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Methyl Derivative (methyl + derivative)
Selected AbstractsBis(trimethylsilyl)methyl Derivatives of Calcium, Strontium and Barium: Potentially Useful Dialkyls of the Heavy Alkaline Earth ElementsCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2008Getting a complex! Dialkyls of the heavier Group,2 elements Ca, Sr and Ba (see figure) are simple to synthesise with careful selection of the correct alkyl ligand and reaction conditions. The crystal structures of three bis(trimethylsilyl)methyl complexes are reported, and contain the first unsupported Sr- and Ba-to-alkyl carbon bonds. [source] Asymmetric Synthesis of ,-Fluorinated ,-Amino Acid DerivativesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2005Deepak M. Shendage Abstract Asymmetric alkylation of (S)-Boc-BMI (1a, BMI = 2- tert -butyl-3-methylimidazolidin-4-one) and its ,-methyl derivative 1b with 2-fluoroallyl tosylate, subsequent mild acidic deprotection of the products 2a and 2b, and basic hydrolysis of the thus formed N -methylamides 4a and 4b gave (S)-2-amino-4-fluoropent-4-enoic acid (5a) and (S)-2-amino-4-fluoro-2-methylpent-4-enoic acid (5b). Basic hydrolysis of compound 4a was accompanied by partial racemization, which was overcome by applying a new stereoconservative deamidation procedure. The alkylated cis -configured product 2a formed under kinetic control epimerized on refluxing with 2 n NaOH to give the thermodynamically more stable trans isomer 9. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] 2,3,6,7,10,11-Hexamethoxytribenzotriquinacene: Synthesis, Solid-State Structure, and Functionalization of a Rigid Analogue of CyclotriveratryleneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 11 2004Marco Harig Abstract The syntheses of several tribenzotriquinacenes bearing six methoxy groups at the outer peripheral positions of the aromatic rings are reported. The centro -methyl derivative is accessible in surprisingly good yield through two-fold cyclodehydration in the final step of a synthesis route which requires special care in the preparation of some electron-rich key intermediates, such as 5,6-dimethoxy-2-methylindane-1,3-dione and bis(3,4-dimethoxyphenyl)methanol. X-ray single-crystal structure analysis of the centro -methyl derivative confirms its C3v -symmetrical molecular structure but, at variance from the parent centro -methyltribenzotriquinacene and the similarly shaped cyclotriveratrylene, the hexamethoxytribenzotriquinacene analog does not form columnar stacks in the solid state. Functionalization of the three benzhydrylic bridgehead positions leads to the tetramethyl analog and the bridgehead triol in good yields. In contrast, attempts to functionalize the ortho positions by nitration or bromination mainly give rise to ring cleavage through electrophilic ipso attack, which parallels the behavior of cyclotribenzylenes and cyclotriveratrylenes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and biological evaluation of carbon-11-labeled acyclic and furo[2,3-d]pyrimidine derivatives of bicyclic nucleoside analogues (BCNAs) for structure,brain uptake relationship study of BCNA tracersJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 3 2008Satish K. Chitneni Abstract We reported earlier on radiolabeled alkoxyphenyl bicyclic nucleoside analogues (BCNAs) as potential positron emission tomography (PET) reporter probes for imaging of varicella zoster virus thymidine kinase (VZV-tk) gene in vivo. Despite their favorable physicochemical properties, these tracers are not taken up in the brain in mice. In order to probe the role of the deoxyribose sugar moiety in blood-brain barrier (BBB) penetration of these molecules, we have synthesized and evaluated a carbon-11-labeled acyclic bicyclic nucleoside derivative ([11C]-10) where the 2,-deoxyribose sugar is replaced with a (2-hydroxyethoxy)methyl group and [11C]-12, which has no sugar moiety but a [11C]methyl group on the N-3 position of the pyrimidine ring. Methylation was achieved on the phenol ([11C]-10) or the N-3 position ([11C]-12) using [11C]methyl triflate (radiosynthesis). The (non-radioactive) acyclic O -methyl derivative 10 has rather poor affinity for the enzyme VZV-TK in vitro (IC50: 430,µM), compared with the moderate affinity of the BCNA-base N -methyl derivative 12 (IC50: 79,µM). In normal mice, none of the two tracers ([11C]-10 or [11C]-12) showed significant uptake in the brain, suggesting that compounds containing a furo[2,3- d]pyrimidine system do not cross the BBB. Copyright © 2008 John Wiley & Sons, Ltd. [source] The Hammett equation applied to the nucleophilic displacement of ions and ion pairs on substituted benzenesulphonatesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2001Sergio Alunni Abstract Nucleophilic substitution on meta - and para -substituted methyl benzenesulphonates was studied with two chloride salts with different structures: NBu4Cl or KCl-Kryptofix 2,2,2. Treating the results with the Acree equation shows that the reaction proceeds by two reaction paths, one involving the chloride ion and the other, slower one, involving the ion pairs. Treating the results with the Hammett equation gives consistent data, and shows that , is positive and nearly the same for the two reaction paths (,,,,+2). The reactivity of methyl p -nitrobenzenesulphonate was compared with that of the corresponding ethyl derivative, and it is shown that the methyl derivative reacts faster than the ethyl derivative in both paths. The results are interpreted based on the assumption that in both paths a negative charge is developed on the leaving group in the transition state, and that the activated complex is linear. Copyright © 2001 John Wiley and Sons, Ltd. [source] C,H···X (X = N, O, S) intramolecular interaction in 1-vinyl-2-(2,-heteroaryl)pyrroles as monitored by 1H and 13C NMR spectroscopyMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2002Andrei V. Afonin Abstract 1H and 13C NMR spectroscopy of a series of 1-vinyl-2-(2,-heteroaryl)-pyrroles were employed for the analysis of their electronic and spatial structure. The C,H···N intramolecular interaction between the ,-hydrogen of the vinyl group and the pyridine nitrogen, a kind of hydrogen bonding, was detected in 1-vinyl-2-(2,-pyridyl)pyrrole, which disappeared in its iodide methyl derivative. It was shown that this interaction is stronger than the C,H···O and C,H···S interactions in 1-vinyl-2-(2,-furyl)- and -2-(2,-thienyl)-pyrroles. Copyright © 2001 John Wiley & Sons, Ltd. [source] 4-(9,10-Dihydroacridin-9-ylidene)thiosemicarbazide and its five-membered thiazole and six-membered thiazine derivativesACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010Ivan Poto Two methyl derivatives, five-membered methyl 2-{2-[2-(9,10-dihydroacridin-9-ylidene)-1-methylhydrazinyl]-4-oxo-4,5-dihydro-1,3-thiazol-5-ylidene}acetate, C20H16N4O3S, (I), and six-membered 2-[2-(9,10-dihydroacridin-9-ylidene)-1-methylhydrazinyl]-4H -1,3-thiazin-4-one, C18H14N4OS, (II), were prepared by the reaction of the N -methyl derivative of 4-(9,10-dihydroacridin-9-ylidene)thiosemicarbazide, C14H12N4S, (III), with dimethyl acetylenedicarboxylate and methyl propiolate, respectively. The crystal structures of (I), (II) and (III) are molecular and can be considered in two parts: (i) the nearly planar acridine moiety and (ii) the singular heterocyclic ring portion [thiazolidine for (I) and thiazine for (II)] including the linking amine and imine N atoms and the methyl C atom, or the full side chain in the case of (III). The structures of (I) and (II) are stabilized by N,H...O hydrogen bonds and different ,,, interactions between acridine moieties and thiazolidine and thiazine rings, respectively. [source] 3-Amino-4,-methyl-5-ethylbiphenyl-2,4-dicarbonitrile and 3-amino-4,-(N,N -diethylamino)-5-ethylbiphenyl-2,4-dicarbonitrileACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2001A. Subbiah Pandi In the title compounds, C17H15N3 and C20H22N4, the methyl derivative crystallizes with two molecules in the asymmetric unit, while the N,N -diethylamino derivative crystallizes with one molecule per asymmetric unit. The biphenyl twist angle for both molecular structures is approximately 45°. The molecular packing is stabilized by N,H,N hydrogen bonds. [source] Stereoselective Hydrolysis of Quaternary Quinuclidinium Benzoates Catalyzed by ButyrylcholinesteraseEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2003Ines Primoz Abstract Four chiral, quaternary, N -methyl and N -benzyl derivatives of (R)- and (S)-quinuclidin-3-yl benzoates were synthesized and studied as substrates of horse serum butyrylcholinesterase (BChE). The kcat for the substrates decreased in the order (R)- N -methyl > (R)- N -benzyl (2.3-fold slower) >> (S)- N -methyl (70.5-fold slower reaction), while for the (S)- N -benzyl ester inhibition of the enzyme was observed. The kinetics of inhibition (Ka = 3.3 ,M) indicated that binding to the catalytic site of BChE occurred. From the ratio of the kcat/KM values of both enantiomers an enantiomeric excess of 95% was calculated for N -methyl derivatives. Thus, BChE is suitable as a biocatalyst for the resolution of racemic quaternary quinuclidinium esters. In order to explain the experimental data, combined quantum chemical (HF/3,21G*) and semiempirical (PM3) calculations within the ONIOM scheme of the stable species in the acylation step were performed. Geometry optimizations were carried out for all benzoate esters for an assumed active site model of BChE. It was confirmed that hydrolysis is affected to an appreciable extent by a proper geometrical orientation of substrates at the choline subsite. The energies of the optimized systems were in good agreement with the experimental data. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Synthesis, characterization and biological activity of some 1,2,4-triazine derivativesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2005A. A. El-Barbary 4-Amino-6-methyl-3-(2H)-thioxo-5-(4H)-oxo-1,2,4-triazine (1) was condensed with 2-methyl (or phenyl)-4H -3,1-benzoxazin-4-one (5a,b) in boiling acetic acid to give compounds 8-11. Reacting 1 with chloroacetyl chloride afforded the corresponding chloroacetamido and triazinothiadiazine derivatives 12 and 13. Condensing 2 with succinic anhydride and/or phthalic anhydride yielded compounds 14 and 15. Benzoylation of 4-amino-6-methyl-3-(2H)-thioxo-5-(4H)-oxo-2-(2,3,4,5-tetra- O -acetyl-,-D-glucopyra-nosyl)-1,2,4-triazine (19) afforded the corresponding 4- N,N -dibenzoyl derivative 20. Deblocking of the N -2 glycoside 21 and the S -glycoside 22 by methanolic ammonia gave compounds 23 and 24. Acetylation of 4-amino glycoside 25a afforded the corresponding 4-mono- and 4-diacetyl derivatives 26 and 27. Deamination of 25a,b yielded compounds 28a,b. Methylation of compound 28b afforded the corresponding N4- and S -methyl derivatives 29 and 30. [source] 1,6- and 1,7-naphthyridines III.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 200213C-NMR analysis of some hydroxy derivatives The 13C-NMR spectra of some 1,6-naphthyridines 2 and 1,7-naphthyridines 3, as well as those of N -methyl derivatives 4 and 5, were recorded and analyzed. Results in dimethyl- d6 sulfoxide and deuteriochlo-roform provide useful data on intra and intermolecular hydrogen bonds. [source] Temperature and solvent dependent NMR studies on mangiferin and complete NMR spectral assignments of its acyl and methyl derivativesMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2006Shaheen Faizi Abstract By employing concerted 1 and 2D NMR techniques, exact NMR spectral assignments have been made of the acyl (2,7) and methyl (8 and 9) derivatives of mangiferin (1) isolated from the leaves of Bombax ceiba. Derivatives 2, 8 and 9 have been reported in literature, while 3,7 represent new compounds. The acetates 2 and 3 were found to be unstable and were converted into the same penta-acetate 4 at room temperature. Extensive NMR studies on mangiferin (1) and its derivatives showed that H-4 exchanges with deuterium of the solvent molecule more easily. This exchange under acidic conditions occurred at that position (C-4) where electrophilic substitution reactions can easily take place. This is the first report describing the exchange of C-4 proton of mangiferin (1), or any other xanthone, with deuterium of solvent molecules. Copyright © 2006 John Wiley & Sons, Ltd. [source] 4-(9,10-Dihydroacridin-9-ylidene)thiosemicarbazide and its five-membered thiazole and six-membered thiazine derivativesACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010Ivan Poto Two methyl derivatives, five-membered methyl 2-{2-[2-(9,10-dihydroacridin-9-ylidene)-1-methylhydrazinyl]-4-oxo-4,5-dihydro-1,3-thiazol-5-ylidene}acetate, C20H16N4O3S, (I), and six-membered 2-[2-(9,10-dihydroacridin-9-ylidene)-1-methylhydrazinyl]-4H -1,3-thiazin-4-one, C18H14N4OS, (II), were prepared by the reaction of the N -methyl derivative of 4-(9,10-dihydroacridin-9-ylidene)thiosemicarbazide, C14H12N4S, (III), with dimethyl acetylenedicarboxylate and methyl propiolate, respectively. The crystal structures of (I), (II) and (III) are molecular and can be considered in two parts: (i) the nearly planar acridine moiety and (ii) the singular heterocyclic ring portion [thiazolidine for (I) and thiazine for (II)] including the linking amine and imine N atoms and the methyl C atom, or the full side chain in the case of (III). The structures of (I) and (II) are stabilized by N,H...O hydrogen bonds and different ,,, interactions between acridine moieties and thiazolidine and thiazine rings, respectively. [source] HPLC determination of acidic d -amino acids and their N -methyl derivatives in biological tissuesBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Mara Tsesarskaia Abstract d -Aspartate (d -Asp) and N -methyl- d -aspartate (NMDA) occur in the neuroendocrine systems of vertebrates and invertebrates, where they play a role in hormone release and synthesis, neurotransmission, and memory and learning. N -methyl- d -glutamate (NMDG) has also been detected in marine bivalves. Several methods have been used to detect these amino acids, but they require pretreatment of tissue samples with o -phthaldialdehyde (OPA) to remove primary amino acids that interfere with the detection of NMDA and NMDG. We report here a one-step derivatization procedure with the chiral reagent N-, -(5-fluoro-2,4-dinitrophenyl)-(d or l)-valine amide, FDNP-Val-NH2, a close analog of Marfey's reagent but with better resolution and higher molar absorptivity. The diastereomers formed were separated by HPLC on an ODS-Hypersil column eluted with TFA/water,TFA/MeCN. UV absorption at 340 nm permitted detection levels as low as 5,10 pmol. d -Asp, NMDA and NMDG peaks were not obscured by other primary or secondary amino acids; hence pretreatment of tissues with OPA was not required. This method is highly reliable and fast (less than 40 min HPLC run). Using this method, we detected d -Asp, NMDA and NMDG in several biological tissues (octopus brain, optical lobe and bucchal mass; foot and mantle of the mollusk Scapharca broughtonii), confirming the results of other researchers. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||