- A facile microwave assisted synthesis and structure elucidation of (3R)-3-alkyl-4,1-benzoxazepine-2,5-diones by crystallographic, spectroscopic and DFT studies
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The use of microwave (MW) irradiation in organic synthesis has become increasingly popular within the pharmaceutical and academic arenas because it is a new enabling technology for drug discovery and development. It is a rapid way of synthesis, which involves faster reaction rates and high selectivity to conventional heating method of syntheses. The MW-assisted 7-exo-tet cyclization of N-acylanthranilic acids afforded (3R)-3-alkyl-4,1-benzoxazepines-2,5-diones in very short duration (20 min) with extraordinary high yields in comparison to conventional heating mode of synthesis. The method development, comparative yields of MW-assisted and thermal method of syntheses, crystallographic, spectroscopic and density functional theory (DFT) studies are reported herein. Four novel compounds with chemical formulas C10H9BrClNO3 5m, C19H19NO3 6e, C13H14ClNO3 6h and C12H11Br2NO3 6h were synthesized, validated by 1HNMR, 13CNMR, FT-IR, UVVis, EIMS spectroscopic techniques and confirmed by using single crystal X-ray diffraction (SC-XRD) study. The DFT and TDDFT calculations at B3LYP/6-311 + G(d,p) level of theory were performed for comparative analysis of spectroscopic data, optimized geometries, frontier molecular orbitals (FMOs), natural bond orbital (NBO) analysis and nonlinear optical (NLO) properties of 5m, 6e, 6h and 6o. Overall, experimental findings were supported nicely by corresponding DFT computed results. The NBO analysis confirmed that the presence of non-covalent interactions, hydrogen bonding and hyper- conjugative interactions are pivotal cause for the existence of 5m, 6e, 6h and 6o in the solid-state. NLO analysis showed that 5m, 6e, 6h and 6o have significant NLO properties as compared to prototype standard compound which disclosed their potential for technology related applications.
- Raza, Abdul Rauf,Nisar, Bushra,Khalid, Muhammad,Gondal, Humaira Yasmeen,Khan, Muhammad Usman,de Alcantara Morais, Sara Figueirêdo,Tahir, Muhammad Nawaz,Braga, Ataualpa Albert Carmo
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- Chiral Pool-Based Synthesis of Naphtho-Fused Isocoumarins
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A variety of chiral derivatives of benzo[d]naphtho[1,2-b]pyran-6-one were prepared in a single step by Et3N-mediated condensation of homophthalic anhydride with different derivatives of (S)-amino acid chlorides at -5 °C by employing a chiral pool methodology. Chirality 27:951-957, 2015.
- Raza, Abdul Rauf,Saddiqa, Aisha,?akmak, Osman
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p. 951 - 957
(2015/11/16)
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- Iron-Catalyzed Enantioselective Cross-Coupling Reactions of α-Chloroesters with Aryl Grignard Reagents
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The first iron-catalyzed enantioselective cross-coupling reaction between an organometallic compound and an organic electrophile is reported. Synthetically versatile racemic α-chloro- and α-bromoalkanoates were coupled with aryl Grignard reagents in the presence of catalytic amounts of an iron salt and a chiral bisphosphine ligand, giving the products in high yields with acceptable and synthetically useful enantioselectivities (er up to 91:9). The produced α-arylalkanoates were readily converted to the corresponding α-arylalkanoic acids with high optical enrichment (er up to >99:1) via simple deprotections/recrystallizations. The results of radical probe experiments are consistent with a mechanism that involves the formation of an alkyl radical intermediate, which undergoes subsequent enantioconvergent arylation in an intermolecular manner. The developed asymmetric coupling offers not only facile and practical access to various chiral α-arylalkanoic acid derivatives, which are of significant pharmaceutical importance, but also a basis of controlling enantioselectivity in an iron-catalyzed organometallic transformation. (Chemical Equation Presented).
- Jin, Masayoshi,Adak, Laksmikanta,Nakamura, Masaharu
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supporting information
p. 7128 - 7134
(2015/06/25)
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- Chiron based synthesis of isocoumarins: Reactivity of α-substituted carboxylic acids
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The asymmetric synthesis of a novel (S)-isocoumarin has been attempted in a single step by the coupling of homophthalic acid with (S)-N-protected amino acids and α-chloroacids at high temperature by exploiting a chiral pool methodology. The coupling of homophthalic acid with N-protected (S)-amino acids gave exclusion of the carboxyl/alkyl group. However, coupling of homophthalic acid with α-chloroacids afforded asymmetric isocoumarins in high yield.
- Saddiqa, Aisha,Raza, Abdul R.,Black, David Stc.,Kumar, Naresh
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p. 736 - 743
(2014/06/09)
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- Stereoselective synthesis of (3r)-3-alkyl-4,1-benzoxazepine-2,5-diones
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Novel 3-alkyl-4,1-benzoxazepine-2,5-diones were synthesized in good ee exploiting the chiral pool methodology, an economical way of asymmetric synthesis. Various anthranilic acids are coupled with different α-haloacids to afford N-acylated anthranilic aci
- Nisar, Bushra,Raza, Abdul Rauf,Black, David Stc.,Kumar, Naresh,Tahir, Muhammad Nawaz
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p. 865 - 870
(2014/01/06)
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- Enantioselective CC bond reduction of unsaturated α-chloro esters by old yellow enzymes
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The reduction of the CC double bond of some unsaturated α-chloro esters was investigated by means of cloned and overexpressed enoate reductases. The results were compared with those obtained by employing baker's yeast whole cells. The anti stereochemistry of hydrogen additions was confirmed by deuterium labeling experiments.
- Brenna, Elisabetta,Fronza, Giovanni,Fuganti, Claudio,Monti, Daniela,Parmeggiani, Fabio
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experimental part
p. 17 - 21
(2012/02/05)
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- Synthesis of azide-alkyne fragments for "Click" chemical applications. Part 2. Formation of oligomers from orthogonally protected chiral trialkylsilylhomopropargyl azides and homopropargyl alcohols
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(Chemical Equation Presented) A small library of chiral, β3-substituted homopropargyl alcohols and chiral β3-substituted trimethylsilylhomopropargyl azides were generated starting from natural L-amino acids. The free alkynes and azides were then coupled, using a Huisgen 1,3-dipolar cycloaddition, to provide chiral oligomeric 1,4-disubstituted-1,2,3-triazoles as potential peptidomimetic compounds. The work is an extension to the previous synthesis of racemic, orthogonally protected 1,4-disubstituted-1,2,3-triazoles from the corresponding α-substituted propargyl alcohols and α-substituted trialkylsilylpropargyl azides.
- Montagnat, Oliver D.,Lessene, Guillaume,Hughes, Andrew B.
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scheme or table
p. 390 - 398
(2010/03/30)
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- Stereoselective synthesis of chiral 4-(1-Chloroalkyl)-β-lactams starting from amino acids and their transformation into functionalized chiral azetidines and pyrrolidines
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Chiral short-chain α-chloroaldehydes were prepared starting from enantiomerically pure amino acids in a three-step approach, thus providing a practical synthetic alternative for known organocatalytic α-chlorination procedures. The latter aldehydes proved
- Dekeukeleire, Stijn,Dhooghe, Matthias,Toernroos, Karl W.,De Kimpe, Norbert
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experimental part
p. 5934 - 5940
(2010/11/05)
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- An unusual conformation of α-haloamides due to cooperative binding with zincated porphyrins
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CD and NMR spectroscopic evidence of cooperative binding between an α-halogen atom and a carboxamide group with a zinc porphyrin leads to an unprecedented conformation for the determination of the absolute stereochemistry of α-haloamides (α-halocarboxylic acids derivatized with 1,4-phenylenediamine) through the use of exciton-coupled circular dichroism (ECCD). With the use of chiral lactams, whose rotomeric contributions are minimized, both ECCD and NMR spectroscopy demonstrate that the porphyrin favors binding to the side of the sterically more demanding halogen atom as compared to the smaller hydrogen atom. In all, the data is strongly suggestive of an unusual conformation not observed before for α-chiral amides. A mnemonic for determining the absolute stereochemistry of α-halogenated carboxylic acids is provided.
- Tanasova, Marina,Yang, Qifei,Olmsted, Courtney C.,Vasileiou, Chrysoula,Li, Xiaoyong,Anyika, Mercy,Borhan, Babak
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supporting information; experimental part
p. 4242 - 4253
(2011/02/25)
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- Liquid crystal dimers derived from naturally occurring chiral moieties: synthesis and characterization
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Naturally occurring cholesterol and α-chloroalkanoyl units derived from natural α-amino acids (l-valine, l-leucine, and l-isoleucine) have been utilized to prepare three different series of nonsymmetric liquid crystal dimers. Tolane (diphenylacetylene), w
- Yelamaggad, Channabasaveshwar V.,Shanker, Govindaswamy
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p. 3760 - 3771
(2008/09/20)
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- Design and synthesis of chromogenic thiopeptolide substrates as MetAPs active site probes
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Twenty one chromogenic thiopeptolide substrates were designed and synthesized as the active site probes and analyzed with each S1 site of mutant residues and enzymes of wild-type MetAP1s. The preliminary enzymatic experiments indicate that cysteine 70 or 202, at either Escherichia coli or human MetAP1, played a crucial role in the methionine hydrolysis.
- Cui, Yong-Mei,Li, Jing-Ya,Chen, Ling-Ling,Li, Jia,Ye, Qi-Zhuang,Nan, Fa-Jun
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p. 2853 - 2861
(2007/10/03)
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- Thermal behaviour and mesophase structure of cyclic oligosiloxanes with chiral mesogenic groups
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Chiral, smectogenic pendant groups have been covalently attached to cyclic oligosiloxanes by hydrosilylation. Differential scanning calorimetry, optical polarising microscopy, and X-ray diffraction measurements reveal liquid crystalline properties for all
- Soltysiak, Joanna T.,Bialecka-Florjanczyk, Ewa,Kowalczyk, Ewa,Przedmojski, Jan
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p. 217/[1259]-230/[1272]
(2007/10/03)
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- Tilt-polarization coupling in a homologous series of ferroelectric liquid crystals
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The synthesis of the homologous series 4-[(S)-2-chloro-4-methylpentanoyloxy]-4′-[4-alkylbenzoyloxy]biphenyl and their chiral and mesomorphic properties are reported. The enantiomeric excess is deduced from 1H NMR spectroscopy. For the hexyl derivative, a twist grain boundary state (TGBA*) mediates the cholesteric to SmC* phase transition and its stability is discussed in terms of chirality and surface interactions. In the SmC* phase, measurements of the spontaneous polarization are reported and the temperature dependence of the tilt angle is determined from the electro-optical switching process or deduced from X-ray measurements of the smectic layer thickness, respectively. The tilt-polarization coupling is discussed within the framework of the 'generalized Landau model' proposed by Zeks and Blinc.
- Schacht, Jochen,Baethge, Heike,Giesselmann, Frank,Zugenmaier, Peter
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p. 603 - 612
(2007/10/03)
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- Liquid crystalline polymer having a polysiloxane backbone
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A side-chain liquid crystalline polysiloxane having the following formula is disclosed: STR1 wherein Me is methyl; m is an integer of 40 to 80; n is an integer of 1 to 12; Ar is phenylene, biphenylene or naphthalene; Ar' is phenylene or naphthalene; X is halogen or methyl; and R is C1 -C4 alkyl.
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- Asymmetric Synthesis of 2-Chloro- and 2-Bromo-alkanoic acids by Halogenation of α-D-Glucofuranose-Derived Silyl Ketene Acetals.
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Optically active (S)-2-bromo- and 2-chloro-alkanoic acids 6 and 7 have been obtained via the diastereoselective halogenation of chiral silyl ketene acetals 3a-f, and subsequent saponification of the resulting crude esters.Examples characterized by e.e. values up to 95percent are reported.The diastereoface selectivity is independent of the silyl ketene acetal E/Z configuration.
- Angibaud, P.,Chaumette, J. L.,Desmurs, J. R.,Duhamel, L.,Ple, G.,et al.
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p. 1919 - 1932
(2007/10/03)
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- Synthesis and study of new α-haloacid ferroelectric liquid crystal derivatives. MM2 approach to the molecular structure-ferroelectric activity relationship
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In order to understand the structural factors that influence ferroelectric properties, three new series (F, Cl, and Br) of chiral naphthalene-ring derived compounds were synthesized, and their ferroelectric properties [spontaneous polarization (Ps) and response time (τ)] were evaluated in the pure compound. The chiral tails are α-halo acids derived from L-α-amino acids: L-α-alanine (1), L-leucine (2), L-isoleucine (3), and L-valine (4), with a fluorine, chlorine, or bromine atom in the chiral center. The highest Ps values were obtained for compounds containing a fluorine or chlorine atom in their asymmetric center and with chiral tail derived from L-isoleucine (3) (F-3, 102 nC/cm2; Cl-3, 100 nC/cm2). The steric requirements of the halogen atom and the bulky alkyl group in the asymmetric center determine the most stable conformations of these chiral tails, which have been studied by molecular mechanic empirical calculations, MM2. MM2 calculations prove to be a successful tool for understanding how the structure of the lateral chiral tail affects molecular arrangement and, as a consequence, the ferroelectric properties of the materials.
- Sierra,Serrano,Ros,Ezcurra,Zubía
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p. 7645 - 7651
(2007/10/02)
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- Enantiomeric Recognition of Organic Ammonium Salts by Chiral Dialkyl-, Dialkenyl-, and Tetramethyl-Substituted Pyridino-18-crown-6 and Tetramethyl-Substituted Bis-pyridino-18-crown-6 Ligands: Comparison of Temperature-Dependent 1H NMR and Empirical Force
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Six new chiral pyridino-18-crown-6 and one chiral bis-pyridino-18-crown-6 ligands have been prepared.The pyridino-crowns contain either two isopropyl, two isobutyl, two (S)-sec-butyl, two benzyl, two 3-butenyl, or four methyl substituents on chiral macror
- Bradshaw, Jerald S.,Huszthy, Peter,McDaniel, Christopher W.,Zhu, Cheng Y.,Dalley, N. Kent,et al.
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p. 3129 - 3137
(2007/10/02)
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- STEREOCONTROLLED SYNTHESIS OF D-α-HYDROXY CARBOXYLIC ACIDS FROM L-AMINO ACIDS
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Optically active D-α-hydroxy carboxylic acids are obtained from L-amino acids via L-α-halocarboxylic acids and their stereoselective reaction with cesium p-nitrobenzoate.
- Kunz, Horst,Lerchen, Hans-Georg
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p. 1873 - 1876
(2007/10/02)
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- The Determination of Small Amounts of Enantiomeric Impurities in α-Halo Carboxylic Acids
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The accurate determination of the enantiomeric composition of α-halo carboxylic acids is reported.Such data are of importance in the synthesis of chiral compounds and in mechanistic studies involving the title compounds.
- Watabe, K.,Chang, S.-C.,Gil-Av, E.,Koppenhoefer, B.
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p. 225 - 228
(2007/10/02)
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- FERROELECTRIC SC* PHASE IN SOME BENZOATE SERIES
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Several homologous benzoate series which exhibit ferroelectric smectic SC* phases have been synthesized.The used chiral acid chains were prepared from commercially available α-amino acids.The series allow us to determine the influence of the size of the substituent of the chiral carbon on the existence and the stability of the SC* phase.They also give some compounds or mixtures which display high spontaneous polarization.
- Tinh, Nguyen Huu,Salleneuve, C.,Babeau, A.,Galvan, J. M.,Destrade, C.
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p. 147 - 154
(2007/10/02)
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- Asymmetric Transformation of 2-Phenyl- and 2-Chloroalkanoic Acids via Chiral Oxazolines
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Asymmetric transformation of racemic 2-phenyl- and 2-chloroalkanoic acids via oxazolines into the corresponding optically active acids was investigated using (S)-phenylalaninol as a chiral auxiliary.The asymmetric transformation was performed by metalatio
- Shibata, Saizo,Matsushita, Hajime,Kaneko, Hajime,Noguchi, Masao,Saburi, Masahiko,Yoshikawa, Sadao
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p. 3546 - 3551
(2007/10/02)
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