Electronic circular dichroism absolute configuration

Bicker W, Kacprzak K, Kwit M, Lammerhofer M, Gawronski J, Lindener W (2009) Assignment of absolute configurations of permethrin and its synthon 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid by electronic circular dichroism, optical rotation, and X-ray crystallography. Tetrahedron Asymmetry 20 1027-1035... 

Optical rotation (OR), optical rotatory dispersion (ORD), electronic circular dichroism (BCD), and vibrational circular dichroism (VCD) provide spectral information nniqne to enantiomers, allowing for the determination of absolute configuration. Recent theoretical developments in DFT, using time-dependent density fnnctional theory (TD-DFT), provide the means for computing OR, ORD, and Similar theoretical development with coupled-cluster theory,... 

Two diastereoisomers of each bi dipeptidato) complexes were separated by anion-exchange chromatography on QAE-Sephadex A-25, and their absolute configurations were determined by PMR, electronic, circular-dichroism spectroscopy. Referring to the stereoselectivity, the workers said that with optically active peptides the formation is stereoselective, but not stereospecific as had earlier been suspected. 

Grkovic T, Ding Y, Li X-C, Webb VL, Ferreira D, Copp BR (2008) Enantiomeric discorhabdin alkaloids and establishment of their absolute configurations using theoretical calculations of electronic circular dichroism spectra. J Org Chem 73 9133-9136... 

Electronic circular dichroism for compounds without a chromophore To determine the absolute configuration of compounds without a chromophore in the accessible spectral region one or more proper groups can be derivatized to obtain an appropriate chromophoric system. The substitution of di-hydroxysteroids with two p-methoxybenzoates can be mentioned as an example. The substitution leads to an inherent dissymmetric chromophore for which the exciton chirality method can be applied. For chiral diols and amino alcohols another interesting possibility does exist. Complexing of these diols and amino alcohols with a transition metal... 

Quantum mechanical computation for electronic circular dichroism and vibrational optical activity With the exception of the exciton chirality method for the development of sector and helicity rules, reference compounds are needed. Their absolute configuration has been usually obtained by X-ray analyses. The progress in numerical techniques of quantum mechanics nowadays allows performing computations of the rotational strength and its sign and, thus, the CD spectra with high reliability for CD... 

One prominent member of this class of natural products is diversonol (185), which was isolated by Turner in 1978 [128]. Its absolute configuration was determined by Krohn et al. [129] using CD spectroscopy and time dependent density functional theory calculations for electronic circular dichroism (TDDFT ECD) calculations. As discussed in Chapter 14.2, Erase et al. [71, 72] published the first enantioselective synthesis of 185 in 2011 using an anionic domino process. 

R81 S.-D. Zhao, L. Shen, D.-Q. Luo and H.-J. Zhu, Progression of Absolute Configuration Determination in Natural Product Chemistry Using Optical Rotation (Dispersion), Matrix Determinant, and Electronic Circular Dichroism Methods , Curr. Org. Chem., 2011, 15, 1843. 

Figure 1 compares TDDFT and experiment for the electronic Circular Dichroism (CD) spectrum of the chiral fullerene Cyg. A total of 240 optically allowed transitions were required to simulate the spectrum. The accuracy is clearly good enough to assign the absolute configuration of Cyg. TDDFT calculations of this size typically take less than a day on low-end personal computers. 

Org. Chem.,69,1948 (2004). Determination of Absolute Configuration Using Concerted Ab Initio DFT Calculations of Electronic Circular Dichroism and Optical Rotation Bicyclo [3.3.1] nonanediones. 

The analogous reaction of 83 with phloroglucinol (1,3,5-trihydroxybenzene) led to the corresponding isomer of type 87 in 10 % yield. The racemic mixture of this compound was resolved by chiral HPLC on Chiralpak ADH stationary phase using propan-2-ol/hexane (2 98) as mobile phase. The absolute configuration of the two separated enantiomers was determined by the comparison of experimentally measured optical rotation dispersion and electronic circular dichroism with DFT calculations of these chiroptical properties [39]. 

Stephens, P.J., McCann, D.M., Devlin, F.J., and Smith, A.B.III (2006) Determination of the absolute configurations of natural products via density fimctional theory calculations of optical rotation, electronic circular dichroism, and vibrational circular didiroism the cytotoxic sesquiterpene natural products quadrone, suberosenone, suherosa-none, and suberosenol A acetate. J. Nat. Prod., 69, 1055-1064. 

The absolute configuration of chiral nonracemic compounds can be established by forming a complex which can bind to the axial position of [Rh2(02CCF3)4] and thus induce circular dichroism within its electronic absorption bands. This method works well for chiral secondary alcohols and monoolefins. For these compounds tentative rules were proposed, which correlate the configuration of the starting materials with the sign of certain Cotton effects of their complexes178. 

Compound Electronic ORir Mr Circular dichroism Absolute configuration Ref. 

---