Search results for "ALK"
showing 10 items of 4314 documents
One-Pot Three-Component Solvent-Free Syntheses of n-Alkyl-Bridged N,N,N,N-tetra(2-hydroxybenzyl)diamines and N,N-bis(2-hydroxybenzyl) amines
2010
A simple solvent-free method to prepare four N,N,N’,N’-tetra(2-hydroxy-3,5dimethylbenzyl)diaminoalkanes and four N,N,N’,N’-tetra(2-hydroxy-5-t-butyl-3-methylbenzyl)-diaminoalkanes containing a long n-alkyl-bridge (58 CH2 groups between N-atoms) is described. In addition, preparations of four dihydrochlorides of prepared n-alkyl-bridged N,N,N’,N’-tetra(2-hydroxybenzyl)diamines are described. This method was also tested in the preparation of eight previously reported N,N-bis(2-hydroxybenzyl)amine derivatives.
On the determination of underivatised fatty alcohol ethoxylates by electrospray ionisation–mass spectrometry
2006
Abstract The oligomers of fatty alcohol ethoxylates (FAEs) exhibit large sensitivity differences in mass spectrometry with electrospray ionisation (ESI–MS) and atmospheric pressure chemical ionization (APCI). Standards of the oligomers from m = 1 to 7 ethylene oxide units (EOs) and linear alkyl chains from n = 10 to 18 carbon atoms were infused to examine the relative sensitivities or response factors in several media. The response factors of the [M + H]+ and [M + Na]+ peaks in 9:1 acetonitrile/water and methanol/water media containing acid buffers increased following irregular patterns when n and m increased. In methanol/water the response factors depended on the parity of m, being larger …
d-Glucose as a multivalent chiral scaffold for combinatorial chemistry
2002
Due to their high density of functional groups and their availability in a variety of diastereomeric forms, monosaccharides are considered attractive scaffolds for combinatorial chemistry that allow the attachment and defined spatial alignment of up to five different pharmacophoric groups. For their application in combinatorial syntheses on solid phase, a set of selectively removable hydroxy protecting groups in combination with a cleavable anchor is required. Herein, we report on the construction and use of a versatile multivalent glucose building block for parallel synthesis on the solid phase.
Partialsynthese neuer Ergolinderivate aus Clavinalkoloiden, 5. Mitt. N-1- und N-6-mono- und disubstituierte Festuclavine
1985
Festuclavin (1), 6-Cyano-6-nor-1 (3), 6-Nor-1 (5) und 6-Allyl-6-nor-1 (7) lassen sich in flussigem Ammoniak mit Kalium und dem entsprechenden Iodid in ihre 1-Allyl- und 1-Propyl-Derivate uberfuhren. Die Darstellung von 7 aus 5 wird beschrieben. Partial Syntheses of New Ergoline Derivatives from Clavine Alkaloids, V: Festuclavines Mono- and Disubstituted at N-1 and N-6 Festuclavine (1), 6-cyano-6-nor-1 (3), 6-nor-1 (5) and 6-allyl-6-nor-1 (7) were converted to their 1-allyl- and 1-propyl derivatives with potassium and the corresponding iodide in ammonia. The preparation of 7 from 5 is described.
Stereoselective synthesis of 7,11-guaien-8,12-olides from santonin. Synthesis of podoandin and (+)-zedolactone A.
2000
Photochemical rearrangement of hydroxy ester 2, easily obtained from santonin (1), afforded butenolide 4, a good starting material for the synthesis of 7,11-guaien-8,12-olides. Compound 4 has been transformed into compound 10, which has been used for the synthesis of podoandin (5) and (+)-zedolactone A (ent-6). Regioselective elimination of the acetyl group on C10 afforded directly podoandin (5). For the synthesis of ent-6, a hydroxyl group has been regio- and stereoselectively introduced at the 4alpha-position through the 3alpha,4alpha-epoxide 15. The basic hydrolysis of the 10-acetyl group in compound 18 took place with concomitant intramolecular conjugated addition of the alkoxide to the…
Studien zum Vorgang der Wasserstoffübertragung, 53. Beitrag zur Kenntnis der elektroreduktiven Spaltung von Hydroxylaminderivaten
1978
Die Elektroreduktion von 26 Hydroxylaminderivaten wird polarographisch und an 6 Beispielen praparativ untersucht. Es wurde gefunden: 1) Dreifach mit Alkyl- oder Arylgruppen substituierte Hydroxylaminderivate werden bis zu einem Potential von -2.5 V (gegen Ag/AgCl/KClges.) nicht elektroreduziert. — 2) Der Einbau von Acylgruppen erleichtert in Abhangigkeit von Art, Zahl und Verknupfungsstelle die Elektroreduktion. Acylreste mit aromatischen Gruppen verschieben das Halbstufenpotential starker nach positiven Werten als aliphatisch substituierte Acylreste (entsprechend: Phthaloyl > Benzoyl > Formyl > Acetyl > Ethoxycarbonyl). Acylgruppen am Sauerstoff des Hydroxylamins fordern die Elektroredukti…
Alkyl and Aryl Substituted Corroles. 2. Synthesis and Characterization of Linked “Face-to-Face” Biscorroles. X-ray Structure of (BCA)Co2(py)3, Where …
2001
The synthesis, spectroscopic properties, and electrochemistry of (BCA)Co(2) and (BCB)Co(2) are described where BCA and BCB represent biscorroles linked by an anthracenyl (A) or a biphenylenyl (B) bridge. The pyridine and CO binding properties of (BCA)Co(2) and (BCB)Co(2) are also presented, and one of the compounds in its pyridine-ligated form, (BCA)Co(2)(py)(3), is structurally characterized. The data on the biscorroles are compared on one hand to the monocorrole having the same substitution pattern and on the other hand to bisporphyrins having two Co(II) ions and the same anthracenyl or biphenylenyl linkers in order to better understand the interaction which occurs between the two corrole…
Racemic and Optically Pure Heptahelicene-2-carboxylic Acid: Its Synthesis and Self-Assembly into Nanowire-Like Aggregates
2010
Heptahelicene-2-carboxylic acid was effectively synthesised from suitably functionalised naphthalene building blocks. Methoxy-substituted 1,1'-ethyne-1,2-diylbis(2-but-3-yn-1-ylnaphthalene) was cyclised in the presence of CpCo(CO)(2)/PPh(3) to 2-methoxy-7,8,11,12-tetrahydroheptahelicene, which was converted into heptahelicen-2-yl trifluoromethanesulfonate. This reactive intermediate underwent Pd(OAc)(2)/dppp-catalysed methoxycarbonylation reaction to provide, after hydrolysis, heptahelicene-2-carboxylic acid. The racemate was resolved into enantiomers by semipreparative HPLC on a chiral column. The helicity of (+)-(P)-heptahelicene-2-carboxylic acid was assigned by correlating its CD spectr…
Discrete bond model (DBM) of sodium silicate glasses derived from XPS, Raman and NMR measurements
1993
In sodium silicate glasses, the fraction of differently bound Si species Q[i] (i = 0−4), depending on the number i of bridging oxygens bound to the quarternary silicon, is a function of stoichiometry and the Na/Si ratio. Sodium silicate glasses were investigated by high resolution X-ray photoelectron spectroscopy. To explain the differences in chemical shifts and linewidths of the O 1s signal of the bridging and the non-bridging oxygen as a function of alkali concentration, and extended glass model was developed. This new model takes into account the influence of the alkali concentration on the Q[i] distribution and on the appearance and concentrations of differently bound bridging oxygens …
Über tetraaryl-methan-analoga in der gruppe 14
1994
Abstract The title compounds have been synthesized by Grignard reactions or pyrolysis of diplumbanes respectively. The crystal structures of m -Tol 4 Pb and Ph 4 Pb (redetermination) have been determined. All eight compounds (Ph/Tol) 4 (Sn/Pb) are S 4 symmetric and contracted along this unique axis. The 13 C-NMR chemical shifts and the couplings 1 J ( 119 Sn/ 207 Pb 13 C) as well depend additively upon the methyl substituents. The ratios 1 K ( 207 Pb 13 C): 1 K ( 119 Sn 13 C) of the reduced coupling constants are all near to 1.61; a comparison with values from the literature for alkyl, alkenyl and alkinyl substituents is given. The ratio δ( 207 Pb):δ( 119 Sn) results in 2.28. IR (700 dow…