Synthesis and biological evaluation of novel N-α-haloacylated homoserine lactones as quorum sensing modulators

• Michail Syrpas,
• Ewout Ruysbergh,
• Christian V. Stevens,
• Norbert De Kimpe and
• Sven Mangelinckx

Beilstein J. Org. Chem. 2014, 10, 2539–2549, doi:10.3762/bjoc.10.265

• of these possible conformational effects, combined with the electron-withdrawing effect of the halogens, will be subject of future theoretical calculations. Due to the presence of the halogen as an electrophilic moiety, it could be possible that the reduced activity of the novel halogenated analogues

Towards the sequence-specific multivalent molecular recognition of cyclodextrin oligomers

• Michael Kurlemann and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2014, 10, 2428–2440, doi:10.3762/bjoc.10.253

• result in different steric environments during the interactions, but the exact effects cannot be predicted and have to be solved by theoretical calculations and simulations. In the last step the interactions of the trivalent guest strands 11, 12, 13 and 14 with complementary and non-complementary

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

Stereocontrolled synthesis of 5-azaspiro[2.3]hexane derivatives as conformationally “frozen” analogues of L-glutamic acid

• Beatrice Bechi,
• David Amantini,
• Cristina Tintori,
• Maurizio Botta and
• Romano di Fabio

Beilstein J. Org. Chem. 2014, 10, 1114–1120, doi:10.3762/bjoc.10.110

• partial facial selectivity was observed in favor of the Si face attack (ratio 20a:20c = 1.5:1). To explain the results, the relative stability of the four diastereoisomers 20a–d was assessed by theoretical calculations. 10000 conformations were generated for each molecule by using the mixed torsional/low

• acetate. The cyclopropanation reaction occurred with trans selectivity preferentially affording the two trans cyclopropane products. Theoretical calculations on the stability of the four possible diastereoisomers were in agreement with both literature and experimental data observed. The final constrained

Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

• Josué M. Silla,
• Claudimar J. Duarte,
• Rodrigo A. Cormanich,
• Roberto Rittner and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2014, 10, 877–882, doi:10.3762/bjoc.10.84

• phase and in implicit water through theoretical calculations. Despite the presence of σCH→σ*CF and σCH→σ*CN interactions, which usually rule the hyperconjugative gauche effect in 1,2-disubstituted ethanes, the most important forces leading to the double gauche effect (+NH3 in the gauche relationship

• a 2-substituted ethylamine fragment [1][2][3][4][5]. According to theoretical calculations, such conformational preference takes place in the gas phase and persists in water solution, where most biochemical processes occur. We have recently shown that, in water solution, the axial preference of 3

• through theoretical calculations and infrared spectroscopy [11]. No significant double gauche effect has been found in 1, since conformers possessing two fluorine atoms in the gauche relationship with the amino group (gauche-gauche, gg) are estimated to be similarly populated to those conformers with only

Staudinger ligation towards cyclodextrin dimers in aqueous/organic media. Synthesis, conformations and guest-encapsulation ability

• Malamatenia D. Manouilidou,
• Yannis G. Lazarou,
• Irene M. Mavridis and
• Konstantina Yannakopoulou

Beilstein J. Org. Chem. 2014, 10, 774–783, doi:10.3762/bjoc.10.73

• titration experiments: the binding constant with 1-adamantylamine was similar to that of natural β-CD. Theoretical calculations for isolated molecules (PM3 level of theory) and in the presence of solvent [water, PM3(COSMO)] as well as DFT calculations suggested that the compounds prefer to adopt

• characterization combined with theoretical calculations, revealed the full capacity of the cavities for molecular inclusion despite the dynamic equilibria between closed and open conformations of the products in water. Results and Discussion Synthesis – The Staudinger ligation via linker 2 (Scheme 2) was initially

• formation in one step. Despite the well verified formation of intra- as well as intermolecular inclusion complexes, the compounds proved to be effective in encapsulating a suitable external guest in each cavity. The data were fully supported by theoretical calculations that confirmed the energetic

Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

• Denisa Tarabová,
• Stanislava Šoralová,
• Martin Breza,
• Marek Fronc,
• Wolfgang Holzer and
• Viktor Milata

Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70

• obtained from theoretical calculations at 293.15 K. However, the calculated proportion of tautomers does not include the effects of the reaction conditions and kinetics factors on the final proportion of individual tautomers in solution. Total electronic IEFPCM-B3LYP/6-311++G** energies with zero-point

Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

• Yuta Takano,
• Yuki Nagashima,
• M. Ángeles Herranz,
• Nazario Martín and
• Takeshi Akasaka

Beilstein J. Org. Chem. 2014, 10, 714–721, doi:10.3762/bjoc.10.65

• . Although the structure of 5b was not elucidated using X-ray crystallographic analysis, synthetic precedents with absorption spectral data and theoretical calculations [16] strongly suggest that the most feasible addition site of the addend is that indicated in Scheme 2. The thermodynamic stability of 5b

New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions

• Helge Klare,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2014, 10, 224–236, doi:10.3762/bjoc.10.18

• supplementary crystallographic data for this compound. Computational details All theoretical calculations were performed with the program package TURBOMOLE-6.3 [48]. The employed density functionals was the nonempirical TPSS-functional developed by Tao, Perdew, Scuseria and Staroverov [49], combined with the

3-Pyridinols and 5-pyrimidinols: Tailor-made for use in synergistic radical-trapping co-antioxidant systems

• Luca Valgimigli,
• Daniele Bartolomei,
• Riccardo Amorati,
• Evan Haidasz,
• Jason J. Hanthorn,
• Susheel J. Nara,
• Johan Brinkhorst and
• Derek A. Pratt

Beilstein J. Org. Chem. 2013, 9, 2781–2792, doi:10.3762/bjoc.9.313

• 4-position relative to the reactive hydroxyl moiety. Due to steric interactions between the adjacent ring methyl, the dimethylamino substituent in 4c is rotated out of the plane of the aromatic ring [17]. On the basis of theoretical calculations, H-atom transfer between phenol and the phenoxyl

• slow the analogous reaction between the radical derived from 4c and 11 relative to the other reaction couples. However, it should be pointed out that theoretical calculations on the phenol/phenoxyl H-atom transfer reaction do not include substituents in the ortho positions relative to the phenolic

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• the key role of intramolecular hydrogen bond (H-bond) interactions for both reactivity and stereoselectivity [65]. Theoretical calculations and experimental evidences ruled out the SN1 reaction mechanism via allylic carbocation. Experiments with stereodefined hydroxy allylic alcohols revealed that the

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• experimental data as well as theoretical calculations suggested that both cycloadducts, 14 and 15, arise from the same intermediate, the cycloheptanyl metal–carbene species VIII, which might evolve through a 1,2-hydrogen shift to give the seven-membered carbocycles 14 (Scheme 8, a), or by a ring-contraction

Flow synthesis of phenylserine using threonine aldolase immobilized on Eupergit support

• Jagdish D. Tibhe,
• Hui Fu,
• Timothy Noël,
• Qi Wang,
• Jan Meuldijk and
• Volker Hessel

Beilstein J. Org. Chem. 2013, 9, 2168–2179, doi:10.3762/bjoc.9.254

• microreactor. Analysis of the four isomers of phenylserine on a chiral column. Phenylserine synthesis. Synthesis of chiral α-aminoalcohol by telescoping aldolase reaction with decarboxylation. Comparison of direct and indirect method. Comparison of productivity between the theoretical calculations and

Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring

• Marta Pérez-Torralba,
• Rosa M. Claramunt,
• M. Ángeles García,
• Concepción López,
• M. Carmen Torralba,
• M. Rosario Torres,
• Ibon Alkorta and
• José Elguero

Beilstein J. Org. Chem. 2013, 9, 2156–2167, doi:10.3762/bjoc.9.253

• -033; email: deposit@ccdc.cam.ac.uk). Theoretical calculations. The geometry of the molecules has been fully optimized with the hybrid HF/DFT B3LYP [29][30][31] computational method and the 6-31G(d) basis set [32]. Frequency calculations have been carried out at the same computational level to verify

Thermochemistry and photochemistry of spiroketals derived from indan-2-one: Stepwise processes versus coarctate fragmentations

• Götz Bucher,
• Gernot Heitmann and
• Rainer Herges

Beilstein J. Org. Chem. 2013, 9, 1668–1676, doi:10.3762/bjoc.9.191

• chelotropic elimination of 1,3-dioxolan-2-ylidene is not likely. This carbene has been generated from a norbornadiene spiro ketal, and it cleanly fragmented into CO2 and ethylene [30]. Theoretical calculations support the low barrier for fragmentation [31]. We explain the different reaction behaviour of our

Conformational analysis and intramolecular interactions in monosubstituted phenylboranes and phenylboronic acids

• Josué M. Silla,
• Rodrigo A. Cormanich,
• Roberto Rittner and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2013, 9, 1127–1134, doi:10.3762/bjoc.9.125

• goals, NMR spectroscopy (by means of suitable coupling constants) and theoretical calculations were used. Second-order perturbation analysis of donor–acceptor interactions in the natural bond orbitals (NBO) was used to interpret conformational isomerism in terms of hyperconjugative interactions, in such

• ca. 2 mg mL−1 in benzene-d6 and 20 mg mL−1 in CD3CN solutions. The infrared spectrum was acquired in a BOMEM MB100 spectrometer from 0.1 M CDCl3 solution, using a liquid cell with NaCl windows and 0.5 mm spacer, collecting 32 scans at 1 cm−1 resolution. For the theoretical calculations, a Monte Carlo

An aniline dication-like transition state in the Bamberger rearrangement

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2013, 9, 1073–1082, doi:10.3762/bjoc.9.119

• rearrangement. Theoretical calculations The reacting systems were investigated by density functional theory (DFT) calculations. The B3LYP [8][9] method was used to trace the reaction path. The basis sets employed were 6-31G(d) and 6-311+G(d,p), where the latter was adopted for the key (OH transfer) steps. For

Synthesis, photophysical and electrochemical characterization of terpyridine-functionalized dendritic oligothiophenes and their Ru(II) complexes

• Amaresh Mishra,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2013, 9, 866–876, doi:10.3762/bjoc.9.100

• further supported by theoretical calculations (see below). For ligands 8 and 9, with increasing generation of the dendron from G1 and G2, a slight red-shift in the lowest energy absorption maximum and a significant enhancement in the molar absorption coefficient were observed. Furthermore, the absorption

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

• Rajendra K. Jangid,
• Nidhi Sogani,
• Neelima Gupta,
• Raj K. Bansal,
• Moritz von Hopffgarten and
• Gernot Frenking

Beilstein J. Org. Chem. 2013, 9, 392–400, doi:10.3762/bjoc.9.40

• DA reactions of 2-phosphaindolizine-η1-P-AlEtCl2 complexes [21]. Theoretical calculations at the DFT (B3LYP/6-31+G**) level indicated lowering of the activation barrier by 6 kcal mol–1 for the reaction of σ2,λ3-P-coordinated 2-phosphindolizine to methylaluminium dichloride with 1,3-butadiene as

Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions

• Matthias Leven,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18

• measurements were repeated three times and three samples were prepared to give identical results. Computational details. All theoretical calculations were performed with the program package TURBOMOLE-6.3 [34]. The employed density functionals were the nonempirical TPSS-functional developed by Tao, Perdew

Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• biradical BR2 with a conformation that is unfavorable for oxirane formation, but enables efficient hydrogen migration to result in aldehyde 3a. Theoretical calculations have confirmed that acetaldehyde derivatives may be formed upon rearrangement of the 1,3-oxyethandiyl [20][21] and that a subsequent

Enantioselective supramolecular devices in the gas phase. Resorcin[4]arene as a model system

• Caterina Fraschetti,
• Matthias C. Letzel,
• Antonello Filippi,
• Maurizio Speranza and
• Jochen Mattay

Beilstein J. Org. Chem. 2012, 8, 539–550, doi:10.3762/bjoc.8.62

• experimentally considered: The configuration of the amine B and that of the guest G. According to theoretical calculations, the chiral effects are insignificant if the guest molecule in the [YS∙H∙G]+ complex is located outside the cavity of the host, while a bimodal kinetic is mirrored by the coexistence of a

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• is remarkable. In this geometry, however, p(Cylide)–σ*(S–C) conjugation of the unshared pair of electrons at the ylidic carbon atom would be feasible. While this interaction is a key stabilisation factor for the parent sulfonium ylides (e.g., H2S–CH2 and Me2S–CH2) according to theoretical

• calculations [24], its energetic contribution in the case of sulfonium ylides stabilised by acceptor substituents is likely to be small. The oxazapolycycles 13a and b are head-to-tail dimers of carbonyl ylides, resulting from a [3 + 3]-cycloaddition. Their constitution and relative stereochemistry was assigned

Synthesis of multivalent host and guest molecules for the construction of multithreaded diamide pseudorotaxanes

• Nora L. Löw,
• Egor V. Dzyuba,
• Boris Brusilowskij,
• Lena Kaufmann,
• Elisa Franzmann,
• Wolfgang Maison,
• Emily Brandt,
• Daniel Aicher,
• Arno Wiehe and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2012, 8, 234–245, doi:10.3762/bjoc.8.24

• view of previous theoretical calculations on amide/tetralactam macrocycle complexes [111], which show that simple amide axles dethread in the gas phase because of a favourable entropy term arising from the increase in particle number upon complex dissociation. This entropic contribution overcompensates

Computational evidence for intramolecular hydrogen bonding and nonbonding X···O interactions in 2'-haloflavonols

• Tânia A. O. Fonseca,
• Matheus P. Freitas,
• Rodrigo A. Cormanich,
• Teodorico C. Ramalho,
• Cláudio F. Tormena and
• Roberto Rittner

Beilstein J. Org. Chem. 2012, 8, 112–117, doi:10.3762/bjoc.8.12

• interactions; theoretical calculations; Introduction Intermolecular hydrogen bonding (HB) is an interaction governing self-assembly and is responsible for the architecture and organization of molecular aggregates [1], and also ligand–receptor interactions that are responsible for the bioactivity of compounds

• (antioxidant, anti-inflammatory, antiviral, etc.) [12]. The goal of this work is to understand the intramolecular forces determining the preferred conformations of these molecules through the use of DFT theoretical calculations, quantum theory of atoms in molecules (QTAIM) [13][14][15][16][17] and natural bond