Derives 14-hydroxyles de la vincadifformine et de la vincamine

Hydroboration-oxidation of tabersonine 1 yielded as major product 14 β-hydroxy vincadifformine 9b, which was correlated with 14 β-hydroxy N(1)-methyl 2β-H, 16β-H dihydro vincadifformine 6b (previously prepared and characterised), and 14α-hydroxy vincadifformine 9a as minor product. The regio- and stereoselectivity of hydroboration-oxidation were interpreted. 9a and 9b were respectively oxidised and rearranged to the corresponding 14-hydroxy vincamines 13a and 13b. The coupling constants of H(14) on the NMR of the acetyl derivatives of 9a, 9b, 13a and 13b are consistent with an inversion of N(4) during the rearrangement leading from the vincadifformine to the vincamine skeleton.     

Radiosensibilisation de la thymine en presence de tetramethyl-2,2,6,6 piperidone-4 oxyle-1. caracterisation des produits d'addition

The reaction of 2,2,6,6-tetramethyl-4-piperidone-1-oxyl with radiation-formed 5,6-dihydro-6-hydroxy-thymin-5-yl and 5,6-dihydro-5-hydroxy-thymin-6-yl radicals in oxygen-free aqueous solution generate respectively two major products 2 and 3. The chemical assignment of both covalent addition derivatives is based mainly on ¹³C NMR and mass spectrometry (chemical ionization and field desorption) analysis. The N-oxide 2, which was prepared in a specific manner, undergoes Cope elimination and radical rearrangement within the pyrimidine ring.     

Dosage direct de submicrotraces de bore dans la soude de purete analytique par la methode fluorimetrique a l'hydroxy-2-methoxy-4-chloro-4'-benzophenone

A method based on the highly sensitive fluorescent reaction of boric acid with 2-hydroxy-4-methoxy-4'-chlorobenzophenone (H.M.C.B.), is described for the direct determination of traces of boron in “analytical grade” sodium hydroxide. In the nanogram range, the reliability of the H.M.C.B. method is satisfactory; the fluorescent reaction is not affected by up to 8% (v/v) of water. The sample is dissolved directly in concentrated sulfuric acid and no preliminary separation is needed. Interferences from other impurities of sodium hydroxide are negligible. Results for five different “analytical grade” reagents were: (0.9±0.2)·10^-6,(3.2±0.3)·l0^-6,(3.2±0.3)·^-6, (4.0±0.4)·10^-6and(2.0±0.16)·10^-6% B.     

Synthese de derives de la purpurosamine C,composant de la gentamicine C1a

The synthesis of derivatives of purpurosaimine C and epi-purpurosamine C is described, from methyl 2,3,4,6-tetra-O?-methylsulphonyl-α-d-galacto and glucopyranosides 2 and 3 by reaction with azide ion to give diazides 4 and 5, transformed in a series of reactions via epoxides 6 and 7 into the corresponding olefines 16 and 17, thermal rearrangement to give diazides 18 and 19, which were transformed into the methyl glycosides 27 and 29 and mercaptolysis with ethanethiol followed by N-acetylation, gave 2,6-diacetamido-2,3,4,6-tetradeoxy-d-erythro-hexose diethyl dithioacetal 30 (identical with authentic 30 prepared from gentamicin C_1a)and 2,6-diacetamido-2,3,4,6-tetradeoxy-d- threo-hexose diethyl dithioacetal 31, an enantiomer of a mercaptolysis product of dihydrosisomicin.     

Rearrangement thermique des adduits du tetracyanoethylene de 2H-pyrannes

The addition of tetracyanotehylene to 2H-pyrans 1 results in a mixture of two isomeric adducts 6. The thermal decomposition of the compounds 6 gives rise to both a small percentage of the retro Diels-Alder, and a new mode of evolution leading to a mixture of furans (E+Z) 7. A detailed interpretation of the ¹³C spectra of the compounds 7 was established by comparison with the ¹³C spectra of 2,5-diphenylfuran and trans-stilbene. The structure 7 is confirmed by chemical degradation.     

Syntheses totales et etudes de lignanes biologiquement actifs—I : Application de la reaction d'ullmann a la synthese de biaryles precurseurs de lignanes bisbenzocyclooctadienes

Several biaryls bearing various substituents on both rings were synthesized in a preparative fashion, and in yields up to 88% by a technical improvement on the classical Ullmann reaction. All these biaryls bear reactive functional groups (i.e. formyl, methoxycarbonyl, dimethoxycarbonylpropyl and butanolidylmethyl) in both the o and o′ positions. The biaryls 9, 13, 21 and 26–33 are plausible synthons for bisbenzocyclooctadiene lignans such as schizandrin and steganacin.     

Synthese de derives de la tobrosamine par addition d'acide hydrazoique sur un systeme enonique dans la serie hydrate de carbone

Derivatives of a new diaminotrideoxy-d-ribo-hexopyranose, a component of the antibiotic tobramycin, have been prepared by addition of the elements of hydrazoic acid to the α, β-unsaturated ketone 8. After 5 min only the kinetically favored product 13 was observed, which is gradually transformed into the thermodynamically more-stable substance 20. The equilibrium mixture after 5 hours contained d-erythro and d-threo isomers 20 and 13 in the ratio 6:4 The d-erythro azide 20 was converted into the derivatives of di-N-acetyl tobrosamine.     

Contribution a la valorisation industrielle des dechets de tanneries: cas de la cimenterie

A contribution to the industrial valorization of tannery waste: the case of cement industry. The present work addresses the possibility of valorization of tannery waste incineration ashes in the cement industry. To this end, the impact of the addition of ashes at various percentages (0, 5, 10, 15, 20, 25, 30, 35, 40, and 45 % in mass) on some mechanical and physical parameters of cement was examined: normal consistency (%), the beginning of setting (hr), the end of setting (hr), the hot expansion (mm), the resistances to compression and to bending (N/mm²) determined on normalized 4x4x16 cm samples. The impact of the treatment environment (20 °C and 100% of relative humidity RH, 30 °C and 70 % RH, 45 °C and 45% RH) was also taken into consideration. The obtained results reveal that the normal consistency, the beginning and the end of setting vary linearly with the quality of added ashes. Above an addition of ashes of 30 %, the end of setting exceeds the standards demanding a maximum of 10 hours. Additionally, the results indicate that whatever the environment treatment may be, the resistances to compression and to bending increase with the increase of the sample age; they vary inversely to the amount of ash addition. The results allow to conclude that for an ash addition of 15 % and after an ageing of 30 days, the resistance to compression is higher than 40 N/mm², thus allowing the production of CPA 400 cement. These results also allow to conclude that samples kept in a humid environment give the best resistances to compression and to bending, by comparison with those kept in a dry environment.     

Polybrominated oxydiphenol derivatives from the sponge dysidea herbacea: Structure determination by analysis of 13C spin-lattice relaxation data for quaternary carbons and 13C-1H coupling constants

Five polybrominated oxydiphenol derivatives have been isolated from various Great Barrier Reef collections and one Fijian collection of the sponge Dysidea herbacea: 3,4',5,6,6'-hexabromo-2, 2'-oxydiphenol (11), 3,4',5,6,6'-pentabromo-2,2'-oxydiphenol (12), 3.4',5,6,6'-pentabromo-2,2'-oxydiphenol 1-methyl ether (13), 3,4,4',5,6'-pentabromo-2,2'-oxydiphenol 1,1'-dimethyl ether (14) and 3,4',5,6'-tetrabromo-2,2'-oxydiphenol 1'-methyl ether (15).The structure of the first member of this series is determined by a new method involving ¹³C spin-lattice relaxation data. The contributions of nearby hydrogens to quaternary carbon spin-lattice relaxation times are calculated for various possible structures and compared with the experimental data, leading to an unequivocal proof of structure. The structures of the remaining compounds in the series are established principally by analysis of ¹³C chemical shifts and ¹³C-¹H coupling constants.     

Photocycloaddition des hydrocarbures aromatiques polynucleaires en solution—iv: Etude de la fluorescence et de la photoreactivite de l'acenaphtylene et du cyano-1 acenaphtylene

The fluorescence of acenaphthylene follows a Stern-Volmer relationship in air-saturated ether giving a self-quenching constant K_F=0.12M^?1, indicating that the syn photodimer originates from the singlet state of acenaphthylene. By comparison, 1-cyanoacenaphthylene undergoes a more efficient self-quenching (K_F= 2.8 M^?1) in air-saturated ether. No excimer fluorescence was detected for 1-cyanoacenaphthylene nor the parent compound in solution. The triplet state of 1-cyanoacenaphthylene, obtained by sensitization or induced by heavy atom solvent (EtI), was shown to generate exclusively the head-to-head anti photodimer in a high chemical yield. Regiospecificity and stereospecificity observed in this reaction indicates the influence of the acenaphthylenic ring and the cyano group in stabilizing the diradicaloïd transition state.     

Etude de la reaction chlorocarbene-acetals de cetenes : II. Stereoselectivite de la reaction

We have studied the stereoselectivity of the addition reaction of chloro and chloromethyl carbenoids with ketene alkylsilyl acetals. The best stereoselectivity was generally observed with the dimethyl tertiobutylsilyloxy group. With the chlorocarbenoid, using an E ketene acetal we obtained in majority (8?0%) an E α,β-ethylenic ester and using a Z ketene acetal we obtained in majority (7?0%) a Z α,β-ethylenic ester. In the case of the chloromethyl carbenoid the two ketene acetal isomers led to the same E α-substituted α,β-ethylenic ester (8?8% of selectivity). With the chlorophenylcarbenoid, formation of 9?0% of E α phenyl α,β-ethylenic ester is observed.     

Etude par rmn de31p de la reaction de l'hexamethylphosphotriamide avec le trichlorure de phosphoryle

The reaction of HMPT with POCl₃ was studied by ³¹P NMR at various temperatures and stoechiometries. Progressive substitution of chlorine atoms of phosphoryl chloride by HMPT molecules was observed. Six new species were involved in the system. The main produce was the $\text{1}\text{1}$ adduct, (Me₂N)₃P⁺Cl, O₂PCl₂^?, analogous to Vilsmeier complex.     

Structures de modeles de polyesters—I. Separation et etude par RMN [13C]des dihydroxy-2,3 butane, 2,4 pentane et 2,5 hexane et de leurs benzoates

[¹³C]NMR spectra have been obtained for a series of diols and benzoates, models of 2,3-dihydroxybutane, 2,4-dihydroxypentane and 2,5 dihydroxyhexane terephthalates after separation of diastereoisomers by gas and liquid-liquid chromatography. Chemical shifts for the meso and racemic derivatives have been interpreted in terms of rotational isomers. The results indicate that [¹³C]NMR is more sensitive than [¹H]NMR for the differentiation of diastereoisomers. Carbonyl and aromatic quaternary carbon chemical shifts are sensitive to the stereochemistry of the chain (long range effects) but relaxation times and nuclear Overhauser enhancements are identical in the two diastereoisomers.     

Electrophilic reactions of chlorin derivatives and a comprehensive collection of 13c data of these products and closely related compounds

Vilsmeier-formylation of the copper(II) complex of chlorin-e₆ trimethyl ester (2), under mild conditions, gives selective substitution in the 3-vinyl group. In contrast chlorination of 2 is shown to lead to selective substitution at position 20 of the macrocycle. A similar result is found for [3-ethyl]-isochlorin-e₄ dimethyl ester (17) although further reaction leads to more highly chlorinated products which have been isolated and identified. ¹³C NMR data for some of these compounds and several related chlorin derivatives are reported. In particular, after correction of the literature, many of the quaternary carbon signals of the macrocycle are assigned and substituent effects assessed. Consideration of the shifts of the α-pyrrolic carbons confirms that chlorin and its derivatives exist in a tautomeric form with the two inner H atoms on diagonally opposite pyrrole rings A and C. Such a form allows a satisfactory explanation of the substituent chemical shifts of the formyl group at positions 15 and 20 to be made.     

Étude de la vindolinine—III: Hémisynthèse de l'andranginine

Thermolysis of Δ¹⁸-tabersonine 3 in methanol solution affords, (±)andranginine 5, (±) épi-andranginine 9a and optically active 6.     

The first enantiospecific total synthesis of a C-quaternary voachalotine alkaloid, (+)-dehydrovoachalotine

The first enantiospecific total synthesis of the indole alkaloid (+)-dehydrovoachalotine (1) has been achieved from d-(+)-tryptophan methyl ester in 28% overall yield. The formation of the prochiral quaternary carbon center at C-16 in the key intermediate (12) was realized via a Tollens reaction from N_a-methylvellosimine (13) in 95% yield. This approach could also be applied to the synthesis of many other indole alkaloids that contain a quaternary carbon center at C(16).     

Interaction entre groupes aromatique et polaire voisins—III: Synthese et etudes physico-chimiques d'acides p-x-phenyl-3 bicyclo[2.2.1] heptene-5 carboxyliques-2 et de leurs esters methyliques

The synthesis, ¹H and ¹³C NMR spectra of acids 1 to 4 and methyl esters 5 to 8 are described. Interaction of aromatic and polar groups in the cis acids must be steric in origin and not due to charge transfer complex or hydrogen bonding. The structure of 1e,3a,5e and 7e has been determined by X-Ray crystallography. ¹H and ¹³C NMR studies indicate that, in the cis compounds, the proximity of aromatic and polar groups tend to impose to them some largely predominant conformations which should be analogous in the crystal or in solution.     

Phosphatriptycene

Phosphatriptycene (1) is prepared by cyclizing 9-(o-chlorophenyl)-9,10-dihydrophosphaanthracene (6) with an excess of lithium diisopropylamide in ether. Its structure is confirmed by its ¹³C-NMR spectrum. In nucleophilic reactions 1 is less reactive than triphenylphosphine. The nature of the bonding in quaternary phosphonium salts of 1 is discussed.     

Recherches sur la synthese totale des alcaloides appartenant a la serie de la carpaine et de la cassine—III : Deux methodes generales de synthese des ethylenedioxy-4,4 aldehydes

4,4-ethylenedioxy aldehydes 1 can be obtained readily from 1-ethoxycarbonyl 6-methyl hept-5-en 2-one 8 by C-alkylation, followed by hydrolysis, decarboxylation, dioxolane formation and ozonolysis. Alternatively, compounds 1 can be prepared by reacting the Grignard reagent of 1-bromo 4-methyl pent-3-ene 24 with an appropriate aldehyde, followed by oxidation, dioxolane formation and ozonolysis. Compounds of type 1 should prove useful in the total synthesis of carpaine, cassine and related alkaloids.     

Equation de Karplus et l'Hybridation du Carbone. Correlation de la Constante de Couplage Vicinale 3J(Hi,Hj) et la Somme de Constantes de Couplages 1J(C,H)

The vicinal coupling constant ¹H? ¹H exhibits a marked hybridization dependence. The coupling constants ¹³C? ¹H could be used to correlate the Karplus type equation for calculation of ³J(Hi, Hj). The correction term to this equation is proposed.