary alveolar wall thickness. The net significance of these changes on clinical outcome is not clear from these data.

Anesthesia↗
PubMed1992

Structure of (E)-5-(methoxymethylene)-2,4-imidazolidinedione.

C5H6N2O3, Mr = 142.11, monoclinic, P2(1)/n, a = 3.862 (1), b = 16.329 (2), c = 10.088 (1) A, beta = 98.77 (2) degrees, V = 628.7 (2) A3, Z = 4, Dx = 1.50 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 1.18 cm-1, F(000) = 296, T = 296 K, R = 0.035 for 1124 independent reflections with I greater than 3 sigma(I). The structure is a hydantoin derivative with a methoxymethylene group substituted at the 5-position. Excluding the H atoms, the molecule is planar to within 0.032 A. All of the N and O atoms are involved in an intermolecular hydrogen-bonding network via N--H...O and C--H...O interactions. The packing arrangement is a linear ribbon motif with the ribbons stacked to form the short a axis.

Chemical Phenomena↗
PubMed1987

Stereocontrolled syntheses for the six diastereomeric 1,2-dihydroxy-4,5-diaminocyclohexanes: PtII complexes and P-388 antitumor properties.

Stereocontrolled syntheses for the six diastereomeric 1,2-dihydroxy-4,5-diaminocyclohexanes 3a-f from cyclohexene diamines cis-4 and trans-5 are described. Cbz-protected species cis-9 and trans-11, respectively, served as a source of stable Cbz-protected precursors to these cyclohexanediol diamines (CDD), which were liberated upon catalytic (H2, Pd/C) hydrogenation. Catalytic osmylation of 9 afforded a mixture of diastereomeric diols 13 and 14, which served as precursors to cis-anti-cis CDD 3b and cis-syn-cis CDD 3a, respectively, whereas osmylation of 11 yielded the expected single product 12, the precursor to cis-anti-trans CDD 3d. Epoxidation of olefins 9 and 11 afforded oxiranes 15 and 17, respectively, which upon acid-catalyzed hydrolysis produced the corresponding Cbz-protected diols 16 and 18, which served as precursors to CDD trans-anti-cis 3c, and trans-anti-trans 3e. Formation of diol 18 from oxirane 17 was accompanied by formation of 2-oxa-4-azabicyclo[3.3.1]nonan-3-one 19. CDD trans-syn-trans 3f was prepared from diol 12 via regioselective monoacetylation, yielding 22, followed by oxidation to afford ketone 24. Sodium borohydride reduction and acetylation produced diacetate precursor 26. PtIICl2 complexes of five of the diamines (3a-d,f) are described, and their activities were compared with cisplatin (1) by employing P-388 leukemia implanted CDF1 mice. The data indicate that stereochemistry of the amino groups on the cyclohexanediamine ligand modulate the expression of toxic effects, and depending upon hydroxyl and amino group stereochemistry, there is a marked effect on complex formation (e.g., Cl2PtII-3e) and solubility characteristics (e.g., Cl2PtII-3c). Acetylation of the hydroxyl functions in selected isomers (28a-c) rendered the PtII complexes inactive. A single-crystal X-ray structure of compound 3a was determined at room temperature and indicated the cis-syn-cis arrangement of the OH and NH2 groups.

Animals↗