bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potential carcinostatics: Synthesis and properties of potential inhibitors of the adenylosuccinate synthetase and adenylosuccinate lyase systems
Authors: Wanner M. J. , Hageman J. J. M. , Koomen G. J. , Pandit U. K. 
Published: September 2010

AbstractTreatment of 6‐chloro‐9‐(tetrahydro‐2‐pyranyl)purine (8) with 2 equivalents of methylene triphenylphosphorane (−30°) yields the corresponding purinyl ylide 9. Reaction of the latter with ethyl glyoxylate gives the expected acrylic ester derivative 10. Ethyl (dimethylsulfuranylidene)acetate adds to the acrylic ester moiety to form a mixture of isomeric purinyl substituted cyclopropanedicarboxylic esters (11a and 12a). The ylide 9 reacts with cis‐dimethyl epoxysuccinate (13) to give the oxaphospholane derivative 14, which undergoes ring opening (DMSO, 80°) to 6‐[2,3‐(diethoxycarbonyl)‐1‐propenyl]‐9‐(tetrahydro‐2‐pyranyl)purine (15). Hydrogenation (H2/Pd) of 15 leads to the corresponding propyl derivative 17; while its treatment with base (NaH/DME) produces the tricyclic product 16. The significance of purinyl derivatives 16 and 17 (R = H) as potential inhibitors in the biosynthesis of adenosine monophosphate (AMP, 3) is discussed.
The chemistry of small ring compounds. Part 41: Methylenethiirane, an isomer of cyclopropanethione
Authors: Jongejan E. , Buys Th. S. V. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractThe cyclic carbonate 3, prepared from bis(1‐hydroxycyclopropyl) sulfide and phosgene, has been thermolysed at 500° and 0.5 mm, yielding methylenethiirane (4), an isomer of cyclopropanethione. The structure of 4 is supported by mass spectrometry, 1H‐ and 13C‐NMR and infrared (in vapour phase and in solution). Attempted reactions with methyl fluorosulfate, diazomethane, triphenylphosphine and 1,3‐diphenylisobenzofuran all lead to polymeric material of uncertain structure.
1,3,4,6‐Tetraketones. Part XVIII. Reaction of unsymmetrical 1,3,4,6‐tetraketones with lead tetraacetate: Oxidative cyclization and rearrangement into dehydroacetic acid analogues
Authors: Poje M. , Gašpert B. , Balenović K. 
Published: September 2010

AbstractOxidation of l‐phenylheptane‐1,3,4,6‐tetrone (5) with lead tetraacetate gave the dehydroacetic acid analogues 6 and 7 in 3 : 1 ratio and no traces of dehydroacetic or dehydrobenzoylacetic acids (4a and 4b). Oxidation of an equimolar mixture of the symmetrical 1,3,4,6‐tetraketones 1a and 1b with lead tetra‐acetate gave only the compounds 4a and 4b. These results can be rationalized in terms of a mechanism involving the cyclic intermediates 9 and 10 in the oxidation of 1,3,4,6‐tetraketones with lead tetraacetate.
A Model synthesis of Ring B of Warburganal and Muzigadial
Authors: Peterse A. J. G. M. , Roskam J. H. , de Groot Ae. 
Published: September 2010

AbstractThe synthesis of 1,2‐diformyl‐6,6‐dimethyl‐2‐cyclohexen‐1‐o1 from 2,2‐dimethylcyclohexanone is described.
A convenient synthesis of L‐Nτ‐methylhistidine and L‐Nτ‐ethylhistidine (Imidazole chemistry, Part IV)
Authors: Noordam A. , Maat L. , Beyerman H. C. 
Published: September 2010

AbstractInteraction of L‐histidine methyl ester (2) with N,N′‐carbonyldiimidazole gave near‐quantitative ring closure between the Nα and the Nπ function to form (7S)‐5,6,7,8‐tetrahydro‐7‐(methoxycarbonyl)‐5‐oxoimidazo[1,5‐c]pyrimidine (3). Alkylation of 3, e.g. with an alkyl halide, trialkyloxonium tetrafluoroborate or dialkyl sulfate, is then only possible at the “Nτ function” to form (7S)‐2‐alkyl‐5,6,7,8‐tetrahydro‐7‐(methoxycarbonyl)‐5‐oxoimidazo[1,5‐c]pyrimidinium salt (4). Hydrolysis of 4, aided by hydrochloric acid, afforded L‐Nτ‐alkylhistidines in high yield. The L‐Nτ‐methylhistidine (5a) was found to be identical with the costly natural amino acid and optically pure.
Addition of aldehydes to cyclooctyne under the influence of boron trifluoride. 2‐Alkylidenecyclooctanones
Authors: Verboom W. , Bos H. J. T. 
Published: September 2010

AbstractAddition of aliphatic and aromatic aldehydes 4 to cyclooctyne 5 under the influence of boron trifluoride produces (E)‐2‐alkylidenecyclooctanones 6 in good yields.
Protonation as a driving force for pentacoordination of phosphorus
Authors: van Aken D. , Castelijns A. M. C. F. , Buck H. M. , Verkade J. G. 
Published: September 2010

AbstractCNDO/2 calculations are reported on four caged phosphorus compounds, Y‐P(OCH2CH2)3X (X = N, CH; Y = O, OH+, H+). Structures with and without a transannular bond between P and X were taken into account; the influence of this bond on the stability of the compounds was examined. For X = N and Y = H+ the lowest‐energy structure corresponds with the geometry found by X‐ray analysis. If X = CH, formation of a transannular bond proves to be unlikely, as expected. The calculations predict the formation of a P‐N bond upon protonation of the phosphate (X = N, Y = O). The net atomic charges in the protonated phosphite were used to calculate its NMR coupling constant, 1JPH, which correlates well with the value found experimentally.
Biomimetic polyene cyclizations. Synthesis of racemic 19‐norprogesterone
Authors: Johnson William S. , Huffman William F. , Boots Sharon G. 
Published: September 2010

AbstractThe aim of this study was to apply biomimetic cyclization strategy to a total synthesis of racemic 19‐norprogesterone (8). Treatment of enone 1 with lithium aluminium hydride in ether afforded trienynol 2 which was cyclized with trifluoroacetic acid in methylene chloride containing ethylene carbonate to give ketone 4 as a 76/24 mixture of the 17β/17α epimers in 52% yield. Conversion of 4 to DL‐19‐norprogesterone (8) was effected in 68% yield by ozonolysis (to give 6) followed by cyclodehydration.
A convenient synthesis of human calcitonin mainly via the repetitive excess mixed anhydride method
Authors: Hirt J. , Kranenburg P. , Beyerman H.C. 
Published: September 2010

AbstractThe synthesis is described of the sequence containing 32 amino acid residues proposed for human calcitonin (HCT), presumably a thyroid hormone (Fig. 1)4.Our strategy employed the coupling of four fragments: 1–7 (with closed disulfide bridge), 8‐10, 11‐19 and 20‐32 via the azide or dicyclohexylcarbodiimide (DCCI) method. With the exception of two DCCI couplings (Asn3 and Asn17), these fragments were prepared exclusively by stepwise synthesis via the repetitive excess mixed anhydride (REMA) méthod (Fig. 2).Removal in one operation of all protecting groups with cold concentrated hydrochloric acid and chromatographic purification afforded HCT with full hypocalcemic potency (Table 1).
Synthesis of 1,7‐difunctionalized cycloheptatrienes. Complications from rapid [1,7] sigmatropic shifts of unhindered alkylthio groups
Authors: Cavazza M. , Morganti G. , Pietra F. 
Published: September 2010

Abstract4,5‐Benzotropone and 1,2‐ethanedithiol gave the expected dithioketal 8 with boron trifluoride etherate in methanol. In contrast, tropone, under similar conditions, gave the bicyclic 1,7‐disubstituted cycloheptatrienes 2, 3 and 4 on reaction with, respectively, 1,2‐ethanedithiol, 1,3‐propanedithiol, and o‐benzenedithiol. Related, monocyclic 1,7‐difunctionalized cycloheptatrienes 10–13 and 15a‐d were obtained from sodium thiolates and methoxy‐ or 1‐(alkylthio)tropenylium salts in dichloromethane‐ethanol at − 50°C. 1,7‐Bis(alkylthio)‐substituted cycloheptatrienes with unhindered alkylthio groups showed a rapid interconversion of the alkylthio groups at the C(1) and C(7) carbons (15a ⇄ 16).
Photochemistry and photophysics of a polycyclic azoalkane. Solvent and temperature effects
Authors: Turro Nicholas J. , Ramamurthy V. 
Published: September 2010

AbstractDirect photochemical excitation of the polycyclic azoalkane 1 yields a mixture of (CH)6 isomers as major products at room temperature and the 1,2‐diaza‐cyclooctatetraene 2 as the major product at − 78°C. The ratio of (CH)6 isomers to 2 is strongly dependent on solvent. For example, at room temperature the ratio (CH)6/2 is 92/8 in pentane and 38/62 in dimethyl sulfoxide. Triplet photosensitized excitation of 1 yields 2 as the major product. The triplet reaction is insensitive to temperature and solvent. These results are consistent with reaction of S1(1) to yield predominately (CH)6 isomers via a thermally activated nitrogen extrusion, whereas T1(1) yields predominantly 2 via a temperature and solvent independent rearrangement. Quantitative measurement of photochemical and photoluminescence parameters reveals that the solvent effect on the product distribution in the direct photolysis of 1 is due to a combination of the influence of solvent on the rate of reaction from S1 and the rate of intersystem crossing from S1.
Aromatic lead(IV) compounds XI. 207Pb as a probe for proton assignment in PMR spectra of aryllead(IV) compounds
Authors: de Vos D. , van Barneveld W.A.A. , van Beelen D.C. , Wolters J. 
Published: September 2010

AbstractA method of assigning PMR spectra of aryllead(IV) compounds by means of the broadly separated signals of satellites associated with the occurrence of the magnetic 207Pb species in all natural lead, is developed and thoroughly verified for series of phenyllead(IV) compounds. The utility of the method is demonstrated by the analysis of the PMR spectra of several series of substituted aryllead(IV) compounds. For this purpose 44 compounds, of which 27 are new, have been synthesized.
A novel synthetic approach to mitomycins. One step synthesis of a 5,10‐dioxo‐1H‐pyrrolo[1,2‐a]benz[f]indole
Authors: Geevers J. , Visser G.W. , Reinhoudt D.N. 
Published: September 2010

AbstractA new method for the synthesis of pyrrolo[1,2‐a]indoles, starting from enamines via 1,5‐dipolar cyclization is described. The method is considered to be useful for the synthesis of mitomycin type of compounds.
Gas‐liquid chromatography/mass spectrometry identification of previtamin D3 and vitamin D3 in the skin of vitamin D‐deficient rats irradiated with ultraviolet light
Authors: Okano T. , Mizuno K. , Matsuyama N. , Nobuhara N. , Kobayashi T. 
Published: September 2010

AbstractThe existence of previtamin D3 and vitamin D3 in the skin of vitamin D‐deficient rats irradiated with ultraviolet (UV) light has been physico‐chemically confirmed by gas‐liquid chromatography/mass spectrometry (GC/MS). The lipid extracts obtained from the UV irradiated rats' skins were purified to isolate the previtamin D3 and vitamin D3 fractions. When the isolated fractions were individually applied to GC/MS equipped with units of electron impact (EI) and chemical ionization (CI) as energy sources and mass fragmentography, the existence of previtamin D3 and vitamin D3 in the corresponding fractions was clearly identified. The experimental results showed that the endogenous 7‐dehydrocholesterol (7‐DHC) in the skin of the rat was photochemically converted to previtamin D3 in the same manner as in a test tube by UV irradiation and then the in vivo generated previtamin might be biothermally isomerized to vitamin D3 at unknown places before the physiological effects would be apparent.
Ether cleavage of isomeric 2,3‐(dimethoxycarbonyl)‐7‐oxabicyclo[2.2.1]heptanes
Authors: Eggelte T. A. , de Koning H. , Huisman H. O. 
Published: September 2010

AbstractThe ether cleavage of the three isomeric 2,3‐(dimethoxycarbonyl)‐7‐oxabicyclo[2.2.1]‐heptanes with acetic anhydride under influence of BF3 etherate or FeCl3 has been studied. A complex mixture of products was obtained, resulting from elimination, migration and substitution reactions. The results are interpreted in terms of reactions occurring via an acyloxonium ion and not via a ringopened carbenium ion intermediate.
Zur photoinduzierten Spaltung α,β‐ungesättigter γ,δ‐Epoxy‐Ester II: Der Einfluss einer Methyliden‐Gruppe in ϵ‐Stellung
Authors: Frei B. , Schweizer W. B. , Wolf H. R. , Jeger O. 
Published: September 2010

AbstractPhotoinduced cleavage of α,β‐unsaturated γ,δ‐epoxyester II: the effect of a methylidene group in ϵ‐position. On direct excitation (γ = 254 nm, pentane) 4 undergoes mainly (60%) cyclo‐elimination to give the isomeric products 7–13 and to a smaller extent (7%) 4 yields the Z‐isomer 6. On sensitization by acetone (γ > 280 nm) 4 gives the isomeric cyclobutanone 16 (22%) or isomerizes to 6 (13%).The structures of compounds 11, 13 and 16 were established by X‐ray analysis: 11: a = 7.114, b = 29.191, c = 7.784 Å, β = 68.33°, P21/c, Z = 4; 13: a = 10.732, b = 6.777, c = 19.254 Å, β = 105.39°, P21c, Z = 4; 16: a = 9.176, b = 11.115, e = 13.375 Å, β = 76.36°, P21/n, Z = 4.The allene 7 and the cyclopropene 8 are products of a carbenoid species e, whereas the cyclopropenes 9 and 10 are formed via another carbenoid species d. The spirocyclic cyclopropenes 11 and 12 as well as the tricyclic cyclopropane compound 13 are shown to be photoproducts of 9 and 10.The comparison of the results of the photolysis of 4 and 21b discloses the influence of an ϵ‐methylidene substituent on the photochemistry of the α,β‐unsaturated γ,δ‐epoxy chromophore: (a) on direct excitation selective photocleavage of the C(γ)‐O bond analogous to 2 → a is suppressed in favour of cycloelimination reactions of type 4 → d and 4 → e. In the absence of an ϵ‐methylidene substituent cycloelimination of type 4 → d does not occur; (b) on T‐sensitization photocleavage of type 2 → a is replaced by cleavage of the C(δ)‐O bond (4 → f → 16).The photochemistry of the epoxy‐ene ester 4 on direct excitation is analogous to the photochemistry of the corresponding epoxyenone 32 on π,π* excitation. From the results of the photosensitization experiments evidence is obtained for the singlet multiplicity of the cycloelimination processes of 3 and 4.
The ring inversion in cis‐cisoid‐cis‐transoid‐cis‐perhydronaphthacene
Authors: Vanhee P. , de Pessemier F. , Anteunis M. , Tavernier D. 
Published: September 2010

AbstractThe barrier (ΔG≠) to ring inversion in the title compound amounts to 56.7 kJ·mol−1 at 299 K. The inversion mechanism is discussed. The barrier was measured by dynamic 13C NMR spectroscopy. The 13C shifts of the title compound have been assigned.
A new synthesis of 4‐OR‐3‐penten‐1‐ynes (C5‐fragment) as a tool for the preparation of vitamin A
Authors: Brouwer M. S. , Hulkenberg A. , Kok J. G. J. , van Moorselaar R. , Overbeek W. R. M. , Wesselman P. G. J. 
Published: September 2010

AbstractIn our technical synthesis of vitamin A, the intermediate β‐C18‐ketone (5) is obtained in a four‐step sequence from β‐ionone (1). In order to reduce the number of reaction steps, 1 is condensed with a C5‐fragment, leading to a convergent synthesis of 5. The title compound (8) with R = ‐CH(OC2H5)‐CH3 (8i) is prepared by the reaction of 1,3‐dichloro‐2‐propanol with ethyl vinyl ether, followed by dehydrohalogenation, substitution and isomerisation of the resulting mixed acetal (17i) in a simple one‐pot procedure by treatment with sodium acetylide. The syntheses of several C5‐synthons of type 8 with different groups R are described. The condensation product of 1 and 8i is partially hydrogenated and subsequently hydrolysed to 5 in an overall yield of 85%.
Studies on the metabolism of polyphosphates in yeast cells. I. Polyacrylamide gel electrophoresis of polyphosphates
Authors: Booij H. L. , Beekes Henny 
Published: September 2010

AbstractA preliminary study was made of the usefulness of a gel electrophoresis method of polyphosphates of different chain lengths. Pre‐electrophoresis of the gels appeared to be of primary importance to get rid of substances which interfere with the detection of polyphosphates. Four detection methods have been studied, each showing its own advantages and drawbacks. Determination of the chain lengths of unknown polyphosphates is possible as there exists a linear relation between the logarithm of the chain length and the migration distance. However, added electrolytes restrict the use of this relationship. They decrease the migration velocity of the polyphosphates and alter the numerical coefficient occurring in the equation.
A new method for the determination of the dipole moment of an electronic excited state: The π of cyclohexanone and the 1La of indole
Authors: Ramos Joaquim Jose Moura , Stien Marie‐Louise , Reisse Jacques 
Published: September 2010

AbstractIn this work, a new method for the determination of a Franck‐Condon excited state moment in solution is described. This method is based both on the study of the solvatochromic effect and on the use of Onsager reaction field theory. The method we propose requires (1) calorimetric measurements of the heat of transfer from solvent S1 to solvent S2 for the solute in its ground state and for a homomorph; (2) the absorption frequencies of the solute in the two solvents and (3) experimental determination of the solute and homomorph ground state dipole moments.It is easy to show that a very simple relationship exists between these various experimental quantities if the two solvents are such that the reaction field theory can be applied to describe the dipolar part of the solvent solute interactions. The use of the homomorph method permits one to take into account the variation of the cavity term from solvent to solvent and the variation of the solute solvent dispersive energy term with the nature of the solvent. Moreover, the method does not requires neither the estimation of the cavity radius nor the dangerous assumption that the dipole is centred in the cavity. This new method, which compared to older methods, must give more reliable results, is applied to the π* state of cyclohexanone and to the 1La state of indole.
Photochemistry in solution. Photoreactivity of 2,3‐dihydro‐4H‐pyran derivatives
Authors: Chaquin Patrick , Furth Bernard , Kossanyi Jean 
Published: September 2010

AbstractSubstituted 2‐acyl‐2,3‐dihydro‐4H‐pyrans 1–5 and 7, when irradiated at 254 nm, undergo ring contraction to form 1,2‐diacylcyclobutanes and cleavage by retro‐Diels‐Alder reaction through the common intermediate 34. Excitation at 313 nm of the carbonyl 1(n,π*) state of compounds 1–5 leads to the unsaturated acetals 8–12 while the benzoyl derivative 6 gives only polymers and the aldehyde 7 undergoes decarbonylation. The same cyclisation occurs with 4‐acetylcyclohexene 28. This reaction which leads stereoselectively to the isomer in which the substituent R is exo, originates from the 1(n,π*) singlet state as demonstrated by quenching experiments. Interaction of this chromophore with the carbon‐carbon double bond is demonstrated by comparing the olefinic compounds with that of the corresponding saturated analogues.
Radical cation states of 2,3,5,6‐tetramethylenenorbornane, 2,3,5,6‐tetramethylenebicyclo[2.2.2]octane and of related compounds
Authors: Mohraz Manijeh , Batich Christopher , Heilbronner Edgar , Vogel Pierre , Carrupt Pierre‐Alain 
Published: September 2010

AbstractThe He(Iα) photoelectron spectra of 2,3,5,6‐tetramethylenebicyclo[2.2.1]heptane (1), 2,3,5,6‐tetramethylene‐7‐oxabicyclo[2.2.1]heptane (2), 2,3,5,6‐tetramethylenebicyclo[2.2.2]octane (3) and 5,6,7,8‐tetramethylenebicyclo[2.2.2]oct‐2‐ene (4) are presented. The assignments for the highest 4 or 5 π‐bands are made on the basis of LCBO and SPINDO calculations for compounds 1, 3 and 4. The results confirm the spectroscopic assignment of Klessinger et al. for the lower members of the series.Finally, the localized orbitals derived from SPINDO results, are used to discuss the “through‐bond” and “through‐space” interaction pattern in molecules 1, 3 and 4.
Synthetic applications of 2‐chlorotetrahydrofuran: Protection of alcohols as tetrahydro‐2‐furanyl (THF) ethers
Authors: Kruse C. G. , Jonkers F. L. , Dert V. , van der Gen A. 
Published: September 2010

Abstract2‐Chlorotetrahydrofuran (2‐Cl‐THF) is formed in 85% yield by reaction of sulfuryl chloride with excess THF. 2‐Cl‐THF reacts with alcohols, phenols, acids, thiols, azoles, amides and imides to give the corresponding tetrahydro‐2‐furanyl derivatives. Reaction with uracil derivatives provides N1‐ and N3‐monosubstituted and N1,N3‐disubstituted compounds. The reaction with alcohols provides a convenient general procedure for protecting the hydroxyl function. The THF group can be readily removed by acid catalyzed hydrolysis or reaction with methanol. The THF derivative of diphenylacetic acid can also be utilised for introducing the tetrahydro‐2‐furanyl moiety. THF ethers are converted into alkyl bromides by treatment with triphenylphosphine dibromide.
Vicinal carbon‐proton spin‐spin coupling constants in monosubstituted propanes
Authors: Spoormaker Tom , de Bie Marius J. A. 
Published: September 2010

AbstractAnalysis of single resonance 13C‐FT NMR spectra has yielded the vicinal 13C‐1H coupling constants in monosubstituted propanes for substituents from the first row of the Periodic Table. Directly bonded 13C‐1H, vicinal 1H‐1H and some directly bonded 13C‐13C coupling constants are also reported. The influence that the substituent electronegativity of the elements from the first row of the Periodic Table exerts on the vicinal 13C‐1H coupling constant is discussed qualitatively in terms of molecular orbital theory. The effects of substituents from the first row are compared with the effects of halogen substituents.
Stability constants of (hydroxy)carboxylate‐ and alditol‐calcium(II) complexes in aqueous medium as determined by a solubility method
Authors: Kieboom A. P. G. , Buurmans H. M. A. , van Leeuwen L. K. , van Benschop H. J. 
Published: September 2010

AbstractSolubility measurements of calcium(II) sulfate in aqueous solutions of (hydroxy)carboxylates and alditols have yielded apparent stability constants (M−1, at 25° and 0.2–0.8 M) for the complexes of calcium(II) with d‐gluconate (23), d‐lactate (17), acetate (7), and various alditols (0–1.4).
Preparation and properties of (dimethyldithiocarbamato)iodomethylarsenic(III) and its iodine complex; Crystal structure of MeAs(Me2NCS2)I2
Authors: Beurskens Gezina , Beurskens Paul T. , Noordik J. H. , Willemse J. , Cras J. A. 
Published: September 2010

AbstractThe preparation of an arsenic(III) dithiocarbamato iodo compound, MeAs(Me2dtc)I, and of its iodine complex, MeAs(Me2dtc)I2, is reported. The crystal structure of the iodine complex was determined by an X‐ray analysis. The monoclinic cell, space group P21/c, with a = 12.838(3), b = 8.374(1), c = 22.944(2) Å and β = 105.44(1)°, contains eight formula units. The two symmetry independent units are arranged in a nearly perfect C‐centred lattice. The phase problem was solved by the DIRDIF procedure (direct methods, including origin fixation, applied to difference structure factors). The atomic parameters were refined to a conventional R value of 0.07.The structure consists of I2IAsII2IAs chains, cross‐linked by IAsIAs chains to form two‐dimensional networks. The arsenic atoms are in quadrilaterally pyramidal coordination: As is slightly above the S,S,I,I‐plane; the methyl carbon forms the top of the pyramid. This methyl group breaks through the pseudo‐C‐centred translation symmetry.
A formalism for the classification and design of organic reactions III. The class of (+ ‐ )nC reactions
Authors: Arens J. F. 
Published: September 2010

AbstractThis paper deals with reactions involving an odd number of atoms. The bonds between the atoms alternatingly increase or decrease by one unit but one of the bonds remains unaffected. The reaction operator in terms of the formalism employed in the two previous papers thus is (+ ‐)nC in which C indicates the Constancy of the last mentioned bond.Many synthetically important processes belong to this class, among others acid‐ or base‐induced eliminations, ditto additions, isomerisations and substitutions, dipolar cycloadditions, fragmentations and tele‐reactions.