The interplay of configuration and conformation in helical perylenequinones: Insights from chirality induction in liquid crystals and calculations

• Elisa Frezza,
• Silvia Pieraccini,
• Stefania Mazzini,
• Alberta Ferrarini and
• Gian Piero Spada

Beilstein J. Org. Chem. 2012, 8, 155–163, doi:10.3762/bjoc.8.16

• found in one of the available X-ray structures of cercosporin [26], whereas the other structure has the methoxy groups in the (m,p) state [28]. Our calculations confirm that the “propeller” form, found in X-ray structures of 1 [26][28], is significantly more stable than the other, called “double

• decrease of the energy differences between conformers, which points to an important role of diffuse functions. Although the conformer population is not directly accessible, we can try to analyze our results in the light of experimental data. Of the two X-ray structures of cercosporin reported in the

• trend reported in Figure 5 (middle). We have also shown in Figure 5 (left) the Q values calculated for the available X-ray structures of cercosporin [26][28]. The differences from the results reported for structures obtained by DFT, with the same conformation of the side chains, derive from relatively

Thermodynamic and kinetic stabilization of divanadate in the monovanadate/divanadate equilibrium using a Zn-cyclene derivative: Towards a simple ATP synthase model

• Hanno Sell,
• Anika Gehl,
• Frank D. Sönnichsen and
• Rainer Herges

Beilstein J. Org. Chem. 2012, 8, 81–89, doi:10.3762/bjoc.8.8

• coordination bond to the Zn2+ ion and two hydrogen bonds to the NH groups of the cyclene ring (Figure 2). The formation of a bidentate complex (two vanadate oxygens coordinating with Zn2+) is considerably less favorable. This is also in agreement with X-ray structures of Zn-cyclene phosphate complexes [15

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• the ligand (R,R)-phenyl-TADDOL (L1)) (Table 2). Consistent catalysis results were obtained when the crystalline Lewis acid complexes K1 and K2 were applied instead of the complexes generated in situ. The synthesis, characterization and X-ray structures of these complexes, which are now commercially

Lithium phosphonate umpolung catalysts: Do fluoro substituents increase the catalytic activity?

• Anca Gliga,
• Bernd Goldfuss and
• Jörg M. Neudörfl

Beilstein J. Org. Chem. 2011, 7, 1189–1197, doi:10.3762/bjoc.7.138

• (racemate); 7: tR = 22.1 min; X-ray structures shown in Figure 1 and Figure 2, respectively) and an additional meso product for diol 8 (HPLC: tR2 = 22.4 min; tR3 = 30.6 min (racemate); tR1 = 9.1 min). A dimer associated by a hydrogen bond is apparent for the enantiomeric pair (6: intermolecular O1–O2

Single enantiomer synthesis of α-(trifluoromethyl)-β-lactam

• Václav Jurčík,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2011, 7, 759–766, doi:10.3762/bjoc.7.86

• Centre as supplementary publication (CCDC 821177). Enantiomers of α-(trifluoromethyl)-β-lactam (1). X-ray structures of (a) β-lactam (S)-1 and (b) (αR,3R)-5c. (a) Determination of the absolute stereochemistry of (αR,3R)-5c by X-ray crystallography allowed an absolute assignment of β-lactam 1. Synthetic

SbCl₃-catalyzed one-pot synthesis of 4,4′-diaminotriarylmethanes under solvent-free conditions: Synthesis, characterization, and DFT studies

• Ghasem Rezanejade Bardajee

Beilstein J. Org. Chem. 2011, 7, 135–144, doi:10.3762/bjoc.7.19

• compound 11, calculated by HF and DFT levels with the HF/6-31G*, 6-31G*/B3LYP, and B3LYP/cc-pVDZ methods, are listed in Table 2. The optimized configuration is shown in Figure 2. Because of unavailability of X-ray crystal structures for these compounds, the optimized structure is compared with X-ray

• structures of similar compounds. This comparison shows good agreement between optimized and actual molecular structures. Here, we compare the bond lengths of the C–C, C–O, and C–N bonds of similar structures with the results of HF/6-31G*, 6-31G*/B3LYP, and B3LYP/cc-pVDZ calculations. The optimized C–C bond

En route to photoaffinity labeling of the bacterial lectin FimH

• Thisbe K. Lindhorst,
• Michaela Märten,
• Andreas Fuchs and
• Stefan D. Knight

Beilstein J. Org. Chem. 2010, 6, 810–822, doi:10.3762/bjoc.6.91

• of its free binding energy. Low (more negative) scores correlate with high affinities, whilst higher scores reflect diminished binding potency (Table 1). Docking was based on two different X-ray structures. In the first case, crystals with an open tyrosine gate were taken as the basis [7], whilst in

• modeling to predict binding of the various FimH ligands was carried out using FlexX flexible docking and consensus scoring as implemented in Sybyl 6.8 as described earlier [20]. Docking was based on published X-ray structures of the FimH CRD. This CRD was held fixed during the minimization, whereas the

A bivalent glycopeptide to target two putative carbohydrate binding sites on FimH

• Thisbe K. Lindhorst,
• Kathrin Bruegge,
• Andreas Fuchs and
• Oliver Sperling

Beilstein J. Org. Chem. 2010, 6, 801–809, doi:10.3762/bjoc.6.90

• of FimH in complex with FimC [8]. The CRD known from X-ray structures at the tip of FimH is coloured in red and can accommodate one α-D-mannosyl residue. A second hypothetical carbohydrate binding region on the protein, as suggested by modeling studies [16], is coloured in brown and represents a more

CAAC Boranes. Synthesis and characterization of cyclic (alkyl) (amino) carbene borane complexes from BF₃ and BH₃

• Julien Monot,
• Louis Fensterbank,
• Max Malacria,
• Emmanuel Lacôte,
• Steven J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2010, 6, 709–712, doi:10.3762/bjoc.6.82

• carbenes. Recently, Bertrand introduced, cyclic (alkyl) (amino) carbenes, or CAACs, as a new class of carbene complex in which the central carbene carbon is stabilized by only one nitrogen atom [20][21][22][23]. Herein we report the synthesis and characterization (including X-ray structures) of two stable

The subtle balance of weak supramolecular interactions: The hierarchy of halogen and hydrogen bonds in haloanilinium and halopyridinium salts

• Kari Raatikainen,
• Massimo Cametti and
• Kari Rissanen

Beilstein J. Org. Chem. 2010, 6, No. 4, doi:10.3762/bjoc.6.4

• hydrogen bond network remains the same, but the halogen bond interaction strength should vary. Surprisingly, the X-ray structures of 10–12 are not polymorphs, in contrast what would be predicted from the series of haloanilinium chlorides (2, 3) or haloanilinium dihydrogenphosphates (6, 7 and 8). The salts

Control of asymmetric biaryl conformations with terpenol moieties: Syntheses, structures and energetics of new enantiopure C₂-symmetric diols

• Y. Alpagut,
• B. Goldfuss and
• J.-M. Neudörfl

Beilstein J. Org. Chem. 2008, 4, No. 25, doi:10.3762/bjoc.4.25

• , (P)-BIVOL, (P)-BICOL, and (P)-BIMEOL. Co-solvent adducts in the X-ray structures of (M)-BIMOL, (P)-BIVOL, (P)-BICOL, and (P)-BIMEOL. Experimental (X-ray crystal structures) and ONIOM(B3LYP/6-31++G**:AM1) computed geometries of BIMOL and BIVOL in P and M biphenyl conformations.a Experimental (X-ray

Understanding the mechanism of Pd-catalyzed allylic substitution of the cyclic difluorinated carbonates

• Jun Xu,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2008, 4, No. 18, doi:10.3762/bjoc.4.18

• electron-withdrawing property of the gem-difluoromethylene group. To further validate our hypothesis and the proposed model of DeShong et al., we decided to explore the crystal structure and 13C NMR of the corresponding Pd-π-allyl complex. In 2000, Bäckvall and co-workers investigated the X-ray structures

The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

• David O'Hagan,
• Henry S. Rzepa,
• Martin Schüler and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

• compounds were prepared by a straightforward EDCI amide coupling between benzylamine and 2,3-difluorosuccinate 19 as shown in Scheme 10. The diasteroisomers of 22 were separated by silica gel chromatography and recrystallisation of each allowed their X-ray structures to be compared. The structure of erythro

An exceptional P-H phosphonite: Biphenyl- 2,2'-bisfenchylchlorophosphite and derived ligands (BIFOPs) in enantioselective copper- catalyzed 1,4-additions

• T. Kop-Weiershausen,
• J. Lex,
• J.-M. Neudörfl and
• B. Goldfuss

Beilstein J. Org. Chem. 2005, 1, No. 6, doi:10.1186/1860-5397-1-6

• -Cl (1). Distances are given in Å. (BAA = biaryl angle between C2-C1-C1'-C2'; FAA-lp = fenchyl-aryl dihedral angle between C1-C2-C3-O1; FAA = fenchyl-aryl dihedral angle between C1'-C2'-C3'-O2). The probability of ellipsoids is 40% (CDC 270531). X-ray structures of BIFOP-Br (2). Distances are given in

• Å. (BAA = biaryl angle between C2-C1-C1'-C2'; FAA-lp = fenchyl-aryl dihedral angle between C1-C2-C3-O1; FAA = fenchyl-aryl dihedral angle between C1'-C2'-C3'-O2). The probability of ellipsoids is 30% (CCDC 270532). X-ray structures of BIFOP-H (3). Distances are given in Å. (BAA = biaryl angle

• between C2-C1-C1'-C2'; FAA-lp = fenchyl-aryl dihedral angle between C1-C2-C3-O1; FAA = fenchyl-aryl dihedral angle between C1'-C2'-C3'-O2). The probability of ellipsoids is 40% (CCDC 270533). X-ray structures of BIFOP-nBu (5). Distances are given in Å. (BAA = biaryl angle between C2-C1-C1'-C2'; FAA-lp