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Amagata T Amagata A Tenney K Valeriote FA Lobkovsky E Clardy J Crews P 《Organic letters》2003,5(23):4393-4396
[structure: see text] Structurally unique steroids, isocyclocitrinol A (1) and 22-acetylisocyclocitrinol A (2), were isolated from the extract of a saltwater culture of sponge-derived Penicilliun citrinum. The structures were established by analysis of 1D and 2D NMR data. The absolute structures were determined on the basis of X-ray structure analysis and application of modified Mosher's method. Furthermore, the structure of cyclocitrinol (3a) previously isolated from a terrestrial P. citrinum was revised as 3b. Compounds 1 and 2 showed weak antibacterial activity against Staphylococcus epidermidis and Enterococcus durans. 相似文献
133.
Transition metal complexes coordinated by an NAD(P)H model compound and their enhanced hydride-donating abilities in the presence of a base 总被引:1,自引:0,他引:1
Kobayashi A Konno H Sakamoto K Sekine A Ohashi Y Iida M Ishitani O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(14):4219-4226
The ruthenium(II) and rhenium(I) complexes containing an NAD(P)H model compound, 1-benzyl-1,4-dihydronicotinamide (BNAH), as ligand, [Ru(tpy)(bpy)(BNAH)]2+ (1 a) and [Re(bpy)(CO)3(BNAH)]+ (1 b), were quantitatively produced by the reaction of the corresponding metal hydrido complexes with BNA(+) (1-benzylnicotinamidium cation). In the presence of base with pK(a) = 8.9, 1 a and 1 b have much greater reducing power than "free" BNAH. The oxidation potentials of 1 a in the absence and the presence of triethylamine were 0.55 V and -0.04 V, respectively, versus Ag/AgNO(3), whereas that of "free" BNAH was 0.30 V. Spectroscopic results clearly showed that the base extracts a proton from the carbamoyl group on 1 a and 1 b to give the deprotonated BNAH coordinating to the transition-metal complexes [Ru(tpy)(bpy)(BNAH-H+)]+ (3 a) and [Re(bpy)(CO)3(BNAH-H+)] (3 b); this deprotonation underlies the enhancement in reducing ability. The deprotonated forms 3 a and 3 b can efficiently reduce other NAD(P) models to give the corresponding 1,4-dihydro form, resulting in the deprotonated BNA+ being coordinated to the metal complexes [Ru(tpy)(bpy)(BNA(+)-H+)]2+ (2 a) and [Re(bpy)(CO)3(BNA+-H+)]+ (2 b); "free" BNAH and the protonated adducts 1 a and 1 b cannot act in this way. X-ray crystallography was performed on the PF6- salt of 2 a, and showed that the deprotonated nitrogen atom on the carbamoyl group coordinates to the ruthenium(II) metal center with a bond length of 2.086(3) Angstroms. Infrared spectral data suggested that the deprotonated carbamoyl group on the reduced forms 3 a and 3 b is converted to the imido group, and that the oxygen atom coordinates to the metal center. 相似文献
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Dr. Akiko Nakamura Dr. Marwa Abdel Latif Prof. Paul A. Deck Prof. Neal Castagnoli Jr. Prof. James M. Tanko 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):823-829
Mechanistic studies with 5-ethyl-3-methyllumiflavinium (Fl+) perchlorate, a biomimetic model for flavoenzyme monoamine oxidase B (MAO-B) catalysis, and the tertiary, allyl amine 1-methyl-4-(1-methyl-1 H-pyrrol-2-yl)-1,2,3,6-tetrahydropyridine (MMTP) reveal that proton-coupled electron transfer (PCET) may be an important pathway for MAO catalysis. The first step involves a single-electron transfer (SET) leading to the free radicals Fl. and MMTP., the latter produced by deprotonation of the initially formed and highly acidic MMTP.+. Molecular oxygen (O2) is found to play a hitherto unrecognized role in the early steps of the oxidation. MMTP and several structurally similar tertiary amines are the only tertiary amines oxidized by MAO, and their structural/electronic properties provide the key to understanding this behavior. A general hypothesis about the role of SET in MAO catalysis, and the recognition that PCET occurs with appropriately substituted substrates is presented. 相似文献
137.
Akiko Sekine Hidehiro Uekusa Yuji Ohashi Kimihiro Yoshimura Mikio Yagi Jiro Higuchi 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(12):1462-1464
The crystal structures of 4-nitro-9,10-dihydrophenanthrene, C14H11NO2, (I), and 4-nitrophenanthrene, C14H9NO2, (II), the latter having two crystallographically independent molecules, show that the molecules are not planar. The dihedral angles between the phenyl rings of the biphenyl skeletons are 28.64 (8)° for (I), and 10.34 (15) and 11.75 (13)° for the two molecules of (II). The differences in the dihedral angles have an effect on the photochemical reactivity of the molecules. 相似文献
138.
Akiko Hashimoto Takeji Takamura‐Enya Yoshimitsu Oda 《Photochemistry and photobiology》2019,95(6):1403-1411
Photodynamic therapy (PDT) is a widely used medicinal treatment for the cancer therapy that utilizes the combination of a photosensitizer (PS) and light irradiation. In this study, we synthesized two novel C60 fullerene derivatives, compounds 1 and 2 , with a psoralen moiety that can covalently bind to DNA molecules via cross‐linking to pyrimidine under photoirradiation. Along with several fullerene derivatives, the biological properties of several novel compounds have been evaluated. Compounds 1 and 2 , which have been shown to induce the production of hydroxyl radicals using several ROS detecting reagents, induced DNA strand breaks with relatively weak activities in the in vitro detection system using a supercoiled plasmid. However, the psoralen‐bound fullerene with carboxyl groups ( 2 ) only showed genotoxicity in the genotoxicity assay system of the umu test. Compound 2 was also seen to have cytotoxic activities in several cancer cell lines at higher doses compared to water‐soluble fullerenes. 相似文献
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