bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses and Magnetic Properties of 1,4,8,11-Tetraazacyclotetradecanenickel(II) Tetra-, Hexa-, and Octa-cyanometalates
Authors: Nowicka Beata , Hagiwara Masayuki , Wakatsuki Yasuo , Kisch Horst 
Published: December 2003

Abstract
A series of 1,4,8,11-tetraazacyclotetradecanenickel(II) cyanometalates ([Ni(cyclam)]3[Fe(CN)6]2·11H2O (1), [Ni(cyclam)]2[Mo(CN)8]·3H2O (2), [Ni(cyclam)]2[W(CN)8]·3H2O (3), and [Ni(cyclam)][Pt(CN)4]·3H2O (4) (cyclam = 1,4,8,11-tetraazacyclotetradecane)) was obtained and characterised. Magnetic-susceptibility measurements showed a high-spin configuration (S = 1) of Ni(II) in all compounds, which was attributed to the interaction of cyano ligands with free axial coordination sites on nickel. The presence of bridging cyano groups in 1 was confirmed by IR and visible reflectance spectra. Compound 1 shows a long-range magnetic order below 8 K.
Catalytic Esterification of Alcohols, Carboxylic Acids and Transesterification Reactions with Cerium(IV) Triflate
Authors: Iranpoor Nasser , Shekarriz Marzieh 
Published: December 2003

Abstract
Esterification reactions of alcohols with acetic, chloroacetic, trifluoroacetic, propionic, stearic, and benzoic acids were catalyzed with Ce(OTf)4 in a solvent or under solvent-free conditions with high yields. The formylation and acetylation of primary and secondary alcohols were also easily achieved in ethyl formate and ethyl acetate. A high retention of the configuration was observed in the acetylation and formylation of (−)-menthol.
Synthesis of Unsymmetrically Substituted Antimony(V) Tetraphenylporphyrins
Authors: Satoh Wataru , Masumoto Shuji , Shimizu Masakazu , Yamamoto Yohsuke , Akiba Kin-ya 
Published: December 2003

Abstract
The following nine unsymmetrically axially substituted antimony(V) tetraphenylporphyrins with an antimony–carbon bond or an antimony–fluorine bond were synthesized: [(TPP)Sb(Me)(OEt)]+ClO4− (1-ClO4), [(TPP)Sb(Me)(OC6H4CH3-p)]+ClO4− (2-ClO4), [(TPP)Sb(Me)(SC6H4CH3-p)]+ClO4− (3-ClO4), [(TPP)Sb(Me)(NHC6H4CH3-p)]+ClO4− (4-ClO4), [(TPP)Sb(Me)(NHCH2C6H5)]+ClO4− (5-ClO4), [(TPP)Sb(Me)(OC(=O)C6H4Cl-m)]+PF6− (6-PF6), [(TPP)Sb(Me)(Et)]+PF6− (7-PF6), [(TPP)Sb(Me)(CH2CHMe2)]+PF6− (8-PF6), and [(TPP)Sb(F)(OH)]+ClO4− (9-ClO4). All nine compounds were stable towards atmospheric moisture. X-Ray crystallographic analysis of 6-PF6 revealed that the antimony atom lies at 0.182 Å out-of-plane of the four nitrogens (Δ4N) toward the carbon atom; 6-PF6: space group P21/n, a = 25.49(2), b = 11.27(1), c = 16.58(1) Å, β = 96.74(5)°, R = 0.064.
Reaction of N1,N2-Diarylacetamidines with Ethyl 2-Oxoindolin-3-ylidenecyanoacetate and Benzylidenemalononitriles
Authors: Gomaa Mohsen A-M , El-Din Ahmed M Nour , Mohamed Azza A 
Published: December 2003

Abstract
1′-Aryl-6′-arylimino-2,2′-dioxospiro[(2,3-dihydro-1H-indole)-3,4′-perhydropyridine]-3′-carbonitriles 5a—d together with ethyl 2-amino-4-[1-aryl-2,6-bis(arylamino)-4-hydroxy-1,4-dihydro-4-pyridyl]quinoline-3-carboxylate 9a—c were obtained from the reaction of N1,N2-diarylacetamidines 1a—d with ethyl 2-oxoindoline-3-ylidenecyanoacetate 3. Acetamidines 1a—c also reacted with the benzylidenemalononitriles 10a—d to afford the adducts 1,4,5,6-tetrahydropyridines 13a—f.
Kinetic and Mechanistic Investigation of a Hydrolytic Catalytic Antibody Having Remarkable Substrate Specificity: Substituent Effects on Catalysis
Authors: Wada Yumiko , Yamamoto Masayoshi , Sudo Yukio , Ono Mitsunori 
Published: December 2003

Abstract
Monoclonal antibodies were raised against p-nitrophenyl phosphonate to elicit catalytic antibodies capable of hydrolyzing p-nitrophenyl carbonates. Of 34 clones selected, three clones catalyzed the hydrolysis of methyl p-nitrophenyl carbonate. Interestingly, 4A1, an antibody out of those clones, showed a significant rate acceleration against substrates that differ from the given haptenic structure in the carrier-proximal region. The rate acceleration (kcat/kuncat) for one of the specific substrates is 6.4 × 104, 20-fold higher than that of a substrate congruent with the hapten. Kinetic analysis of Km and kcat values, as well as the affinity constant (Kd) values of the corresponding transition-state analogs, indicated that the rate enhancement is associated with a decrease in the activation energy due to stabilization of the transition-state in the cleavage reaction. In addition, the inactivation of 4A1 catalytic antibody upon hydrolysis of a particular substrate was observed. The 600 MHz 13C NMR measurement clearly showed that the 13C-labeled fragment attached covalently to the 4A1 antibody, proving formation of an acyl-antibody. Further kinetic analysis study demonstrated that the 4A1 catalytic antibody uses a multistep kinetic sequence for the hydrolytic reaction.
Organic Photoelectrochemical Cell Mimicking Photoinduced Multistep Electron Transfer in Photosynthesis: Interfacial Structure and Photoelectrochemical Properties of Self-Assembled Monolayers of Porphyrin-Linked Fullerenes on Gold Electrodes
Authors: Imahori Hiroshi , Ozawa Shinichiro , Ushida Kiminori , Takahashi Masao , Azuma Takayuki , Ajavakom Anawat , Akiyama Tsuyoshi , Hasegawa Masato , Taniguchi Seiji , Okada Tadashi , Sakata Yoshiteru 
Published: December 2003

Abstract
Self-assembled monolayers (SAMs) technique has been applied to porphyrin-linked fullerene systems to mimic supramolecular photoinduced charge-separation (CS) events in photosynthesis. Porphyrin-linked C60 molecules with a sulfide group were designed to self-assemble on a gold surface using S–Au interaction. The structure of the SAMs formed on gold electrodes was investigated by spectroscopic methods including X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)-visible spectroscopic ellipsometry, UV-visible absorption spectroscopy, and Fourier transform infrared (FTIR) spectroscopy as well as electrochemical studies. These results indicate that the SAMs have loosely packed structure; the porphyrin-C60 molecules are tilted and nearly parallel onto the gold surface. Short-circuit photocurrent with a level of sub-μA cm−2 was observed for the photoelectrochemical cell in the presence of methylviologen (MV) under illumination with ca. 4 mW cm−2. The maximum intensity of the photocurrent in free-base porphyrin-C60 system is five times larger than that in the corresponding free-base porphyrin system, indicating that C60 is an effective mediator in multistep electron transfer (ET) processes. A possible mechanism for the photocurrent generation is discussed in terms of the photodynamics of porphyrin-linked fullerenes in solution.
Donor–Acceptor Binary Photocatalysis System Illustrated by the Intramolecular Cyclization of a Cyclopropanone Acetal Tethered to Cyclohexen-2-one
Authors: Oku Akira , Miki Toshiyuki , Abe Manabu , Ohira Masatoshi , Kamada Tohru 
Published: December 2003

Abstract
Irradiation of 2-[3-(2-methoxy-1-phenyl-2-TBDMSO-cyclopropyl)-propyl]-2-cyclohexen-1-one (5) in the presence of Mg(ClO4)2 (1 mol equiv) and 9,10-dicyanoanthracene (DCA, 0.5 mol equiv) in acetonitrile formed methyl 5-oxo-1-phenyldecahydro-1-naphthaleneacetate (6) in 63% yield. When pyrene was adopted in place of DCA, the yield of 6 was 38%. The results indicate that the photocyclization of 5 induced by the SET can be catalyzed by both donor- and acceptor-type photocatalysts. Irradiation of a similar substrate, 4-(2-methoxy-1-phenyl-2-TBDMSO-cyclopropyl)butyl 2-naphthyl ketone (21), produced methyl 2-hydroxy-2-(2-naphthyl)-1-phenylcyclohexaneacetate (27) in 13% in the presense of p-dicyanobenzene (0.1 mol equiv) and 8% in its absence.
Allenyl(vinyl)methane Photochemistry. Photochemistry of Methyl 4,4-Dimethyl-2,5,6-heptatrienoate Derivatives
Authors: Tsuno Takashi , Sugiyama Kunio 
Published: December 2003

Abstract
Both the direct and sensitized photolyses of [2-(1,2-propadienyl)-substituted alkylidene]malonates gave mainly intramolecular [2+2] cycloadducts. On the other hand, the direct irradiation of methyl (E)-4,4-dimethyl-2,5,6-heptatrienoate (3a) competitively underwent E–Z geometric isomerization and intramolecular [2+2] cycloaddition, though prolonged irradiation led to [2+2] cycloadducts as main products. For methyl (E)-4,4,7-trimethyl-2,5,6-octatrienoate (3b), the intramolecular [2+2] cycloaddition occurred under both direct and sensitized irradiation and the E–Z geometric isomerization scarcely occurred. In these allenyl(vinyl)methanes under direct irradiation, the 1,2-propadienyl-substituted esters gave a 1,2-propadienylcyclopropane or (2-ethenylidenecyclopropyl)acetate as a minor product. When 3b was irradiated in the presence of hydrogen selenide in toluene, cyclopentenes were formed. The formation of the cyclopentenes indicated that the biradical intermediate is a cyclopentane-1,3-diyl radical. By MO calculations of the model compounds for the chromophores of the esters, it is suggested that the preferential initial bond for the 1,2-butadienyl- or 3-methyl-1,2-butadienyl-substituted esters is between the C6 (allene center carbon) and C2 (α-carbon), while 1,2-propadienyl-substituted esters can also be bonded between the C5 and C3 (β-carbon).
Preparation of Acyl(carboxylato)bis(tertiary phosphine)palladium(II) Complexes by C–O Bond Cleavage of Carboxylic Anhydrides on Interaction with Palladium(0) Complexes. Catalytic Hydrogenation of Carboxylic Anhydrides to Aldehydes by Palladium Complexes
Authors: Nagayama Kazuhiro , Kawataka Futoshi , Sakamoto Masato , Shimizu Isao , Yamamoto Akio 
Published: December 2003

Abstract
Acyclic anhydrides oxidatively added to [Pd(styrene)(PMeR2)2] (R = Me, 2a; Ph, 2b) under mild conditions with C–O bond cleavage to give the corresponding trans-acyl(carboxylato)palladium complexes 3a—3h. Cyclic acid anhydrides also added to 2a to yield trans-acyl(carboxylato)palladium complexes 4a—4c, while reaction of 2a with phthalic anhydride afforded the palladalactone 4d generated via oxidative addition followed by decarbonylation. The acetyl(acetato)palladium complex 3a reacted with dihydrogen or formic acid to give acetaldehyde and acetic acid. Catalytic hydrogenation of acyclic anhydrides by a palladium complex was achieved to form the corresponding aldehydes and carboxylic acids.
Study on a New Iron Phosphate Crystalline Phase
Authors: Ai Mamoru , Ohdan Kyoji 
Published: December 2003

Abstract
An iron phosphate having a new crystalline phase was obtained by a partial reduction of iron(III) orthophosphate with a reducing agent, usually oxalic acid, in the presence of oxygen and a large amount of water vapor at a low temperature of 200 to 250 °C. XRD spectra of the new phase (designated as M-phase) are similar to those of clay minerals. The effects of reaction variables, such as reducing agent, reaction period, starting iron phosphate, temperature, and oxygen feed rate, on the formation of M-phase were studied. Some characterizations of this M-phase were also attempted.
π-Conjugated Polymers Bearing Electronic and Optical Functionalities. Preparation by Organometallic Polycondensations, Properties, and Their Applications
Authors: Yamamoto Takakazu 
Published: December 2003

Abstract
Various π-conjugated polymers have been obtained by using organometallic polycondensations mediated by organotransition metal complexes. For example, Ni(0) complex-promoted dehalogenation polycondensation of dihaloaromatic compounds X–Ar–X affords poly(arylene)s,n. Pd-catalyzed polycondensation gives poly(arylene–ethynylene)s,n. These polymers are electrochemically active, electrically conductive, and light-emitting. Their well-characterized linear structure brings about unique packing of the polymer molecules in the solid. In this paper, we describe preparation by the organometallic polycondensations, basic properties, the ordered structure in the solid, and applications for electronic and optical devices of π-conjugated polymers.rr–C≡C–Ar′–C≡C
Magnetic Properties of TTF-Type Charge Transfer Salts in the Mott Insulator Regime
Authors: Yoneyama Naoki , Miyazaki Akira , Enoki Toshiaki , Saito Gunzi 
Published: December 2003

Abstract
We have investigated the magnetic properties of several TTF-based Mott insulators consisting of dimerized/trimerized-donor units, which are classified into three subgroups: (1) β′-(BEDT-TTF)2X (X = ICl2, AuCl2) and (BEDT-TTF)2GaCl4 as strong dimer systems, (2) α′-(BEDT-TTF)2IBr2 salt as a weak dimer system, and (3) (BMDT-TTF)3ClO4(1,2-dichloroethane) and (BMDT-TTF)3AsF6(1,1,2-trichloroethane) as weak trimer systems. The group (1) compounds have localized spin systems with an S = 1/2 localized spin per dimer unit. In group (2), weak dimerization produces a fractional magnetic moment, which reflects the delocalization of the electrons, although the magnetism is described in terms of an S = 1/2 low-dimensional antiferromagnet. The ClO4 salt in the group (3) indicates the existence of a localized spin per trimer, whereas the trimerization is quite weak, because the inter-trimer Coulomb interactions generate the charge disproportionation resulting in the localization of electrons. The absence of the charge disproportionation brings about the feature of fractional magnetic moments in the AsF6 salts.
Cooperative Ligand Binding to Globular Protein(II). Binding of Dianionic Azo Dyes to Hen Egg White Lysozyme
Authors: Murakami Kiyofumi , Tsurufuji Katsuyoshi 
Published: December 2003

Abstract
The binding of five dianionic azo dyes: disodium 3-hydroxy-4-(2,4,5-trimethylphenylazo or 1-naphthylazo)-2,7-naphthalenedisulfonate, disodium 6-hydroxy-5-(4-sulfonatophenylazo or 4-sulfonato-1-naphthylazo)-2-naphthalenesulfonate, and disodium 2-(2-hydroxy-1-naphthylazo)-5-(4-sulfonatophenylazo)benzenesulfonate, to hen egg white lysozyme has been studied by an equilibrium dialysis method at pH = 7.0 (0.1 mol dm−3 phosphate buffer) and 25 °C. The measured binding isotherms showed that all of these dyes cooperatively bind to the protein, but the degree of the cooperativity differs from dye to dye. From the result that the maximum binding number (6) was about half of those for monoanionic dyes, these dye molecules were found to bind bifunctionally with their two sulfonato groups to the cationic residue pairs on the protein. The binding isotherms were analyzed on the basis of the stepwise binding scheme by a nonlinear regression analysis, and all the binding constants have been evaluated. The differences in the cooperative-binding behavior between dyes have been examined from the viewpoints of the structural difference between dyes and of the distribution of cationic residues on the protein. It was found that the hydrophobicity of each ligand plays a central role for the cooperativity, and that the orientation of the hydrophobic part of ligand in bound state as well as the distribution of charged residues on the protein also affect the binding behavior.
A Study of Electron Spin Polarization Transfer in a System of Photo-Excited Triplet Phthalocyanine and a Nitroxide Radical
Authors: Saiful Islam SM , Fujisawa Jun-ichi , Kobayashi Nagao , Ohba Yasunori , Yamauchi Seigo 
Published: December 2003

Abstract
Electron spin polarizations were studied for a system of excited triplet (T1) phthalocyanine (MTNPc; M = H2, Zn) and a nitroxide radical (TEMPO) in toluene solution by means of time-resolved EPR (TREPR) spectroscopy. TREPR spectra of the T1 state and the radical (R) were observed simultaneously. Spin polarizations of both signals were found to consist of two components with different decay rates. From analyses of the polarizations and the decay curves, it was found that the triplet polarizations are generated from anisotropic S1→T1 intersystem crossings and thermal populations. The initial and late polarizations on TEMPO were interpreted in terms of electron spin polarization transfer (ESPT) from T1 and a radical-triplet pair mechanism (RTPM) with a quartet precursor under J &lt; 0 (J; exchange coupling parameter), respectively. The ESPT rate was determined and found to be dependent on temperature and the central atom(s) of MTNPc. In the H2TNPc system, the ESPT rate is much slower than the diffusion rate and axial ligation of TEMPO remarkably accelerates the ESPT rate in the ZnTNPc system.
A Deuterium-Labeling Study on the Dehydrogenation of 2-Propanol with Ru–Pt/Carbon Catalyst in the Liquid-Film State Effective for the 2-Propanol/Acetone/Hydrogen Chemical Heat-Pump System
Authors: Meng Ning , Ando Yuji , Shinoda Sumio , Saito Yasukazu 
Published: December 2003

Abstract
A unique feature of the dehydrogenation of 2-propanol with Ru–Pt/carbon catalyst in the liquid-film state has been elucidated by means of various kinds of deuterium labeling. A quite large kinetic isotope effect for 2-propanol-d8 (kH/kD = 14.6) suggests that fission of the methine C–H bond in the isopropoxy intermediate is rate-determining in the overall process. The dominant formation of H2 for 2-propanol-O-d1 is explained in terms of rapid scrambling of deuterium together with a large kinetic isotope effect for fission of the methine C–D bond. This picture is supported by both the absence of an appreciable kinetic isotope effect for 2-propanol-O-d1 and the deuterium distribution among the liquid-phase components. The extent of hydrogen transfer from 2-propanol to acetone-d6 during the dehydrogenation reaction suggests suppression of the inhibitive adsorption of acetone, leading to a high catalytic activity in the region of high acetone concentration, which is essential for a 2-propanol/acetone/hydrogen chemical heat-pump system with high thermal efficiency.
Monomolecular Layer of the Alkylated Cytochrome b562 Formed at the Air/Water Interface
Authors: Kobayashi Kazutoshi , Nagamune Teruyuki , Furuno Taiji , Sasabe Hiroyuki 
Published: December 2003

Abstract
A method is provided for forming a monomolecular layer of cytochrome b562 at the air/water interface by introducing dialkyl chains onto a water-soluble cytochrome b562. The purpose of the present study was to form densely and/or regularly packed two-dimensional arrays of protein molecules. Protoheme, which is a prosthetic group of cytochrome b562, was extracted from cytochrome b562, and then dialkylated(dioctadecylated) with the synthetic-chemical procedure. This dioctadecylated heme was reconstituted with apo-cytochrome b562 in dimethyl sulfoxide–water mixtures in vitro. The reconstitution reaction was successful when the reaction time was greater than 50 min, the dimethyl sulfoxide content was 63% and the temperature was maintained at 10 °C. Surface pressure–area per molecule isotherm of the reconstituted dioctadecylated holo-cytochrome b562 was measured and this clearly shows the monolayer formation of the water-soluble protein on the water subphase. The coefficient of compressibility of the protein film was estimated and is discussed. It is found that reconstituted dioctadecylated holo-cytochrome b562 forms a stable and closely packed monomolecular layer on the water surface.
A Better Synthesis of Biruthenocene and Molecular Structures of [RuIICp(C5H4C5H4)CpRuIVNCC2H5](BF4)(B2F7)CH3NO2, [RuIICp(2,2′-bipyridine)(p-benzoquinone)]BF4 and Related Salts
Authors: Watanabe Masanobu , Sato Masaru , Nagasawa Akira , Kai Masahiro , Motoyama Izumi , Takayama Toshio 
Published: December 2003

Abstract
An interesting dimerization occurred during the oxidation of ruthenocene with an excess of p-benzoquinone containing BF3·Et2O (abbreviated p-Bq/BF3) in a mixed solution of benzene and hexane, which gave biruthenocenium(BF4)2 (A) in 89% yield. Reduction of A with TiCl3 gave biruthenocene in a good yield (68% from ruthenocene), which is the most elegant preparation of biruthenocene. Recrystallization of A from CH3NO2 containing C2H5CN gave a mixed-valence salt 3 formulated as [RuIICp(C5H4C5H4)CpRuIVC2H5CN](BF4)(B2F7)CH3NO2 in which C2H5CN coordinated to the RuIV center. The crystal of 3 was found to be monoclinic, space group P21/a, a = 9.8930(8), b = 15.445(3), c = 19.728(3)Å, β = 92.57(1)°, V = 3011.3(1) Å3, Z = 4, and the final R = 0.075and Rw = 0.093. Recrystallization of A from CH3NO2 containing 2,2′-bipyridine and p-benzoquinone gave a yellow planar salt 4 formulated as [RuIICp(2,2′-bipyridine)(p-benzoquinone)]BF4 in which the olefin moiety of p-benzoquinone coordinated to the RuIV center in η2-form. Salt 4 was also synthesized by the reaction of bromoruthenocenium (BF4) with p-benzoquinone and 2,2′-bipyridine in CH3NO2. The crystal of 4 was found to be monoclinic, space group P21, a = 8.516(3), b = 9.934(4), c = 11.995(4) Å, β = 103.78(1)°, V = 985.6(6) Å3, Z = 2, and the final R = 0.040 and Rw = 0.050. The same p-Bq/BF3 oxidation of osmocene gave an orange red salt 5 formulated as [Cp2OsIVFBF3]BF4 in which one of the F− atom of the BF4− ion coordinated to the OsIV center. The crystal of 5 was found to be monoclinic, space group P21/c, a = 8.065(1), b = 12.048(1), c = 16.730(2) Å, β = 94.497(8)°, V = 1620.6(3) Å3, Z = 4, and the final R = 0.055 and Rw = 0.070.
The γ-Silicon Effect. I. Solvent Effects on the Solvolyses of 2,2-Dimethyl-3-(trimethylsilyl)propyl and 3-(Aryldimethylsilyl)-2,2-dimethylpropyl p-Toluenesulfonates
Authors: Nakashima Tohru , Fujiyama Ryoji , Fujio Mizue , Tsuno Yuho 
Published: December 2003

Abstract
The solvolysis rates of 2,2-dimethyl-3-(trimethylsilyl)propyl and 3-(aryldimethylsilyl)-2,2-dimethylpropyl p-toluenesulfonates were measured in a wide variety of solvents at 45 °C. The solvent effects were analyzed by using the Winstein–Grunwald equation. The solvent effects observed did not give simple linear correlations with the 2-adamantyl YOTs parameter, but showed dispersion behavior in a series of binary solvents. The m values of 0.59—0.67 were remarkably lower than unity for the limiting kc solvolysis of 2-adamantyl p-toluenesulfonate. The deviation patterns could not be interpreted in terms of nucleophilic assistance by the solvent. The dispersion behavior with reduced m values was found to be more significant for the 3-(aryldimethylsilyl) than for the 3-(trimethylsilyl) derivatives and was compatible with the delocalization of the incipient cationic charge by participation of the Si–Cγ bond in the rate-determining step. An extended dual-parameter treatment, log (k/k80E) = mcYOTs + mΔYΔ, successfully correlated such γ-silyl assisted solvolyses. The MΔ values of 0.24—0.49 so obtained, where MΔ = 0.51mΔ/(mc + 0.51mΔ), are a measure of the extent of charge delocalization, suggesting that the γ-silyl group in the percaudal interaction is more effective in delocalizing the cationic charge than the alkyl group in C–C σ-participation, but less so than π-assisted interaction by the β-aryl group.
Three New Quassinoid Derivatives and Related Compounds as Antitumor Promoters from Brucea javanica
Authors: Rahman Shakila , Fukamiya Narihiko , Tokuda Harukuni , Nishino Hoyoku , Tagahara Kiyoshi , Lee Kuo-Hsiung , Okano Masayoshi 
Published: December 2003

Abstract
Three new quassinoid derivatives [desmethyl-brusatol (1), desmethyl- bruceantinoside A (2), and butyl ester (3) of bruceoside D (6)] were isolated from the extract of Brucea javanica. Their structures were elucidated by spectral evidence and chemical transformation to or from known compounds. The three new quassinoid derivatives and related compounds have shown inhibitory effects against TPA-induced Epstein–Barr virus early antigen (EBV-EA) activation.