bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetric Carbonyl Addition and Asymmetric Polymerization Assisted by Axially Chiral Diamines Give Disparate Ligand/Product Configurational Correlations
Authors: Kanoh Shigeyoshi , Muramoto Hiroki , Maeda Kazunobu , Kawaguchi Naotaka , Motoi Masatoshi , Suda Hiroshi 
Published: July 2006

Abstract
Organolithium reagents complexed with axially chiral biphenyl-substituted N,N,N′,N′-tetramethylethylenediamines (1 and 2) add to aldehydes in good enantioface selectivity. The pattern of the stereoselection, however, disagrees with that of the helical choice observed for the asymmetric polymerization of triphenylmethyl methacrylate with the same complexes.
Vacuum Sublimation Behavior of Molybdenum(VI) and Tungsten(VI) Chelates with 8-Quinolinol
Authors: Honjo Takaharu , Kawasaki Sumiko 
Published: July 2006

Abstract
A vacuum sublimation apparatus with a continuous-temperature gradient (30–280 °C) along the glass tube (60–0 cm) at 10−2 and 10−1 Torr (1 Torr=133.322 Pa) was used. 8-Quinolinol (Oxine, ox) and its Mo6+ and W6+ chelates (MoO2(ox)2 and WO2(ox)2) in milligram amounts were sublimed without any thermal decomposition. The Mo6+ chelate (orange yellow) forms large, rectangular crystals in the crossed state, while the W6+ chelate (pale yellow) forms small, rectangular crystals in the scattered states after vacuum sublimation.
Reaction of Rifamycin S with Hexahydro-1,3,5-triazines Prepared from Formaldehyde and Primary Aliphatic Amines
Authors: Taguchi Masahiro , Aikawa Norio , Tsukamoto Goro 
Published: July 2006

Abstract
Rifamycin S (1) and 25-O-deacetylrifamycin S reacted with 1,3,5-tri-t-butylhexahydro-1,3,5-triazine to give deep-blue compounds. The structures of the deep-blue compounds are discussed based on 13C NMR data, and it is concluded that the earlier structures should be partly re-revised. The mechanism of formation of the deep-blue compounds and the reaction of 1 with several hexahydro-1,3,5-triazines, which were prepared from formaldehyde and primary aliphatic amines, are also described.
Interference Effects of Helium on Motion of Xenon in Micropores of 5A Zeolites
Authors: Yasuda Yusuke , Shinbo Satoshi 
Published: July 2006

Abstract
Striking interference effects of He molecules on the motion of Xe in micropores of 5A zeolites have been found by the frequency response method. Results of the systems reveal that the absorbed Xe molecules may be divided into two abspecies, c1′ and c2′, in the presence of He molecules which were inert in a single component system: (i) at 273 K, c1′ diffuses faster and c2′ slower than pure Xe; (ii) at 255 K, c1′ diffuses faster than pure Xe, while the motion of c2′ is regarded as not diffusion but adsorption. The interference effects at 273 K have been explained quantitatively by decoupling a more general form of Fick’s law containing cross terms.
Excited-State Reactions of Coumarins in Aqueous Solutions. VI. Fluorescence Quenching of 7-Hydroxycoumarins by Chloride Ions in Acidic Solutions
Authors: Moriya Tetsuo 
Published: July 2006

Abstract
The fluorescence behavior of 7-hydroxycoumarin and 7-hydroxy-4-methylcoumarin has been studied in acidic aqueous solutions by changing the concentration of chloride ions as a fluorescence quencher. The intensity decrease and lifetime change in fluorescence from neutral and tautomeric forms of photo-excited states are explained by an interaction between protonated molecules generated in excited state and chloride ions. The magnitude of quenching-rate constant is estimated under steady-state conditions and the result is compared with the analysis using time-dependent response.
Dehydrooligopeptides. VIII. Convenient Syntheses of Various Dehydrotyrosine Derivatives Protected with Useful N, O-Protecting Groups via N-Carboxy Dehydrotyrosine Anhydrides
Authors: Shin Chung-gi , Yonezawa Yasuchika , Obara Takumi , Nishio Hiroaki 
Published: July 2006

Abstract
Various N-benzyloxycarbonyl (Cbz) O-protected dehydrotyrosine (ΔTyr) esters have been successfully synthesized mainly via two routes, in which reactions of (diethoxyphosphinyl)glycine ester with p-substituted benzaldehyde were included. Subsequent hydrolyses of the esters under various alkaline conditions were carried out in order to produce corresponding Cbz-ΔTyr-OH derivatives, which were further converted with thionyl chloride to give N-carboxy dehydrotyrosine anhydrides [ΔTyr·NCA]. In addition to these topics, the transformation of ΔTyr·NCA to various kinds of ΔTyr derivatives and a discussion on the configurational determination of all the new compounds are presented.
Liquid-Phase Dehydrogenation of 2-Propanol by Suspended Nickel Fine-Particle Catalyst
Authors: Noda Michio , Shinoda Sumio , Saito Yasukazu 
Published: July 2006

Abstract
Nickel fine particles that were prepared by a gas evaporation method were used to catalyze the liquid phase dehydrogenation of 2-propanol efficiently in the suspended state. Rate retardation due to the product acetone without catalytic-site deactivation was confirmed kinetically. High reaction rates were attained under the boiling conditions and a reasonable activation energy as well as adsorption heat of acetone was obtained. A useful application of the present catalytic process is proposed.
Diene-Transmissive Hetero Diels–Alder Reactions of 3-Oxo-1,4-pentadiene Equivalents Leading to Functionalized 2-Chromanones
Authors: Wada Eiji , Kanemasa Shuji , Tsuge Otohiko 
Published: July 2006

Abstract
Through hetero Diels–Alder reaction with a vinyl ether and Horner–Emmons olefination, diethyl 2-oxo-3-butenylphosphonate leads to 2-ethoxy-6-(1-alkenyl)-3,4-dihydro-2H-pyrans which are further transformed into 2-chromanones via regioselective Diels–Alder reactions with activated acetylenes followed by hydrolysis and oxidation.
Epoxidation of Alkenes Catalyzed by Iron(III) Schiff Base Chelates. A Monooxygenase Model
Authors: Jacob Mathew , Bhattacharya Pabitra Krishna , Ganeshpure Pralhad A , Satish Sheo , Sivaram Swaminathan 
Published: July 2006

Abstract
Iron(III) Schiff base chelates [Fe2(PA2ppd)2Cl4]Cl2 (1), [Fe2(PA2mpd)2Cl4]Cl2 (2), and [Fe(PA2opd)Cl2]Cl (3), were synthesized, where (PA2ppd), (PA2mpd), and (PA2opd) are the Schiff bases derived from 2-pyridinecarbaldehyde (PA), and p-phenylenediamine (ppd), m-phenylenediamine (mpd), and o-phenylenediamine (opd) respectively. The complexes 1, 2, and 3 catalyzed the epoxidation of alkenes with iodosylbenzene as an oxidant providing a chemical model for cytochrome P-450. The binuclear complexes (1, 2) were superior to the mononuclear complex (3) as the catalyst for epoxidation of norbornene. Addition of pyridine bases increased the rates, and yields of epoxidation.
Halogenation Using Quaternary Ammonium Polyhalides. XVII. Iodination of Acetanilide Derivatives with Benzyltrimethylammonium Dichloroiodate and Zinc Chloride
Authors: Kajigaeshi Shoji , Kakinami Takaaki , Watanabe Fumiko , Okamoto Tsuyoshi 
Published: July 2006

Abstract
The reaction of acetanilide derivatives with benzyltrimethylammonium dichloroiodate in acetic acid in the presence of ZnCl2 at room temperature or at 70 °C gave iodo-substituted acetanilide derivatives in good yields.
A 3-Methylene-1,2-dioxetane as a Possible Chemiluminescent Intermediate in Singlet Oxygenation of Allene
Authors: Akasaka Takeshi , Fukuoka Koichiro , Ando Wataru 
Published: July 2006

Abstract
Photosensitized oxygenation of bis(adamantylidene)methane and vinylideneadamantane at −78 °C afforded adamantanone and the former also emitted light when warmed up to room temperature in the presence of a fluorescer. A 3-methylene-1,2-dioxetane as a possible chemiluminescent intermediate is proposed.
Light-Induced Generation of Charge Carriers in Porphyrin Solids Doped with Electron-Accepting and Donating Molecules
Authors: Harima Yutaka , Yamamoto Kazuyo , Takeda Kazuhiko , Yamashita Kazuo 
Published: July 2006

Abstract
Fluorescence and photocurrent generation efficiencies of thin films of 5,10,15,20-tetraphenylporphyrin (TPP) and its zinc complex (ZnTPP) doped with electron-accepting and -donating molecules were investigated to get an insight into a charge-carrier generation in organic solid films upon irradiation. Photogeneration of charge carriers in I2-doped ZnTPP solids was found to consist mainly of a direct ionization process via an excited singlet state of ZnTPP while that in TPP solids was consistent with an exciplex formation model. From a practical view point, the doping of acceptor molecules into p-type porphyrin solids was effective to improve photovoltaic efficiencies of Al/porphyrin/Au sandwich-type cells.
Complexation of Lanthanoid(III) with Substituted Benzoic or Phenylacetic Acids and Extraction of These Acids
Authors: Hasegawa Yuko , Morita Yoko , Hase Masako , Nagata Mayumi 
Published: July 2006

Abstract
The stability constants of lathanoid(III) complexes with several benzoic and phenylacetic acids substituted with –OH, –OCH3, or –NH2 groups as well as the dissociation constants of these acids have been determined potentiometrically in 0.1 mol dm−3 sodium perchlorate solution at 25 °C. The distribution constants of these acids between the perchlorate media and chloroform and the dimerization constants in chloroform were also determined. The distribution constants of ortho-substituted benzoic acids seem to be larger than those of α-substituted phenylacetic acids with the same substituent. There is a trend that the higher the pKa, the larger the dimerization constant. The order of pKa is : o-aminobenzoic&gt;o-methoxybenzoic&gt;β-hydroxy-β-phenylpropanoic&gt;α-hydroxyphenylacetic(mandelic)&gt;α-methoxyphenylacetic&gt;o-hydroxybenzoic acid and the sequence of the stability constants of their complexes for a given lanthanoid is also in a same order except for the mandelate. Mandelic acid forms more stable complexes with the heavier lanthanoid(III) while others are similar to each other regardless of the lanthanoid.
Gel Filtration Chromatographic Study on the Micelle Formation of Triton X-100
Authors: Funasaki Noriaki , Hada Sakae , Neya Saburo 
Published: July 2006

Abstract
The aggregation properties of Triton X-100 are investigated by frontal gel (Sephadex G-200) filtration chromatography (GFC) at 25 °C and considered in the framework of the monomer–m-mer equilibrium on the basis of both asymptotic and plate theories. The analysis of GFC data by asymptotic theory yields an equilibrium constant of K=1.3×1068 (mmol dm−3)−138 and a micellar elution volume of Vm=15.30 cm3. By using this Vm value, we calculate a micellar hydrodynamic radius of 4.6 nm and the monomer concentration C1 for Triton X-100. Values of cmc=0.30 mmol dm−3 (UV at 245 nm) and 0.31 mmol dm−3 (UV at 265 nm and GFC) are determined and are very close to the cmc value theoretically calculated by using Phillips’ definition of the cmc. The C1 value above the cmc is larger than these cmc values by about 0.06 mmol dm−3. The derivative elution pattern at the trailing boundary exhibits two maxima and a minimum (Vmin), and indicates the formation of small micelles near the cmc. The concentration at Vmin on the elution curve, Cmin, is close to the cmc, as we have already predicted by both asymptotic and plate theories. The present work demonstrates the utility of these theories for analyzing the GFC pattern of self-associating systems and will serve to understand the actions of Triton X-100 on membrane bound proteins and on lipid bilayers.
Acid-Catalyzed Transformation of α-Hydroxy-γ-oxo Acetals to γ-Oxo Esters. A Novel Deconjugation of 4-Oxo-2-alkenal Acetals
Authors: Kanemasa Shuji , Nakagawa Norihiko , Suga Hiroyuki , Tsuge Otohiko 
Published: July 2006

Abstract
Under acid catalysis, α-hydroxy-γ-oxo acetals which are readily available from the nitrile oxide cycloaddition route are smoothly converted into γ-oxo esters. This unusual and high-yield transformation involves rare acid-catalyzed deconjugation of the intermediary 4-oxo-2-alkenal acetals and is influenced by a substituent at the 5-position.
Molecular Recognition in the Formation of Conglomerate Crystal. 2. The Role of Arenesulfonic Acid in the Conglomerate Crystals of Amino Acid Salts
Authors: Kimoto Hiroki , Saigo Kazuhiko , Ohashi Yuji , Hasegawa Masaki 
Published: July 2006

Abstract
The structures of conglomerate crystals, p-chlorobenzenesulfonic acid salt of l-alanine, p-toluenesulfonic acid salt of l-serine, and benzenesulfonic acid salt of l-leucine, were determined by X-ray analysis. The crystals are built up of repeating units consisting of two amine components and two acid components to form a helical column by hydrogen bonds. The arrangements of the arenesulfonic acids are found to be similar to each other in these systems. Moreover, the arrangements have similarity to those of cinnamic acid in the crystals of cinnamic acid salts of (R)-1-phenylethylamine and of (R)-1-(4-isopropylphenyl)ethylamine, which are also conglomerates. These results suggest that our proposed criteria for the choice of an achiral derivatizing agent in the transformation of a racemic compound into a conglomerate crystal is appropriate.
Anodic Oxidation of (Trimethylsilyl)methanes with π-Electron Substituents in the Presence of Nucleophiles
Authors: Koizumi Toshio , Fuchigami Toshio , Nonaka Tsutomu 
Published: July 2006

Abstract
It was found that oxidation potentials of methanes with π-electron substituents were decreased by introduction of a trimethylsilyl group. The anodic oxidation of benzyl-, allyl-, aryl(or alkyl)thiomethyl-, and aryloxymethyl-substituted trimethylsilanes smoothly proceeded in the presence of nucleophiles, e.g. alcohols and carboxylic acids, to eliminate the trimethylsilyl groups giving the corresponding alkoxylated and carboxylated products in moderate or high yields without full optimization of electrolytic conditions, while aminomethylsilanes did not undergo such a kind of anodic oxidation.
On the Relationship between the Chemical Structure and the Cyclic AMP Phosphodiesterase Inhibitory Activity of Flavonoids as Studied by 13C NMR
Authors: Sakamoto Yohko , Ohmoto Taichi , Nikaido Tamotsu , Koike Kazuo , Tomimori Tsuyoshi , Miyaichi Yukinori , Shirataki Yoshiaki , Monache F D , Botta B , Yokoe Ichiro , Komatsu Manki , Watanabe Shosuke , Ando Isao 
Published: July 2006

Abstract
The relationship between the chemical structure and the cyclic adenosine monophosphate phosphodiesterase inhibitory activity was studied regarding forty-eight flavones, thirty-five flavanones, and six isoflavones by using the 13C NMR chemical shift averaged over all aromatic carbons in a compound. The average value of potent 13C chemical shifts over the aromatic carbons active flavonoids (IC50 0.6–20.0×10−5 M/L) are within the range from δ 133.5 to δ 135.7, but those of the inactive flavonoids and the weak active flavonoids are not within this range. This means that the averaged 13C chemical shift becomes an “index” for testing the inhibitory activity. Further, the above relationship was proposed as a means for conveniently determining the inhibitory activity.
An X-Ray Diffraction Study on the Stucture of 18-Crown-6 Ether Complexes with Alkali Metal Ions in Aqueous Solution
Authors: Ozutsumi Kazuhiko , Natsuhara Masahiko , Ohtaki Hitoshi 
Published: July 2006

Abstract
The structure of 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) and its complexes with alkali metal ions in aqueous solution has been investigated by X-ray diffraction and Raman spectroscopic methods at 25 °C. The X-ray scattering data and Raman spectrum for an aqueous 18-crown-6 solution show that free 18-crown-6 has a conformation of C1 or D3d symmetry. The molecule seems to be flexible and may be present as a mixture of the two conformations in aqueous solution. The structure of the lithium complex was not conclusive because of a weak scattering power of lithium atoms and weak complex formation between lithium ion and 18-crown-6. The sodium 18-crown-6 complex is estimated to have a structure similar to that found in crystal. The 18-crown-6 ring within the complex adopts the C1 conformation, where five oxygen atoms within 18-crown-6 coordinate to sodium ion at the equatorial position and an oxygen atom within 18-crown-6 and a water molecule at the axial one. The structure of the potassium complex is also similar to that in crystal in which the D3d conformation is taken. Potassium ion is located at the center of the mean plane of 18-crown-6 and one or two water molecules solvate potassium ion above and/or below the plane of 18-crown-6. It is suggested that the structure of the caesium complex is with either C1 or D3d symmetry, where caesium ion is apart from the mean plane of 18-crown-6. The rubidium complex was not examined because of a strong fluorescent X-ray emission from rubidium atoms when studied. The 18-crown-6 ring in the sodium and potiassium complexes is rather rigid probably because the cavity of the ring well fits to the metal ions, while the ring coordinating to large caesium ion becomes more flexible than that in the sodium and potassium complexes due to weaker interaction with caesium ion.
Reactive Langmuir–Blodgett Membrane for Biosensor Applications. Use of Succinimidyl Behenoate-Based Membranes as Support for Covalently Immobilizing α-Chymotrypsin
Authors: Anzai Jun-ichi , Lee Shouryu , Osa Tetsuo 
Published: July 2006

Abstract
Succinimidyl behenoate was synthesized to prepare Langmuir–Blodgett (LB) membranes which possess reactive groups on the surface. The surface of the succinimidyl behenoate-based LB membrane could be covalently modified with α-chymotrypsin, for the purpose of biosensor applications.
Physicochemical Studies on Solid Solutions of Calcium Phosphorus Arsenic Hydroxyapatites
Authors: Mahapatra P P , Mahapatra L M , Mishra Bagmi 
Published: July 2006

Abstract
Samples of arsenic hydroxyapatite and its solid solutions with calcium hydroxyapatite are synthesized in aqueous media. The samples are characterized by X-ray, infrared spectra, the assignments of phosphate, arsenate, and hydroxyl bands are recorded. The possibility of anion migration in the apatite lattice is proposed. Presence of water, adsorbed in nature, is indicated in the TGA and DTA analysis of the samples. The solubility product, Ksp, of the samples of arsenic hydroxyapatite Ca10(AsO4)6(OH)2, and the solid solutions, Ca10(PO4)6−x(AsO4)x(OH)2, (x=1 to 5) are determined considering the formation of ion pairs [CaHAsO4]0, [CaHPO4]0, [Ca(H2AsO4)]+, and [Ca(H2PO4)]+ in solution. The instability of the samples in solution is indicated from the experimental ΔG0soln. values.
Concentrated Mixtures of 1:1 Electrolytes: Densities and Excess Volumes of Aqueous KBr with KCl and NaBr
Authors: Kumar Anil 
Published: July 2006

Abstract
Densities of aqueous KCl–KBr and NaBr–KBr mixtures are reported from the ionic strengths 0.5 to 4 mol kg−1 of water. The results are analyzed in the light of Pitzer theory of specific interactions. The deviations of experimental quantities from the Young rule (excess volumes) are discussed in terms of interactions between the ions of like charges. The excess volumes showed weak dependence on temperature.
The Thermotropic Liquid-Crystalline Behavior of Alkylammonium Benzenesulfonates and Related Salts
Authors: Ito Masato , Matsunaga Yoshio , Matsuzaki Hiroyuki , Shimojima Saeko 
Published: July 2006

Abstract
Alkylammonium benzene-, pyridine-3-, p-toluene-, and p-ethylbenzenesulfonates were found to be smectogenic when the cation carries an octyl or longer alkyl group. The thermal stability of the mesophase usually reaches its maximum at the octadecylammonium salt. The temperature range of stable existence is in the following order: pyridine-3-sulfonate&gt;p-toluenesulfonate&gt;benzenesulfonate&gt;p-ethylbenzenesulfonate, suggesting the presence of a specific interaction between the ammonium ion and the nitrogen atom in the pyridine ring.
The Reactivities of Polyaromatic Hydrocarbons in Catalytic Hydrogenation over Supported Noble Metals
Authors: Sakanishi Kinya , Ohira Masato , Mochida Isao , Okazaki Hiroshi , Soeda Mahito 
Published: July 2006

Abstract
The reactivities of several polyaromatic hydrocarbons (pyrene: P, fluoranthene: FL, anthracene: An, fluorene: F, acridine: Ac, and carbazole: C) in the catalytic hydrogenation were studied and compared over supported noble metals (Pt, Pd, Rh, and Ru on a carbon or alumina support). The specific reactivity and selectivity were found to be strongly dependent upon the combination of the catalyst species and the substrate. The catalysts exhibited the activity order of Rh &gt; Pd &gt;&gt; Pt &gt; Ru for tricyclic aromatics of An, F, Ac, and C, although the catalysts provided very variable selectivities of the partially hydrogenated products which were produced via both consecutive and competitive routes, apparently according to the type of ring-skeleton and the presence of a nitrogen atom. The reactivity of the starting substrates and intermediates are compared to the quantum chemical reactivity indices, calculated based on MNDO (modified neglect of diatomic overlap). The values of the LUMO electron density, the π-bond order, and the stability of the product appear to govern the reactivity and selectivity of the hydrogenation, depending upon the combination of the catalyst species and the substrate. No hydrogenation of a substrate proceeds when its reactivity indices are less than the threshold value, which is subject to the activity of the catalyst and the reaction conditions defining product selectivity via both competitive and consecutive schemes.
A Practical Method for Optical Resolution of 1,1′-Binaphthyl-2,2′-dicarboxylic Acid via 1-Phenylethylamides
Authors: Ôi Shuichi , Matsuzaka Yutaka , Yamashita Junzo , Miyano Sotaro 
Published: July 2006

Abstract
Both enantiomers of 1,1′-binaphthyl-2,2′-dicarboxylic acid (100% ee’s by HPLC) were conveniently obtained in high yields (ca. 80% of the theory) via fractional crystallization of the (S)-1-phenylethylamide diastereomers of the racemic acid followed by treatment with thionyl chloride and then alkaline hydrolysis.
AN YLID EXCHANGE REACTION OF SULFILIMINE
Authors: Yamamoto Tamotsu , Harigaya Yasuji , Okawara Makoto 
Published: July 2006

Abstract
The reaction of new sulfilimine, N-2,4-dinitrophenyl-S,S-dimethylsulfilimine 1, with p-toluenesulfonamide gave N-p-toluenesulfonyl-S,S-dimethylsulfilimine 2. The reaction of 1 with carbon acids 3 having active methylene gave stable S-C ylids (exchange of S-N ylid for S-C ylid), while 2 reacted with malonitrile to give S-C ylid only in low yield. Thus, the ylid exchange mechanism based on the equilibrium including the protonated sulfonium salts has been assumed.
PHOTOELECTRON SPECTRA OF ANILINES
Authors: Kobayashi Tsunetoshi , Nagakura Saburo 
Published: July 2006

Abstract
Photoelectron spectra of aniline, toluidines, N,N-dimethylaniline, and N,N-dimethyltoluidines were measured, ionization being effected by irradiation with the 584 Å helium resonance line. The assignment of the observed photoelectron spectra was made, special attention being paid upon the steric hindrance effect of o-methyl groups upon ionization potentials.
BINUCLEAR METAL COMPLEXES. V. TEMPLATE SYNTHESIS OF A BINUCLEAR COPPER(II) COMPLEX OF A MACROCYCLE CONTAINING AMIDO GROUPS
Authors: Okawa Hisashi , Honda Mitsuo , Kida Sigeo 
Published: July 2006

Abstract
A new binucleating ligand, 2,6-bis (β-aminoethylcarbamoyl)-4-methylphenol was prepared and its copper(II) complex was isolated. By the reaction of this complex and 2,6-diformyl-4-methylphenol, a binuclear copper(II) complex of a new macrocycle, 23,24-dihydroxy-10,21-dimethyl-3,6,14,17-tatraazatricyclo[17,3,1,18,12]tetracosa-1(23),6,8(24),9,11,13,19,21-octaene-2,18-dione, was synthesized.
AUTOXIDATION OF HALOGENATED METHYL THYROPROPIONATES CATALYZED BY BIS(3-SALICYLIDENEAMINOPROPYL)AMINECOBALT(II). A MODEL REACTION FOR THE METABOLISM OF THYROXINE
Authors: Nagamachi Tomoaki , Nishinaga Akira , Matsuura Teruo 
Published: July 2006

Abstract
Autoxidation of halogenated methyl thyropropionates catalyzed by bis(3-salicylideneaminopropyl)aminecobalt(II) gave rise to direct cleavage of their diphenyl ether linkage. The reaction provides a model for the enzymic degradation of thyroxine to form diiodotyrosine.