Optical rotatory dispersion absolute configuration

Azetidine, 7V-bromo-, 7, 240 Azetidine, AT-r-butyl- N NMR, 7, 11 Azetidine, AT-t-butyl-3-chloro-transannular nucleophilic attack, 7, 25 Azetidine, 3-chloro-isomerization, 7, 42 Azetidine, AT-chloro-, 7, 240 dehydrohalogenation, 7, 275 Azetidine, 7V-chloro-2-methyl-inversion, 7, 7 Azetidine, 3-halo-synthesis, 7, 246 Azetidine, AT-halo-synthesis, 7, 246 Azetidine, AT-hydroxy-synthesis, 7, 271 Azetidine, 2-imino-stability, 7, 256 Azetidine, 2-methoxy-synthesis, 7, 246 Azetidine, 2-methyl-circular dichroism, 7, 239 optical rotatory dispersion, 7, 239 Azetidine, AT-nitroso-deoxygenation, 7, 241 oxidation, 7, 240 synthesis, 7, 246 Azetidine, thioacyl-ring expansion, 7, 241 Azetidine-4-carboxylic acid, 2-oxo-oxidative decarboxylation, 7, 251 Azetidine-2-carboxylic acids absolute configuration, 7, 239 azetidin-2-ones from, 7, 263 synthesis, 7, 246... 

Because configurational information can be derived from optical rotatory dispersion and circular dichroism scans, considerable work has been conducted using these techniques to study the tetracyclines (32). The absolute configuration of CTC was determined using optical rotatory dispersion data (33) Spectral curves are presented in Figures 8 and 9. The circular dichroism spectrum is similar to that presented by Mitscher et al. (34), except that the values differ by a factor of about 1.5. In Table 3, data obtained by Mitscher and in FDA laboratories are compared. 

The optical purity of the phosphonate (123)148 and the absolute configuration of the phosphonium bromide (124)149 have been established. Optical rotatory dispersion and circular dichroism have been used in stereochemical studies of phospholipids150 and adenosine-5 -triphosphate.151... 

In addition to chemical correlations discussed above, several physical methods are now available for the determination of the relative and absolute configurations of chiral sulfur compounds. Among these, NMR, infrared (IR), optical rotatory dispersion (ORD), circular dichroism (CD), and X-ray analysis are the most important. Sections III-B-1 to III-B-5 outline applications of these techniques for establishing the chirality around the sulfur atom. 

Gaffield, W., Circular dichroism, optically rotatory dispersion and absolute configuration of flavanones, 3-hydroxyflavanones and their glycosides. Determination of agyclone chirality in flavanone glycosides, Tetrahedron, 26, 4093, 1970. 

After decarboxylation, enolization in the alternative mode would cause racemization. However, this reasoning does not explain why 199 was racemized. The racemic a-aminoketones were eventually resolved via their bromocamphorsulfonates. Optically pure (—)-indolizidin-l-one (196) was reduced with lithium aluminum hydride to the alcohol, tosylated, and again reduced to (+)-indolizidine [Eq. (28)]. Since indolizidine obtained from R-pipecolic acid [Eq. (29)] was levorotatory, it followed that the absolute configuration of the original ketone was S.254 The optical rotatory dispersion (ORD) curve of the S(-)-ketone showed a strong negative Cotton effect as predicted by the octant rule. 

Optical rotatory dispersion studies on lactones of aldonic acids and other carbohydrate acids were made by Hirst et al.11 and later by Okuda et al.7S The latter workers related the absolute configuration at C-2 of aldono-1,4-lactones to the sign of the Cotton effect. 

Actinidine (26) has been isolated from the roots and rhizomes of Valeriana officinalis L.2S Boschniakine (27) has been found in the seeds of Plantago sempervirens its absolute configuration has been established by optical rotatory dispersion comparisons with other monoterpene bases.26 Venoterpine (28) has been found in Striga hermonteca the stereochemistry is as yet uncertain.27... 

Methoxyquebrachamine (VIII) has the rotation, —103° in dioxane, compared with — 111° found for quebrachamine (I) in the same solvent, and the optical rotatory dispersion (ORD) curves are very similar. It may therefore be deduced that (— )-quebrachamine has the same absolute configuration at position 5 as does aspidospermine. 

For many years no attempt was made to determine the absolute stereochemistry of transition metal complexes, although Kuhn (8) calculated the absolute configuration of (—)n-[Co(C204)3]3- from its anomalous optical rotatory dispersion, using classical coupled oscillator theory. He later (9) extended his theory to other tris-chelated cobalt complexes such as (+)n-[Co(en)3]3+. However, in 1955 Saito (10) showed by anomalous X-ray dispersion that Kuhn s suggested configuration for (+)n-[Co(en)3]3+ was incorrect. 

Gaffield W (1970) Circular Dichroism, Optical Rotatory Dispersion and Absolute Configuration of Flavanones, 3-Hydroxyflavanones and their Glycosides Determination of Agly-cone Chirality in Flavanone Glycosides. Tetrahedron 26 4093... 

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,... 

The helical disposition of the aromatic ligands in the tris complexes confers optical rotatory strength on the ligand transitions [372, 495). This fact may be used to arrive at the absolute configuration of the complex, e.g., (-l-)Ru(phen) + has been shown to exist as a left-handed helix [495). The optical rotatory dispersion of phenanthroline complexes of zinc, cadmium, and mercury has also been studied [419). 

Both antipodes racemize rapidly in solution, although less rapidly than the corresponding trioxalatochromates racemization is complete within 24 hours. Racemization is reported to occur even in the solid state. Isotopic exchange studies have shown only limited parallelism between the mechanisms of oxalate exchange and racemization. Optical rotatory dispersion measurements - have been used to determine the absolute configuration of the trioxalatocobaltate(III) ion. 

D. Gillard, Optical Rotatory Dispersion and Circular Dichroism, in H. A. O. Hill and P. Day, eds.. Physical Methods in Advanced Inorganic Chemistry, Wiley-lnterscience, New York, 1968, pp. 183-185 C. J. Hawkins, Absolute Configuration of Metal Complexes, Wiley-lnterscience, New York, 1971, p. 156. 

Other methods have also been used for determining absolute configuration in a variety of molecules, including optical rotatory dispersion, circular dichroism, " and asymmetric synthesis (see p. 166). Optical rotatory dispersion (ORD) is a measurement of specific rotation, [a], as a function of wavelength. The change of specific rotation [a] or molar rotation [[Pg.160]

Optical rotatory dispersion (ORD) spectra have also been used to assign absolute configiu-ation to these alkaloids. (— )-Tetrahydro-palmatine (XLI) exhibits a negative Cotton effect in the region of 300 mp. and this has been correlated with the representation of its absolute configuration as 14 R on the basis of a comparison with the positive plain dispersion curve shown in this region by (+ )-l,2-diphenylethylamine (XLIX) (97). 

From the optical rotatory dispersion curve of samandarone its absolute configuration, and consequently that of samandarine, can be determined... 

Nishida et al18 proposed the 35-configuration on the basis of their optical rotatory dispersion (ORD) spectra coupled with NMR studies employing a chiral shift reagent. No information was available to assign the absolute configuration at C-11, because the stereocenter at C-ll was separated from the C-3 stereocenter by seven methylene groups. 

Two useful hints were available about the stereochemistry of the natural 90. First, the absolute configuration at C-l of lardolure was assigned as R by the ORD (optical rotatory dispersion) comparison of the natural 90 with (SH-methylheptyl formate. Secondly, Y. Kuwahara observed that his synthetic mixture consisting of all the eight diastereomers of 90 gave seven peaks when analysed by capillary GC, and the peak showing the shortest retention time coincided with that of the natural 90. 

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