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Treatment of 3‐methylamino‐5‐phenylthiophene with α,β‐unsaturated esters, i.e., methyl acrylate, (E)‐methyl crotonate, diethyl fumarate, diethyl maleate and ethyl propiolate, in tetrahydrofuran for several days at reflux gave 1‐methyl‐3,4‐dihydrothieno[2,3‐e]pyridin‐2‐ones 4 and/or 1‐methylthieno[2,3‐e]pyridin‐2‐ones 5 , depending on the structure of the esters. On the other hand, the same reactions with α,β‐unsaturated nitriles such as acrylonitrile and tetracyanoethene, gave the corresponding thiophenes 7 and 10 bearing 2‐cyanoethyl and 1,2,2‐tricyanoethenyl groups at C‐2, respectively. The reaction with (Z)‐1,2‐dicyanoethene under the same conditions produced the corresponding thiophene 9 bearing the 1,2‐dicyanoethenyl group and 1,2‐dicyano‐5‐methylaminobiphenyl. 相似文献
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Synthesis of new optically active α,α′,β‐trisubstituted‐β‐lactones as monomers for stereoregular biopolyesters 下载免费PDF全文
Rima Belibel Christel Barbaud 《Journal of polymer science. Part A, Polymer chemistry》2015,53(22):2586-2597
Various optically active (4R)‐alkyloxycarbonyl‐3,3‐dialkyl‐2‐oxetanones as monomers were synthesized from L‐(S)‐malic acid in six steps to prepare a new family of stereopolyesters for biomedical applications. The synthesis began with an esterification followed of a dialkylation in the aim to introduce hydrophobic groups as methyl or reactive group as allyl. Then, a saponification has permitted to obtain the corresponding diacids that reacted with appropriate alcohols to furnish different monoesters. The last and most important step was activation of hydroxyl group of monoesters with the asymmetric carbon configuration inversion according to the Mitsunobu reaction. Thus, this reaction has provided lactones from monoesters with 100% enantiomeric excess which was confirmed by 1H NMR and by the synthesis of corresponding isotactic and semicrystalline homopolyesters. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2586–2597 相似文献
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L. C. R. Andrade J. A. Paixo M. J. M. De Almeida F. M. Fernandes Roleira E. J. Tavares da Silva 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(3):o131-o133
The title compounds, both C23H34O5, are the 5α and 5β configurations of two diacetate epimers. The 5β‐diacetate crystallizes in an hexagonal structure, unusual for steroid molecules. The unit cell has an accessible solvent volume of 358 Å3, responsible for clathrate behaviour. The 5β‐epimer also features some shorter than average bond lengths in the 3α,4β‐acetoxy groups. The conformations of the molecules of both epimers are compared with those obtained through abinitio quantum chemistry calculations. Cohesion of the crystals can be attributed to van der Waals and weak molecular C—H⋯O interactions. 相似文献
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The reaction of Ph3P=NLi with various α,β‐unsaturated esters gives access to new N‐(α,β‐unsaturated acyl) phosphinimines, which can undergo intramolecular aza‐Wittig reactions (at 65–110°C) to afford the corresponding nitriles. The structures of all new compounds were established by elementary analyses, IR, 1H‐, 13C‐, and 31P‐NMR spectroscopy. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 49–54, 1999 相似文献
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Magnus Frnbck Lars Eriksson Gran Widmalm 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):700-701
The structure of the title compound, C28H38O18S, has been determined. The torsion angles of the glycosidic linkage in the non‐reducing disaccharide, ?H and ?H′, have values of 3 and 53°, respectively. The latter torsion angle is in agreement with the exo‐anomeric effect, whereas the former shows an eclipsed conformation. Both glycopyranosyl residues adopt a slightly distorted chair conformation. 相似文献
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Paulo J. Amorim Madeira Ana Margarida Rosa Nuno M. Xavier Amélia P. Rauter M. Helena Florêncio 《Rapid communications in mass spectrometry : RCM》2010,24(7):1049-1058
Knowledge of the fragmentation mechanisms of lactones and their behaviour under electrospray ionization (ESI) conditions can be extended to larger and more complex natural products that contain an α,β‐unsaturated γ‐lactone moiety in their structure. Moreover, little is known about the gas‐phase behaviour of α,β‐unsaturated γ‐lactones linked or fused to sugars. Therefore, five α,β‐unsaturated γ‐lactones (butenolides) fused to a pyranose ring, recently synthesized compounds with potential relevance regarding their biological properties, were investigated using ESI‐MS and ESI‐MS/MS in both positive and negative ion modes. Their fragmentation mechanisms and product ion structures were compared. It was observed that two isomers could be unambiguously distinguished in the negative ion mode by the fragmentation pathways of their deprotonated molecules as well as in the positive ion mode by the fragmentation pathways of either the protonated or the sodiated molecule. Fragmentation mechanisms are proposed taking into account the MS/MS data and semi‐empirical calculations using the PM6 Hamiltonean. The semi‐empirical calculations were also very useful in determining the most probable protonation and cationization sites. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Piotr Przybylski Krystian Pyta Joanna Stefańska Bogumil Brzezinski Franz Bartl 《Magnetic resonance in chemistry : MRC》2010,48(4):286-296
Four new hydroxy‐aminoalkyl derivatives of α,β‐unsaturated macrolide‐josamycin (2–5) have been synthesised and their structures have been studied by means of 1H and 13C NMR and FT‐IR methods. Complete assignment of resonances in the 1H and 13C NMR spectra has been made on the basis of 1H? 13C HSQC, 1H? 13C HMBC, 1H? 1H COSY, 1H? 1H NOESY 2D experiments. Spectroscopic data indicated that for the derivatives 3 and 4 some equilibrium between two different structures exists in contrast to derivatives 2 and 5. The lowest‐energy structures of the new derivatives of josamycin have been calculated and visualised by PM5 method at semi‐empirical level of theory, taking into account the NMR and FT‐IR data. The most significant differences between the structures of josamycin and its newly synthesised derivatives' were found in the conformation of the macrolide aglycone part and in the mutual orientation of the 4‐O‐isovalerylmycarosylmycaminose moiety relative to the aglycone part. PM5 semi‐empirical calculations indicated that the structures of the new macrolide derivatives are stabilised by rather weak intramolecular hydrogen bonds in agreement with spectroscopic data. Antimicrobial properties of the new derivatives 2–5 as well as those having an acetate group at C‐3 (6 and 7) were determined and compared to that of the parent macrolide antibiotic josamycin (1). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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A preparatively useful one‐step transformation of γ,γ‐disubstituted α‐formyl‐γ‐lactones into trisubstituted γ,δ‐unsaturated aldehydes is described, by means of catalytic amounts of either AcOH or AcOEt in the vapor phase over a glass support. A mechanistic rationale is proposed. 相似文献
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The utility of diphenylphosphonoacetamides [(PhO)2P(O)CH2CONRR′] as Horner–Wadsworth–Emmons reagents was examined with five different patterns of substitution upon the amide nitrogen atom ( 2a : R, R′ = CH2Ph; 2b : R = CH2Ph, R′ = H; 2c : R = Me, R′ = OMe; 2d : R, R′ = Ph; 2e : R, R′ = (CH2)4). The reaction of 2a was found to be Z‐selective for aromatic aldehydes with selectivities up to 95:5. Reagent 2b led to reasonable selectivity for both benzaldehyde (85:15) and 3‐phenylpropionaldehyde (87:13), while 2c was somewhat effective for only the latter alkyl aldehyde (83:17). Compounds 2d and 2e exhibited slightly lower selectivities compared with 2a . © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:515–523, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20054 相似文献
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J. I. F. Paixo J. A. R. Salvador J. A. Paixo A. Matos Beja M. Ramos Silva A. M. d'A. Rocha Gonsalves 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(9):o630-o632
In the title compound, C21H31N3O4, a potential inhibitor of aromatase, all rings are fused trans. Rings A, B and C have chair conformations which are slightly flattened. Ring D has a 14α‐envelope conformation. The steroid nucleus has a small twist, as shown by the C19—C10⋯C13—C18 torsion angle of 6.6 (2)°. Ab initio calculations of the equilibrium geometry of the molecule reproduce this small twist, which appears to be due to the steric effect of the 6β‐azide substituent rather than to packing effects. 相似文献
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G. Raju V. Ramesh R. Srinivas G. V. M. Sharma B. Shoban Babu 《Journal of mass spectrometry : JMS》2010,45(6):651-663
Two new series of Boc‐N‐α,δ‐/δ,α‐ and β,δ‐/δ,β‐hybrid peptides containing repeats of L ‐Ala‐δ5‐Caa/δ5‐Caa‐L ‐Ala and β3‐Caa‐δ5‐Caa/δ5‐Caa‐β3‐Caa (L ‐Ala = L ‐alanine, Caa = C‐linked carbo amino acid derived from D ‐xylose) have been differentiated by both positive and negative ion electrospray ionization (ESI) ion trap tandem mass spectrometry (MS/MS). MSn spectra of protonated isomeric peptides produce characteristic fragmentation involving the peptide backbone, the Boc‐group, and the side chain. The dipeptide positional isomers are differentiated by the collision‐induced dissociation (CID) of the protonated peptides. The loss of 2‐methylprop‐1‐ene is more pronounced for Boc‐NH‐L ‐Ala‐δ‐Caa‐OCH3 (1), whereas it is totally absent for its positional isomer Boc‐NH‐δ‐Caa‐L ‐Ala‐OCH3 (7), instead it shows significant loss of t‐butanol. On the other hand, second isomeric pair shows significant loss of t‐butanol and loss of acetone for Boc‐NH‐δ‐Caa‐β‐Caa‐OCH3 (18), whereas these are insignificant for its positional isomer Boc‐NH‐β‐Caa‐δ‐Caa‐OCH3 (13). The tetra‐ and hexapeptide positional isomers also show significant differences in MS2 and MS3 CID spectra. It is observed that ‘b’ ions are abundant when oxazolone structures are formed through five‐membered cyclic transition state and cyclization process for larger ‘b’ ions led to its insignificant abundance. However, b1+ ion is formed in case of δ,α‐dipeptide that may have a six‐membered substituted piperidone ion structure. Furthermore, ESI negative ion MS/MS has also been found to be useful for differentiating these isomeric peptide acids. Thus, the results of MS/MS of pairs of di‐, tetra‐, and hexapeptide positional isomers provide peptide sequencing information and distinguish the positional isomers. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Nilo Zanatta Elizandra C. S. Lopes Leonardo Fantinel Helio G. Bonacorso Marcos A. P. Martins 《Journal of heterocyclic chemistry》2002,39(5):943-947
The synthesis of a novel series of twelve 4‐(trihalomethyl)dipyrimidin‐2‐ylamines, from the cyclo‐condensation reaction of 4‐(trichloromethyl)‐2‐guanidinopyrimidine, with β‐alkoxyvinyl trihalomethyl ketones, of general formula: X3C‐C(O)‐C(R2)=C(R1)‐OR, where: X = F, Cl; R = Me, Et, ‐(CH2)2‐, ‐(CH2)3‐; R1 = H, Me; R2 = H, Me, ‐(CH2)2‐, ‐(CH2)3‐, is reported. The reactions were carried out in acetonitrile under reflux for 16 hours, leading to the dipyrimidin‐2‐ylamines in 65‐90% yield. Depending on the substituents of the vinyl ketone, tetrahydropyrimidines or aromatic pyrimidine rings were obtained from the cyclization reaction. When X = Cl, elimination of the trichloromethyl group was observed during the cyclization step. The structure of 4‐(trihalomethyl)dipyrimidin‐2‐ylamines was studied in detail by 1H‐, 13C‐ and 2D‐nmr spectroscopy. 相似文献
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Lophenol, cholest-4α-methyl-7-en-3β-ol (1), obtained from Dracaena cochinchinensis (Lour.) S. C. Chen, was structurally modified. It was acetylated to protect 3β-hydroxyl group, and then oxidised by selenium dioxide in acetic acid to give cholest-4a-methyl-8-en-3β, Ta-diol diacetate (3). This compound 3 is unstable in chloroform solution or when heated and easily converted to a diene compound, cholest-4a-methyl-7,14-dien-3β-ol acetate (4). The structures of 3 and 4 were elucidated by means of IR, ^1H NMR, ^13C NMR and MS, and the absolute configuration of 3 was established by X-ray crystallography. The property of 3 was also discussed in this paper. Both 3 and 4 are new compounds and were reported for the first time. 相似文献