Optical Rotatory and Circular Dichroic Scattering

Instrument for determining the polarization state of reflected and transmitted light

Density Functional Theory (DFT) calculations of optical rotation (OR) and vibrational circular dichroism (VCD) have been used to assign the absolute configuration (AC) of a recently prepared (3-phenyloxirane-2,2-diyl)bis(phenylmethanone), 3, by asymmetric epoxidation of the corresponding 2-arylidene-1,3-diketone. The experimental OR at 589.3 nm and the VCD spectrum of the (+)- and (-)-enantiomer of 3 have been measured. The conformationally-averaged OR value and VCD spectrum of (R)-3 were calculated at B3LYP/6-311G(2d,2p) level of theory. Both approaches provide the same absolute configuration of the stereogenic carbon, i.e. the AC of (+)-3 is (R)-3, thus affording a confident assignment. Only two conformational isomers of 3 have been predicted to be populated at ambient temperature. Their presence is directly observed in the VCD spectrum.

From whole plants of Bulbocodium vernum L. the flavone luteoline (I) and the alkaloids colchicine (II), N‐formyl‐N‐deacetylcolchicine (III), 3‐demethylcolchicine (V), (+)‐bulbocodine (IX) and (−)‐kreysigine (XI) were isolated in crystals. The presence of 2‐demethylcolchicine (IV), ß‐ (VII) and γ‐lumicolchicine (VIII), demecolcine (VI) and five not identified alkaloids was demonstrated by thin‐layer chromatography. On the basis of ultraviolet, infrared and mass spectra, PMR.‐analysis (Overhauser effect), and circular dichroism, the (6a‐R, 8a‐S)homo‐proaporphine structure IX, with one methoxy group at C‐2, has been assigned to (+)‐bulbocodine. The (6a‐R)‐structure (XI) was deduced for (−)‐kreysigine by comparing its optical rotation and circular dichroism which the values of (−)‐multifloramine (X), the structure of which is known.

Optical rotatory dispersion and circular dichroism properties of yeast mitochondrial DNA's

Abstract

The optical properties of a planar metamaterial with gammadion-shaped chiral symmetry breaking holes array have been investigated both theoretically and experimentally. The results indicate that the introduction of the chiral symmetry breaking causes the split of the transmission peak and exerts large influence on the optical rotation and circular dichroism. Our metamaterials might have potential applications in future design of plasmonic devices.

During the past decade there has been a considerable resurgence of interest in the optical rotatory dispersion and circular dichroism of coordination compounds.1 In addition, there also has been a considerable renewal of interest in the Pfeiffer effect during this same period of time.2-8 This coincidental renewal of interest in these fields is most fortunate, because it is possible to apply optical rotatory dispersion and circular dichroism techniques to the study of the Pfeiffer effect with fruitful results (vide infra).

An analysis of optical rotatory dispersion and circular dichroism of RNA is described which leads to an estimate of the degree of base pairing. By the use of new standards for the double‐helical parts of the molecule, based on data for two‐stranded viral RNA species, a good fit between calculated and observed curves can be achieved. Where data are available the results of analyses of optical rotatory dispersion and circular dichroism in general show satisfactory consistency.

More than 40 years ago, Kurt Mislow synthesized restrained biphenyl derivatives, classically resolved them and correlated their absolute configuration with the sign of the Cotton effect. We have encountered biphenyl dyes in mixed crystals and crystalline tissues that were presumably resolved by interaction with chiral crystal facets or by adsorption to biopolymers. Understanding association mechanisms required that we likewise determine the absolute configuration, but inside organized media which traditionally do not reveal optical rotation or circular dichroism because of the dominance of linear anisotropies. We therefore recently invented the first circular extinction imaging microscope that can detect circular dichroism in low‐symmetry media, and also a new effect in crystal optics that we call anomalous circular extinction. Here, we show what information can be obtained from dyed, organized substances containing biphenyl derivatives by exploiting this new tool. Copyright © 2004 John Wiley & Sons, Ltd.

Chirality transfer, induction, and circularly polarized luminescence (CPL) using supramolecular hosts, such as macrocycles and cages, have been explored for wide-ranging applications in chiral reco...

Liquid crystalline, rheological and thermal properties of konjac glucomannan

Studies on the conformational transformations of l-arginine molecule in aqueous solution with temperature changing by circular dichroism spectroscopy and optical rotations

The dried roots of Peucedanum praeruptorum Dunn, Baihuaqianhu, is well known traditional Chinese medicine. It has been used as anti-asthma, antitussive and as a remedy for angina. Recent pharmacological studies showed that the extract of P. praeruptorum has various beneficial pharmacological activities. Chromatographic separation of a 70% EtOH extract of roots of P. praeruptorum led to the isolation of a new angular-type pyranocoumarin, along with fifteen known compounds including twelve pyranocoumarins, two furanocoumarins, and a polyacetylene. The structures of all compounds were determined on the basis of 1D and 2D NMR techniques (COSY, NOESY, HSQC, HMBC) in association with HR-ESI-MS data analysis. Their stereochemistry were determined by optical rotation and circular dichroism studies. All of the isolates were evaluated for their protective activity against chemotherapy-induced myelosuppression using ex vivo hematopoietic CFC assay system. Four compounds isolated from P. praeruptorum showed protective effects. In this study, we report the isolation and structural elucidation, and biological activities of these compounds from the roots of P. praeruptorum.

Enantiomeric resolution of albendazole sulfoxide by semipreparative HPLC and in vitro study of growth inhibitory effects on human cancer cell lines

Molecular origins of acetan solution properties