Partial thioamide scan on the lipopeptaibiotic trichogin GA IV. Effects on folding and bioactivity

• Marta De Zotti,
• Barbara Biondi,
• Cristina Peggion,
• Matteo De Poli,
• Haleh Fathi,
• Simona Oancea,
• Claudio Toniolo and
• Fernando Formaggio

Beilstein J. Org. Chem. 2012, 8, 1161–1171, doi:10.3762/bjoc.8.129

• analogues. Conformational analysis A detailed analysis of the spectroscopic properties and conformational preferences of the three monothionated trichogin GA IV analogues synthesized in this work was performed by using CD, FT-IR absorption, and 2D NMR investigations in different solvents. The far- (250–195

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

• asymmetrically substituted carbon atoms in the side chains, gives rise to diastereoisomerism. Cercosporin and phleichrome are characterized by a special coupling between conformation and configuration: The conformational preferences of the side chains in the “1–12 bay region” are critical for the generation of

• literature, one has the side chains in the g+ g+ [28] and the other in the g− g− conformation [26]. These do not appear to be compatible with the strong preference for the trans state predicted by B3LYP calculations, but the conformational preferences in crystals might be biased by the environment. More

• be a suitable technique to determine the axial configuration of perylenequinones. The integration of experiments with the results of calculations at different levels has allowed us to gain an insight into the conformational preferences of the systems under investigation and into the role of

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

• ubiquitous than one imagines and can determine crystal structures [10] and the binding of biological molecules [11] and may possibly be the main forces in determining conformational preferences in molecular systems. 2'-Haloflavonols are important compounds with widespread use as bioactive molecules

• radii are tabulated in [29]), i.e., such a geometric parameter is fulfilled by all of these interactions, indicating the possibility of their formation [30]. Indeed, when considering the Popelier criteria, the HB’s depicted in Figure 2 and Table 2 are stable and, hence, affect the conformational

• preferences of the flavonols under study, except for the C…H(O) interaction of flavonol B (Table 3). The boldface values in the Table 3 are the reference atoms, i.e., hydrogen atoms that have smaller q(H), E(H), M1(H) and V(H) than the reference establish a stable HB. 2'-Fluoroflavonol exhibits four stable

(How) does 1,3,5-triethylbenzene scaffolding work? Analyzing the abilities of 1,3,5-triethylbenzene- and 1,3,5-trimethylbenzene-based scaffolds to preorganize the binding elements of supramolecular hosts and to improve binding of targets

• Xing Wang and
• Fraser Hof

Beilstein J. Org. Chem. 2012, 8, 1–10, doi:10.3762/bjoc.8.1

• conformational preferences of hexaethylbenzene by calculation, NMR, and crystallography and concluded that the conformation bearing alternating up-down arrangement of substituents was the global minimum for this system (Figure 1) [6]. This preference arises from steric gearing of adjacent substituents, which are

NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

• Damjan Makuc,
• Jennifer R. Hiscock,
• Mark E. Light,
• Philip A. Gale and
• Janez Plavec

Beilstein J. Org. Chem. 2011, 7, 1205–1214, doi:10.3762/bjoc.7.140

• recently analyzed the conformational preferences of several 2,7-disubstituted indoles with amide substituents at C2 and urea substituents at C7, which showed preference for distinct conformations in the presence and in the absence of anions [33][34][35]. In addition, indole and urea groups were strongly

• (Table 3). On the other hand, stronger NOE enhancement between H7α and H1 (7.0%) suggested predominance of the syn–anti rotamer of 1 in the presence of chloride anions in DMSO-d6 solution. Interestingly, the syn–syn rotamer was observed in the crystal structure, where conformational preferences are

• H1 and H7α NMR resonances prevented conformational analysis of 2 upon addition of other anions used in the study. The conformational preferences of 2 were evaluated by quantum mechanical calculations at the B3LYP/6-311+G(d,p) level of theory. The freely optimized anti–anti conformer of 2 exhibited

The C–F bond as a conformational tool in organic and biological chemistry

• Luke Hunter

Beilstein J. Org. Chem. 2010, 6, No. 38, doi:10.3762/bjoc.6.38

• dipole moment caused by the orientation of all four fluorine atoms on the same face of the molecule. Overall, this work illustrates that a basic knowledge of the conformational preferences of multi-vicinal fluoroalkanes can have a valuable bearing on the design of functional materials. Peptides and

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• adopt hydrogen bond stabilised conformations whereas 2,4-trans-THF-L-xylonate oligomers do not. Additionally, a number of structurally related THF aminoacid oligomers were examined by chiroptical spectroscopy to aid interpretation of their conformational preferences. The use of CD, in addition to NMR

Asymmetric synthesis of biaryl atropisomers by dynamic resolution on condensation of biaryl aldehydes with (−)-ephedrine or a proline- derived diamine

• Ann Bracegirdle,
• Jonathan Clayden and
• Lai Wah Lai

Beilstein J. Org. Chem. 2008, 4, No. 47, doi:10.3762/bjoc.4.47

• substrates Previous success with stereocontrol employing ephedrine-derived oxazolidines [15][26][27][34][35] and proline-derived imidazolidines [25][27] prompted us to investigate the thermal stability and conformational preferences of similar products arising from condensation reactions of 2-formylbiaryls

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

• preference extends to 2,3-difluorobutane [2], and we have shown that erythro- and threo-9,10 difluorostearic acids have very different physical properties [3], the origin of which appears to lie in the different conformational preferences associated with the vicinal difluoro- motif for each diastereoisomer

• amorphous material and thus a comparison of solution and solid state structures was not possible for this isomer. Amides of 2,3-difluorosuccinic acid It was an objective of this research to explore the conformational preferences of amides of 2,3-difluorosuccinamides, particularly as we have previously