Structural Studies by Exciton Coupled Circular Dichroism over a Large Distance:  Porphyrin Derivatives of Steroids, Dimeric Steroids, and Brevetoxin B

Matile, Stefan; Berova, Nina; Nakanishi, Koji; Fleischhauer, Jörg; Woody, Robert W.

doi:10.1021/ja960126p

Cited by 229 publications

(240 citation statements)

References 57 publications

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“…Furthermore, the nonequivalent interaction with antipodes as a consequence of the chiral recognition ability allowed 60 to be used as a chiral shift reagent. A more rigid structural motif on the basis of a steroidal skeleton was used to connect two porphyrin moieties in the bis-porphyrins, 61-68 ( Figure 18) [55]. This type of linkage resulted in a considerably stronger chiroptical outcome, with the CD amplitude being as high as +675 cm…”

Section: Achiral Porphyrinoids With Chiral Linkagementioning

confidence: 99%

Supramolecular Chirality in Porphyrin Chemistry

Borovkov

2014

Symmetry

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Supramolecular chirality, being an intelligent combination of supramolecular chemistry and chiral science, plays a decisive role in the functioning of various natural assemblies and has attracted much attention from the scientific community, due to different applications in modern technologies, medicine, pharmacology, catalysis and biomimetic research. Porphyrin molecules are of particular interest to study this phenomenon owing to their unique spectral, physico-chemical and synthetic properties. This review highlights the most important types of chiral porphyrin structures by using the best-suited representative examples, which are frequently used in the area of supramolecular chirality.

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Section: Achiral Porphyrinoids With Chiral Linkagementioning

confidence: 99%

Supramolecular Chirality in Porphyrin Chemistry

Borovkov

2014

Symmetry

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“…43 These chromophores providing powerful absorption (q 419 = 350,000) allowed measurements of exciton CD spectra for cases 44 when the interacting chromophores were separated by a distance of 50 Å . The q max value for carotenoids is around 100,000, so according to theory, 15 about 10 times smaller A values may be expected for identical distance and orientation.…”

Section: Carotenoid Aggregatesmentioning

confidence: 99%

Supramolecular exciton chirality of carotenoid aggregates

et al. 2003

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The conventional organic chemistry concept of chirality relates to single molecules. This article deals with cases in which exciton chirality is generated by the interaction of associated carotenoids. The handed property responsible for exciton signals in these systems is due to the alignment of neighboring molecules held together by secondary chemical forces. Their mutual positions are characterized by the overlay angle. Experimental manifestation is obtained by spectroscopic studies on carotenoid aggregates. Compared to molecular spectra, both UV/visible and circular dichroism spectroscopic observations reveal modified absorption bands and induced Cotton effects of opposite sign (exciton couplets), respectively. A new term, "supramolecular exciton chirality," is suggested for these phenomena, allowing the detection of weak chemical interactions not readily accessible for experimental studies, although highly important in the mechanism of biological processes.

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“…Porphyrins as extremely powerful chromophores for exciton coupled CD.13j 14 In exciton coupled CD, in most cases, acylating chromophores are introduced into the substrate, and the sign of split CD resulting from the coupling between the chromophores are used to determine the absolute sense of twist. This is a very versatile method but the extent of its potentiality has yet to be explored, particularly in conformational studies of large molecules exemplified by biopolymers.…”

Section: Sphingosines and Dihydrosphingosines12mentioning

confidence: 99%

Solving challenging bioorganic problems by exciton coupled CD

Berova¹,

Borhan²,

Jie³

et al. 1998

Pure and Applied Chemistry

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-Determination of molecular chirality is becoming increasingly important due to the sophistication in mode of action studies of biological reactions and the importance of chiral drugs. The exciton coupled CD, based on through space coupling, is a versatile microscale method with superb sensitivity that can be applied to a variety of problems including biopolymers and clusters in lipids. Applications of the exciton coupled CD method to the following problems exemplify its versatility. Quaternary ammonium salts as chromophores for exciton-coupled CD.1'Exciton coupled circular dichroism is a nonempirical submicrogram scale method for determining absolute configurations and conformations of organic molecules in solution based on the interactions of chromophores which are preexisting in the substrate and/or introduced through derivatizations such as 0-or N-acylation.213 However, the method could not be applied to one major group, i.e., tertiary amines which comprise numerous natural products, particularly alkaloids, and synthetic drugs that exhibit conspicuous biological activities. We have succeeded in extending the CD method to quinuclidines (tertiary amines) through quaternary ammonium salt formation, and have applied this new procedure to the important class of hypocholesterolemic quinuclidines. Of the three conformers conceivable for the salt (l), the conformer shown determines the sign of the split Cotton effect (CE). When the phenylbenzyl group is in the north east sector the transition moments ,of the two chromophores are close to being parallel, hence the chirality is negligible; when it is in the north west sector, the distance between the two chromophores is more remote than that depicted, hence the resulting positive bisignate CD will be of smaller amplitude. OMe Acyclic 1,3-polyols with a 1,2-diol terminal.4Acyclic 1,3-polyols are widely distributed in nature. Particularly 1,2,4-triols are present in numerous antifungal polyene macrolides in various masked forms. Although over 200 polyene macrolides are known, the structures of only about 40 have been determined, while those for which the full stereochemistry has been elucidated are less than ten. In order to develop a general chiroptical method for structure determination of acyclic 1,3-polyols, we have combined a divergent synthetic approach with CD to prepare all possible stereoisomers of 1,2,4-triols, 1,2,4,6-tetrols and 1,2,4,6,8-pentols. The current set of reference polyols should be useful for setting up reference CD libraries and for model studies leading to a general method for configurational assignment of acyclic polyols. CD curves of 1,2-diols, 1,2,4-triols, and 1,2,4,6-tetrols with differing stereochemistries have been published earlier.5 3. Synthesis of cyclic mixed polyols6 and acyclic pentol structure of two hopanoids. 7 The synthesis of all eight configurational isomers of acyclic 1,2,3,4,6-pentols belonging to the 2R enantiomeric series has been carried out, and the side-chain configurations of two bacteriohopanoids (2) and (3)...

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Structural Studies by Exciton Coupled Circular Dichroism over a Large Distance: Porphyrin Derivatives of Steroids, Dimeric Steroids, and Brevetoxin B

Cited by 229 publications

References 57 publications

Supramolecular Chirality in Porphyrin Chemistry

Supramolecular Chirality in Porphyrin Chemistry

Supramolecular exciton chirality of carotenoid aggregates

Solving challenging bioorganic problems by exciton coupled CD

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