Electronic Circular Dichroism

Bari, Lorenzo Di

doi:10.1002/9783527633272.ch9

Cited by 15 publications

(13 citation statements)

References 81 publications

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“…[34,35] Higher-level quantum-mechanical methods such as TDDFT are too computationally demanding because of the molecular size and the large number of conformers to be considered. ZINDO/S-CI calculations were run on 14 low-energy conformers for 2 and nine for 3.…”

Section: Resultsmentioning

confidence: 99%

New Anthracene Derivatives – Structure Elucidation and Antimicrobial Activity

et al. 2012

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Three new anthracene derivatives, which include tetrahydroanthraquinone 1 and two tetrahydroanthraquinone heterodimers 2 and 3, were isolated from Stemphylium globuliferum, together with four known metabolites 4-7. Detailed analysis of the spectroscopic data allowed the unambiguous determination of the structures of 1 and 2 and a revision of the structure of alterporriol C and its atropisomer. Furthermore, alterporriol G, previously obtained as part of a mixture, was isolated in its pure form for the first time and its structure was also revised. The absolute configurations of 1, 2 and 3 were assigned by calculation of their CD spectra, which also allowed the configurational assignment of altersolanol A and the determination of the axial chirality of alterporriols D and E. All isolated compounds were analysed for their antimicrobial and cytotoxic activities. Compounds 1 and 5 inhibited the growth of most pathogenic microorganisms tested, whereas 2, 6 and 7 showed selective inhibition of bacteria but were inactive against fungi. Three new anthracene derivatives and four known metabolites were isolated from the extract of the endophytic Stemphylium globuliferum. The structures were determined by comprehensive NMR spectroscopy and MS, and the absolute configurations by TDDFT and ZINDO methods. All isolated compounds were tested for their cytotoxic and antimicrobial activities

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Section: Resultsmentioning

confidence: 99%

New Anthracene Derivatives – Structure Elucidation and Antimicrobial Activity

et al. 2012

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“…The analysis of the CD spectrum of (+)‐ 1 was based on a so‐called dissection approach, which amounted to considering a model molecule ( 1diss , Fig. ) cut at the C‐10/C‐3′ bond, that is, with the indole group replaced by a hydrogen atom.…”

Section: Resultsmentioning

confidence: 99%

Chaetoglobosin V_b from Endophytic Chaetomium Globosum: Absolute Configuration of Chaetoglobosins

et al. 2012

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One new cytochalasan alkaloid, chaetoglobosin V(b) (1), together with two structurally related known compounds, chaetoglobosin V (2) and chaetoglobosin G (3), was isolated from the ethyl acetate extract of a culture of the endophytic fungus Chaetomium globosum, associated with the leaves of Ginkgo biloba tree. The structures of the isolated compounds were elucidated by spectroscopic methods including 1D and 2D NMR and mass spectrometry. The absolute configuration of chaetoglobosin V(b) (1) was established by means of electronic circular dichroism (CD) spectroscopy, on the basis of the comparison between the CD spectrum of (+)-1 with that calculated with time-dependent density functional theory method for a simplified model. The correlation between compounds 1-3 was demonstrated by a biomimetic transformation of chaetoglobosin G (3) under mild conditions in chaetoglobosins V and V(b) (1 and 2). The isolated metabolites were tested against some phytopathogens.

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“…[27] It is worth recalling here that circular dichroism in general-and definitely ECCD-is a property dependent on the overall molecular stereochemistry and that it is strongly sensitive to conformational issues and not only to absolute configuration. [28] Let us analyze the situation for the free macrocycle, first. One may put forward that if the free ligand is flexible, the extent of coupling within one chromophore and the other is reduced, on account of a manifold of different reciprocal arrangement due to the conformational distribution.…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

“…We can put forward that there is a strong role of exciton coupling between electric dipole transitions, but also other interactions may come into play. [27,28] The aged solution reveals a UV-ECD spectrum which retrieves some of the features of the free macrocycle. In the first place, we can notice that the exciton couplet at 220 nm has recovered much of its original shape and intensity, just as if binaphthol had gained new conformational freedom, with respect to its environment.…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

Reversible Mutarotation in a Macrocyclic Ytterbium Complex

Ballistreri

Gentile

Pappalardo

et al. 2010

Chemistry A European J

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M40 is a four-fold symmetry macrocyclic ligand endowed with axial and central chiral elements, all of R configuration. It promptly binds late lanthanides (Yb(III) and Lu(III) ) yielding a negative helicity, as witnessed by NIR-electronic circular dichroism. In the course of a few hours, a new conformation of the complex takes over, which has opposite helicity and allows for a dynamic free-bound equilibrium. Upon slow solvent evaporation, the original conformation is retrieved and the whole dynamic process can be started again, as in a sandclock, allowing one to envisage applications as a time-marker chiral switch.

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Electronic Circular Dichroism

Cited by 15 publications

References 81 publications

New Anthracene Derivatives – Structure Elucidation and Antimicrobial Activity

New Anthracene Derivatives – Structure Elucidation and Antimicrobial Activity

Chaetoglobosin V_b from Endophytic Chaetomium Globosum: Absolute Configuration of Chaetoglobosins

Reversible Mutarotation in a Macrocyclic Ytterbium Complex

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Electronic Circular Dichroism

Cited by 15 publications

References 81 publications

New Anthracene Derivatives – Structure Elucidation and Antimicrobial Activity

New Anthracene Derivatives – Structure Elucidation and Antimicrobial Activity

Chaetoglobosin Vb from Endophytic Chaetomium Globosum: Absolute Configuration of Chaetoglobosins

Reversible Mutarotation in a Macrocyclic Ytterbium Complex

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Chaetoglobosin V_b from Endophytic Chaetomium Globosum: Absolute Configuration of Chaetoglobosins