bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solution Equilibria of Histidine-containing Ternary Amino Acid–Copper(II) Complexes in 20 v/v% Dioxane–Water
Authors: Yamauchi Osamu , Takaba Toshikazu , Sakurai Takeshi 
Published: July 2006

Abstract
Equilibria of histidine-containing ternary amino acid–copper(II) systems have been investigated by potentiometric titration in acid–neutral solution in 20 v/v% dioxane–water containing 0.1 M KNO3 (1 M=1 mol dm−3) at 25 °C. The stability constants of the binary complexes of histidine (his) and other amino acids (A) with a polar or a nonpolar side chain (A: serine, threonine, homoserine, asparagine, glutamine, citrulline, glycine, alanine, or valine) and the ternary complexes Cu(his)(A) have been calculated by the method of nonlinear least-squares. The overall stability constants for CuA, CuA2, and Cu(his)(A) are higher than the values reported for the corresponding complexes in water, those for Cu(his) and Cu(his)2 remaining unaffected. The stability constants (logβ1110) for Cu(his)(A) are in the range 17.4–18.0, no difference in stability being observed between the diastereomers Cu(l-his)(l-A) and Cu(d-his)(l-A). Species distribution as a function of pH reveals that Cu(his)(A) predominates in the neutral region. The stability constants have been compared with various theoretical values and found to be higher than the statistically estimated ones.
Photochemical Transformations of 1,2-Diketones and Benzhydrylamine
Authors: Mehrotra Kailash Nath , Pandey Ganesh Prasad 
Published: July 2006

Abstract
Photolysis of a mixture of substituted 1,2-diketones and benzhydrylamine (in 1:2 mole ratio) in benzene gave N-benzhydrylidenebenzhydrylamine, N-(diarylmethyl)benzamides, acyloins (3), N-(arylmethylene)benzhydrylamines, and benzophenone separated by fractional crystallization and column chromatography. The products have been characterised by analytical and spectral (IR, UV, and NMR) data and the structural assignments confirmed by the comparison (IR spectra and undepressed mixed mp) with authentic samples. Acyloins (3) are precursors for N-(diarylmethyl)benzamides and N-(arylmethylene)benzhydrylamines. A tentative mechanistic route for the formation of products has been suggested.
Preparation of New Nitrogen-bridged Heterocycles. A Facile Synthetic Method of Pyrano[2,3-b]indolizinone Derivatives
Authors: Kakehi Akikazu , Ito Suketaka , Nakanishi Kazunori , Watanabe Kozo , Kitagawa Masahiko 
Published: July 2006

Abstract
Pyrano[2,3-b]indolizinone derivatives were formed in 18–98% yields by the reactions of 3-[bis(alkylthio)methylene]-2,3-dihydroindolizin-2-ones with various acetates in the presence of alkali. Dihydroindolizinones were readily obtained by the alkaline treatment of 1-[2,2-bis(alkylthio)-1-ethoxycarbonylvinyl]-2-ethylpyridinium iodides and -2-methylpyridinium iodides or by the S-alkylation of 3-[(alkylthio)mercaptomethylene]-1-phenyl-2,3-dihydroindolizin-2-ones with alkyliodides.
The Synthesis of 2-Imino-2,3-dihydro-1,3,4-selenadiazole Derivatives
Authors: Takahashi Masahiko , Kurosawa Michiyoshi 
Published: July 2006

Abstract
The reaction of phenacyl selenocyanate with arenediazonium chlorides afforded 3-aryl-5-benzoyl-2-imino-2,3-dihydro-1,3,4-selenadiazoles, which were then acetylated and nitrosated to give the corresponding 2-acetylimino and 2-nitrosoimino derivatives respectively.
High Temperature Hard Anodizing with Tartaric Acid–Oxalic Acid–Triethanolamine Bath
Authors: Fukuda Yoshio , Fukushima Toshiro 
Published: July 2006

Abstract
Tartaric acid does not produce uniform films on A6063 alloy (Al–Mg–Si). Uniform films are formed when oxalic acid is added to the tartaric acid bath, but hardness above Hv 400 cannot be obtained at a voltage below 100 V. When 1 mol dm−3 tartaric acid–0.4–0.6 mol dm−3 oxalic acid baths were adjusted with triethanolamine (0.26–0.54 mol dm−3) to pH 1.00 and 1.25, crack-free films with hardness above Hv 430 were formed at 40 °C in the range 65–85 V. The hardness of the film is independent of the anion content of the film, increasing with increase in the thickness of cell wall and lowering in porosity.
Studies of Spin Labeled Sodium Dodecyl Sulfate. I. Synthesis and Properties
Authors: Yamaguchi Takeo , Yamauchi Akira , Kimoto Eiji , Kimizuka Hideo 
Published: July 2006

Abstract
Nitroxide spin labeled surfactant, sodium salt of 2-ethyl-2-[9-(hydroxysulfonyloxy)nonyl]-4,4-dimethyloxazolidin-3-yloxyl, was synthesized and some properties of the compound were studied by means of ESR and conductivity measurements. From conductivity measurements it was found that the critical micelle concentration of the compound was 21.6 mmol kg−1 at 25.0±0.1 °C and the micelle consisted of a small number of labeled surfactant ions. The ESR spectra of the labeled surfactant were measured as a function of concentration and temperature. These spectra showed a typical pattern interpreted in terms of spin exchange. Regarding spin exchange as chemical reaction, second order rate constant was determined from the analysis of line width and compared with the values obtained by diffusion controlled model.
Structures and Properties of 5-Substituted Cytosines. II. The Crystal Structure of 5-Methylcytosine Hemihydrate
Authors: Takenaka Akio , Kato Masuhiro , Sasada Yoshio 
Published: July 2006

Abstract
The crystal structure of 5-methylcytosine hemihydrate has been determined by an X-ray analysis to investigate the substitution effect on the cytosine moiety. The space group is C2/c, with unit-cell dimensions a=17.832(4), b=8.261(2), c=10.641(3) Å, β=125.12(1)°, and Z=8. The hydrogen bonding scheme is quite different from that of cytosine, its monohydrate, 5-bromocytosine, and its dioxane hemi-solvate. This is ascribed to the packing effect of the methyl group. A comparison with the cytosine structure indicates some deviations in bond lengths and angles, which are due to the steric and electronic effects caused by methylation. The similar values of the C(2)–N(3)–C(4) angle in cytosine and 5-methylcytosine can be related to a resemblance of their pKa values.
Pseudo-sugars. 5. Synthesis of Dl-Validatol and Dl-Deoxyvalidatol, and Their Epimers
Authors: Ogawa Seiichiro , Toyokuni Tatsushi , Omata Masaji , Chida Noritaka , Suami Tetsuo 
Published: July 2006

Abstract
New cyclitols, validatol and deoxyvalidatol, derived by hydrogenolysis of antibiotic validamycin A, were synthesized as the racemates from readily available tri-O-acetyl-(1,3/2,4,6)-4-bromo-6-bromomethyl-1,2,3-cyclohexanetriol.
The Acid-catalyzed Reaction of the 2-Oxabicyclo[4.1.0]hept-3-en-5-one System: Isomerization from Homo-4-pyrones into 2-Furylacetone Derivatives
Authors: Yamaoka Hiroshi , Mishima Ikuhiro , Miyamoto Mitsuko , Hanafusa Terukiyo 
Published: July 2006

Abstract
The monocyclopropanation of 4-pyrones with dimethyloxosulfonium methylide, using a dimethyl sulfoxide hexamethylphosphoric triamide medium in place of neat dimethyl sulfoxide, gave homo-4-pyrone derivatives, which were then rearranged into the 2-furylacetone derivatives, along with hydra ted triketones or the dehydrated naphtho[2,1-b]furan derivative, by means of strong acid catalysis at room temperature.
An X-Ray Photoelectron Spectroscopic Study of Several Hydroxy Azo Compounds
Authors: Yoshida Tooru 
Published: July 2006

Abstract
The tautomerism of several solid hydroxy azo compounds has been examined by X-ray photoelectron spectroscopy. It has been found that the proportion of enol and keto tautomers may be readily estimated from the relative intensities of the two peaks in the O(1s) electron spectrum which corresponds to the protonated and deprotonated oxygen atoms. The resonance structures of the sodium salt of 1-phenylazo-2-naphthol and 5-phenylazo-8-quinolinol have been discussed on the basis of the N(1s) and O(1s) electron binding energies.
The Isomerization of 1-Butene over the ReO3 Catalyst
Authors: Yamaguchi Tsutomu , Tsuda Nobuo , Tanabe Kozo 
Published: July 2006

Abstract
The catalytic activity of the single crystals of ReO3 was examined by using the isomerization of 1-butene as a test reaction. The results indicate that there are two types of surfaces: one is sensitive to the introduction of hydrogen, and the other is not.
The Polarographic Reduction of Various Ammonium Cations in Hexamethylphosphoric Triamide
Authors: Sakura Yachiko , Nakata Ryuji , Fujinaga Taitiro 
Published: July 2006

Abstract
The reductions of tetradecylammonium, tetradodecylammonium, benzyldimethyl(tetradecyl)ammonium, and ammonium ions were examined in hexamethylphosphoric triamide. The reduction behavior of these ions was found to be a function of the size and the charge of the cation of the supporting electrolytes.
Selective Decarboxylation of 1-Methyl-4,5-imidazoledicarboxylic Acid
Authors: Takahashi Kazuyuki , Mitsuhashi Keiryo 
Published: July 2006

Abstract
The selective decarboxylation of 1-methyl-4,5-imidazoledicarboxylic acid was carried out in various solvents. 1-Methyl-5-imidazolecarboxylic acid was obtained by heating in acetic or propionic anhydride, whereas 1-methyl-4-imidazolecarboxylic acid was obtained in N,N′-dimethylformamide, N,N′-dimethylacetamide, or N-methylpyrrolidone or by pyrolysis. The reaction mechanism is discussed.
Asymmetric Synthesis of Aspartic Acid by Hydrogenation of Optically Active 1,4-Oxazine Derivative
Authors: Tamura Minoru , Harada Kaoru 
Published: July 2006

Abstract
The asymmetric hydrogenation of an optically active heterocyclic compound, (R)-3-methoxycar-bonylmethylene-5-phenyl-3,4,5,6-tetrahydro- 2H-1,4-oxazin-2-one(2), was studied. The compound 2 was hydrogenated with several catalysts, and was converted into optically active aspartic acid. The configuration of the resulting aspartic acid proved to be (S), and the optical yield was in the range 19–170%.
Coordinative Role of Alkali Cations in Organic Reactions. IV. Benzoylation, Phenacylation, and Benzylation of Kojic Acid
Authors: Poonia Narinder S , Arora Ashok k , Bajaj Amritlal V 
Published: July 2006

Abstract
Using kojic acid (5-hydroxy-2-hydroxymethyl-4-pyrone) as a substrate, the title reactions were carried out with various alkali metal hydroxides. Whereas phenacylation (with KOH or NaOH) and benzylation (with KOH, NaOH, or LiOH) are possible only on the phenolic hydroxyl, benzoylation can be carried out selectively as well as collectively on both the hydroxyl group (in 80% aq EtOH). The results were discussed in terms of the interactive role of alkali cations with the substrate.
The Thermal Cycloaddition of Dispiro[2.2.2.2]deca-4,9-diene to Isolated Carbon-Carbon Multiple Bonds
Authors: Shibata Tohru , Tsuji Takashi , Nishida Shinya 
Published: July 2006

Abstract
The cycloadditions of dispiro[2.2.2.2]deca-4,9-diene (1) to isolated carbon-carbon multiple bonds have proceeded in two different modes, giving dispiro[2.2.4.2]dodeca-4,11-diene and tricyclo[6.4.0.03,6]dodeca-2,7-diene derivatives. Mono- and 1,2-disubstituted olefins and acetylenes gave the former adducts, whereas 1,1-disubstituted olefins gave the latter, as the major products. Evidence for the intermediacy of biradicals is provided. The observed difference in the mode of the cycloaddition is explained in terms of the stereoelectronic and/or steric effects in the transition state for the cyclization of the intermediate. The addition of 1 to tetracyanoethylene (TCNE) in wet acetone has proceeded via a zwitterionic intermediate(s), giving a 1:1:1 adduct of 1, TCNE, and water.
Vinyl Polymerization. 393. Radical Polymerization of Vinyl Monomer Initiated by Aliphatic Aldehyde
Authors: Ouchi Tatsuro , Murayama Noriyuki , Imoto Minoru 
Published: July 2006

Abstract
The homogeneous polymerization of methyl methacrylate (MMA) initiated with butanal (PrCHO), pentanal (BuCHO), and hexanal (C5H11CHO) was carried out in dioxane. It was found that the rate of polymerization can be expressed by Rp=k[MMA]1.5[RCHO]0.5. The polymerization was confirmed to proceed through a radical mechanism. Overall activation energies, when PrCHO, BuCHO, and C5H11CHO were used, were estimated to be 37.2, 36.3, and 36.0 kJ mol−1, respectively. Instead of MMA, many kinds of vinyl monomer were applied. Various methacrylates and acrylates could be polymerized, but not styrene and acrylonitrile. The effect of solvent on the rate of polymerization was studied.
A Valence Structural Study of the Electronic Structure of S2N2
Authors: Fujimoto Hiroshi , Yokoyama Takashi 
Published: July 2006

Abstract
A valence structural analysis of S2N2 has been performed within the framework of the INDO approximation. The fractional double-bond character has been suggested to be the consequence of the interaction between nonionic and ionic structures, counterbalanced in part by the overlap repulsions in the ring.
ON THE ESSENTIAL OIL OF TAIWANIA CEDAR
Authors: Kafuku Kinzo , Kato Ryo 
Published: July 2006

Abstract
1. The wooden chips of Taiwania Cryptomerioides, Hayata, gives on steam distillation 0.23% of an oil, consisting chiefly of sesquiterpene and sesquiterpene alcohol.
2. The sesquiterpenes in the oil are chiefly cadinene, with a little humulene and caryophyllene.
3. From the cadinene, a new oxidation product C12H22O2 (m.p.=142°–143°) was obtained.
4. The sesquiterpene alcohol in the oil, to which the authors suggest the name “taiwanol,” closely resembles cadinol of Semmler and Jonas. From cadinol no crystalline phenyl urethane could be obtained, but in case of taiwanol, it affords a crystalline pheyl urethane melting at 134°–135°, and furthermore, it gives a neutral oxidation product (m.p. 170°) if oxidized with permanganate in acetone solution.
Enzymatic Reactions in Aqueous-Organic Media. XVII. Optical Resolution of Amino Acid Esters by Enzymatic Hydrolysis in Organic Solvents
Authors: Tomiuchi Yoshimasa , Ohshima Kouji , Kise Hideo 
Published: July 2006

Abstract
Enantiospecific hydrolysis of Dl-tyrosine ethyl ester was carried out using α-chymotrypsin (CT) as a catalyst in organic solvents, and l-tyrosine was obtained with high optical purity. Activity and enantiospecificity of CT were found to be greatly altered by water content in the reaction media, and generally high enantiospecificity was observed at low water contents. Many of natural and unnatural amino acid esters were resolved by hydrolysis in organic solvents using CT, subtilisin Carlsberg, or subtilisin BPN′ as catalysts.
Improved Synthetic Methods of Firefly Luciferin Derivatives for Use in Bioluminescent Analysis of Hydrolytic Enzymes; Carboxylic Esterase and Alkaline Phosphatase
Authors: Toya Yoshiaki , Takagi Masaharu , Kondo Tadao , Nakata Hisao , Isobe Minoru , Goto Toshio 
Published: July 2006

Abstract
Improved synthetic methods of firefly luciferin derivatives, such as 6-O-alkanoylluciferins and 6-O-phosphonoluciferin, are described. These derivatives proved to be useful as substrates for the bioluminescent assay of hydrolytic enzymes such as carboxylic esterase and alkaline phosphatase. The synthetic methods previously reported gave fairly low yields because of direct derivatization of unstable luciferin itself and are difficult to be applied to large-scale synthesis because of unavoidable HPLC purification. We first modified the hydroxyl group of 2-cyano-6-hydroxybenzothiazole and then condensed the resulting stable products with d-cysteine to give the appropriate derivatives in good yields without HPLC purification. 6-O-Phosphonoluciferin was unstable as free acid form but stable as its sodium salt.
A Novel Ring Transformation of 3a,5,6a-Triaryl-3,3a-dihydro-2H-furo[3,2-b]pyrrole-2,6(6aH)-diones into 3-Aroyl-2,5-diarylpyrrole Derivatives
Authors: Mataka Shuntaro , Suzuki Hiroshi , Uehara Kazuko , Tashiro Masashi 
Published: July 2006

Abstract
Under aqueous conditions dimethylamine, piperidine, and triethylamine catalyzed the ring-transformation reaction of triaryl-2H-furo[3,2-b]pyrrole-2,6(6aH)-diones (1), giving benzoylhydroxy-1-pyrrolines 2, which afforded benzoylpyrroles 3 upon acid-catalyzed dehydration. The lactone-ring-opened amides 6 were obtained in the reaction of 1 with methylamine, pyrrolidine, piperidine, and perhydroazepine at room temperature in ethanol. Pyrrolidine and piperidine produced pyrrolecarboxamides 7 when the reaction was carried out in aqueous ethanol under reflux. Amides 6 afforded 7 upon treatment with the amines under the above-mentioned conditions.
Synthetic Study on Lipoteichoic Acid of Gram Positive Bacteria. I. Synthesis of Proposed Fundamental Structure of Streptococcus pyogenes Lipoteichoic Acid
Authors: Fukase Koichi , Matsumoto Takahiro , Ito Naoko , Yoshimura Takuya , Kotani Shozo , Kusumoto Shoichi 
Published: July 2006

Abstract
Synthetic study on Streptococcus pyogenes lipoteichoic acid (LTA) which was reported to induce nontoxic TNF is described. The proposed fundamental structure of LTA was constructed by coupling of the glycolipid part with the poly(glycerol phosphate) (PGP) part and subsequent deprotection. The PGP part was prepared by a simple repeating procedure using the phosphoramidite method for the construction of 1,3-phosphodiester-linkage. The glycolipid part was synthesized using appropriate glycosyl fluorides as donors, where the p-nitrobenzyl group was successfully applied to temporary protection of a hydroxyl function.
Spectroscopic Analysis and Geometry Assignment of the Minimum Energy Conformations of 2-Phenoxypyridines and Diphenyl Ethers
Authors: Uno Bunji , Kawakita Toshio , Kano Kenji , Ezumi Kiyoshi , Kubota Tanekazu 
Published: July 2006

Abstract
The conformational preferences of 2-phenoxypyridines and diphenyl ethers were determined by minimum-energy optimization using the method of ab initio molecular orbital calculations with STO-3G basis sets, and by spectral measurements and their analyses based on CNDO/S-CI calculations. The o,o-disubstituents of the methyl groups to diphenyl ether and 2-phenoxypyridine, i.e., 1,3-dimethyl-2-phenoxybenzene and 2-(2,6-xylyloxy)pyridine, respectively, prefer a symmetric skew conformation. The conformation of unsubstituted diphenyl ether (1a) is nonrigid with a dihedral angle, about 90°, of two phenyl rings at room temperature. Spectral observations at 77 K have provided evidence for this conclusion. On the other hand, 2-phenoxypyridine (2a) has been found to possess sufficient internal barriers to stabilize the two aromatic rings in a skew form. The weak nuclear repulsion, compared with that in 1a, would mainly contribute to stability in the skew form. The characteristic 1La band observed for 2a is attributed to the configuration interaction of the n–π* excited state to the 1La states in the skew form.
Hydrates of Organic Compounds. XVII. The Effect of Cations on the Formation of Hydrates of Poly(tetraisopentylammonium acrylate)
Authors: Nakayama Haruo , Yamada Ryoichi 
Published: July 2006

Abstract
A thermal analytic method using a differential scanning calorimeter was applied to binary mixtures of water with a series of poly(tetraisopentylammonium acrylates) whose cation was partially substituted by such cations as Na+, (n-C3H7)4N+, and (n-C4H9)4N+ (Cx[(i-C5H11)4N]1−xPA; C=Na, (n-C3H7)4N, and (n-C4H9)4N; x = 0.1–0.9; PA=one unit of a polyacrylate anion). It was found that (1) when C=Na, the formation of a hydrate solid is possible, even in a system of x = 0.9, though both the dissolution temperatures and the amounts of heat absorbed to melt the hydrate solid decreased with increasing x; (2) the effect of the (n-C3H7)4N+ ion was essentially similar to that of the Na+ ion, except that the temperature at which the ice phase began to melt decreased pronouncedly with increasing x; and (3) in the case of the [(n-C4H9)4N]x[(i-C5H11)4N]1−xPA system it was concluded that the solid phase was essentially a (i-C5H11)4NPA hydrate when x was smaller than about 0.4, a (n-C4H9)4NPA hydrate when x was larger than about 0.7 and some intermediate hydrate phase when x was around 0.5.
Chemical State Analysis of Sn–Sb–O Solid Surfaces by Auger Electron Spectroscopy: Differentiation of Sb(III) and Sb(V)
Authors: Komiyama Masaharu , Yoshii Mikio , Ogino Yoshisada , Ono Takehiko 
Published: July 2006

Abstract
Chemical state analysis of Sn–Sb–O solid surfaces was performed by means of Auger electron spectroscopy (AES). Differential and numerically integrated AE spectra were curve-fitted using standard spectra obtained from pure substances. The fitting revealed, for the first time, the possibility of differentiating two antimony oxide components, Sb(III) and Sb(V), by AES. Using the AE spectral parameters obtained for these two chemical states, a correlation between the Sb AE peak positions and the average Sb oxidation number was constructed and it was applied for the determination of the average Sb oxidation state in Sn–Sb mixed oxide systems.
Synthetic and Spectroscopic Studies of Some Lanthanoid Metal Complexes of 2-Acetylpyridine Nicotinoylhydrazone
Authors: Rao Thatavarthi Ramalingeswar , Srivastava Madhu Rani 
Published: July 2006

Abstract
Lanthanoid metal (Ln) complexes of the types, [Ln(Hapnh)2Cl2]Cl·nH2O and [Ln(apnh)3] have been prepared by reacting 2-acetylpyridine nicotinoylhydrazone (abbreviated to Hapnh) with hydrated lanthanoid metal chlorides. These complexes have been characterized by elemental analysis, molar conductance, magnetic susceptibility, electronic, infrared, NMR, and mass spectral studies. Various spectral parameters have been calculated from the electronic spectra of praseodymium(III), neodymium(III), samarium(III), and dysprosium(III) complexes while the neodymium(III) complexes have been subjected to detailed investigations with respect to the hypersensitive band profile and its oscillator strength’s dependence on temperature and pH. On the basis of IR and NMR spectral studies, Hapnh is believed to act as a neutral tridentate species in the adduct complexes and as a uninegative tridentate one in the neutral complexes. Electrical conductance data indicate 1 : 1 electrolytic nature of the adducts and nonelectrolytic nature of the neutral complexes. On the basis of these studies, eight- and nine-coordination numbers have been proposed around Ln(III) in the [Ln(Hapnh)Cl2]Cl·nH2O and [Ln(apnh)3] respectively.
Chromatographic Separation of α-Amino Acids on Antimony(V) Phosphate–Silica Gel ‘G’ Plates from Some Synthetic Mixtures and Drug Samples
Authors: Varshney Krishna Gopal , Khan Asif Ali , Maheshwari Sanjiv Mohan , Gupta Upma 
Published: July 2006

Abstract
Thin-layer chromatography of α-amino acids has been performed on the antimony(V) phosphate-silica gel ‘G’ plates in different aqueous, nonaqueous, and mixed solvent systems. The study has resulted into the separation and determination of amino acids from their mixtures of the same type such as acidic from acidic, and neutral from neutral. Separations of basic amino acids from neutral and acidic amino acids have also been made. The method has been utilized for the quantitative separation of amino acids from two drugs namely ‘Astymin Forte’ and ‘Santevini (Plus)’.
A New Synthesis of 5-Substituted 3-Methyl-2-phenylthio-2-penten-5-olides
Authors: Su Huiwen , Shirai Kozo , Kumamoto Takanobu 
Published: July 2006

Abstract
Dienolate 11, which was produced from 3-methyl-2-phenylthio-2-butenoic acid (1) and two equivalents of LDA, reacted with aldehydes or ketones to give 5-alkyl-3-methyl-2-phenylthio-2-penten-5-olides (12) in good yields.
Crystal and Molecular Structure of 3,6-Dioxograyanotoxin I
Authors: Sato Mamoru , Katsube Yukiteru , Katai Masaaki , Katakawa Jun’ichi , Tetsumi Tadahiro 
Published: July 2006

Abstract
The structure of 3,6-dioxograyanotoxin I ((14R)-14-acetoxy-5,10,16-trihydroxygrayanotoxane-3,6-dione) is based on four rings with various conformations. The mutual ring junction of the molecule is the same as that of grayanotoxin I.