Optical rotatory dispersion curves

The optical rotatory dispersion curves of steroidal ketones permit a distinction to be made between the conformations, and assignment of configuration is possible without resorting to chemical methods (see, e.g. ref. 36) which are often tedious. The axial halo ketone rule and, in the more general form, the octant rule summarize this principle and have revealed examples inconsistent with the theory of invariable axial attack in ketone bromination. 2-Methyl-3-ketones have been subjected to a particularly detailed analysis. There are a considerable number of examples where the products isolated from kinetically controlled brominations have the equatorial orientation. These results have been interpreted in terms of direct equatorial attack rather than initial formation of the axial boat form. 

The P configuration at C-6 is based on mechanistic considerations and analysis of optical rotatory dispersion curves. 

Like other phenomena involving interactions between electromagnetic radiation and organic molecules, as in infrared, ultraviolet, and nmr spectroscopy, optical rotatory dispersion curves often are quite sensitive to small changes in structure. As an example, the rotatory dispersion curves for enantiomers of cis- and trcMr-lO-methyl-2-decalones, 16 and 17, are reproduced in Figure 19-7 ... 

This means that the molar extinction coefficients of the two enantiomers (e, and er) are unequal in circularly polarized light. These differences in absorption (e, and er) can be measured as a function of wavelength, and the curves obtained are called circular dichroism curves. They have positive or negative signs (Cotton effect) just as for optical rotatory dispersion curves. 

T. Okuda, S. Harigaya, and A. Kayomoyo, Studies on optical rotatory dispersion of five-member sugar-lactones configuration and signal of an optical rotatory dispersion curve, Chem. Pharm. Bull. (Tokio), 12 (1964) 504-506. 

Figure 4. Optical rotatory dispersion curves as would be...

Baker trans rule or the Hudson isorotation rules have to be taken with care in view of some anomalies.11,38,39 Nuclear magnetic resonance spectra 38 and optical rotatory dispersion curves 38,40,41 have been recently applied to determine the configuration of pyrimidine nucleosides at the anomeric center. 

Palytoxin is a white, amorphous, hydroscopic solid that has not yet been crystallized. It is insoluble in nonpolar solvents such as chlorophorm, ether, and acetone sparingly soluble in methanol and ethanol and soluble in pyridine, dimethyl sulfoxide, and water. The partition coefficient for the distribution of palytoxin between 1-butanol and water is 0.21 at 25°C based on comparison of the absorbance at 263 nm for the two layers. In aqueous solutions, palytoxin foams on agitation, like a steroidal saponin, probably because of its amphipathic nature. The toxin shows no definite melting point and is resistant to heat but chars at 300°C. It is an optically active compound, having a specific rotation of -i-26° 2° in water. The optical rotatory dispersion curve of palytoxin exhibits a positive Cotton effect with [a]25o being -i-700° and [a]2,j being +600° (Moore and Scheuer 1971 Tan and Lau 2000). 

Raney nickel) of the potassium salt of D-xy/o-5-hexulosonic acid oxime produces a mixture of 5-amino-5-deoxy-L-idonic and -D-glu-conic acid in the ratio of 2 1, which is converted into the methyl ester hydrochloride. Upon treatment with alkali, spontaneous cyclization to the pair of 1,5-lactams occurs. 5-Amino-5-deoxy-L-idono-l,5-lactam and 5-amino-5-deoxy-D-glucono-l,5-lactam were separated by recrystallization. The optical rotatory dispersion curves of both compounds were discussed. A new type of lactam, namely, 2-enamino-N,N -bis[(p-methoxycarbonyl)phenyl]-4-(D-gaiacfo-penta-acetoxypentyl)-4-butanelactam was prepared by tbe reaction of 5,6,7,8,9-penta-0-acetyl-3,4-dideoxy-D-ga/ocfo-nonulos- rcns-3-en-l-onic acid with methyl p-aminobenzoate. 

Fig. 2.—Optical Rotatory Dispersion Curves for 5-Amino-5-deoxy-a-i>-xylopyranoses and Their Methyl Glycosides. [Concentrations, 1 mg./ml. in water (left diagram), and...

Reaction Mechanisms. Bailar (2 3) studied the formation of [Co (en) 2003]" from optically active m-[Co(en)2Cl2] and found that products of opposite configurations were obtained under different conditions. He proposed a Walden type inversion for the substitution process. The configurations of the original complex and the products were related using optical rotatory dispersion curves. Dwyer (19) studied these reactions in detail and concluded that the inversion occurs through a trans displacement process involving both Ag+ and OH ... 

Because the Pfeiffer effect is exhibited by tris(l,10-phenanthroline)-nickel(II) ion and d-a-bromocamphor-7r-sulfonate and, because the complex has an absorption band in the visible region, this system was studied using optical rotatory dispersion techniques. The study revealed that the optical rotatory dispersion curves showing Pfeiffer rotation vs. wavelength were very similar to that of the resolved complex (Figures 3 and... 

R = CH2CH2COOCH2C6HS) initiated by hexylamine in dimethylfonnaniide, a homogeneous reaction (Tables 9 and 10) (48). In these tables, it is interesting to note that the a-helical content Xh of the polymer formed, as obtained by the analysis of the optical rotatory dispersion curve, increases throug)iout the reaction, indicatii the incorporation of R antipode into the r t handed helix of the po mer rich in S residues. 

Fig. 2. Optical rotatory dispersion curves of tetrahydropalmatine enantiomers [reproduced from Craig and Roy (98)].

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

Figure 46. A, Absorption curves for the purple membrane sonicated 1 minute (curve b) and the pseudoreference state as defined in equations 84 and 86, curve a. Reproduced, with permission, from [125], B, Circular dichroism spectra of purple membrane. Curve a, suspension of fresh purple membrane preparation sonicated for 1 minute. Curve b, pseudoreference state, 20% triiluoroethanol (TFE)/80% water with 0.4% SDS. This state was defined by equations 84 and 86. Curve c, pseudoreference state optical rotatory dispersion curve plotted on the right-hand ordinate. Dashed curve d, corrected ellipticities using 10" as the...

These chelating agents have frequently been used as probes for the interactions taking place at the catalytic site. Vallee and co-workers (133,232,233,246-248) have utilized the optical rotatory dispersion curves of the complexes, whereas Yonetani (97,120) and Sigman (249) have studied the changes in the absorption spectrum. By the latter method dissociation constants have been measured for a number of binary substrate and inhibitor complexes as well as some ternary inhibitor complexes. The interaction of LADH and a spin-labeled analog of 1,10-phenanthroline has also been studied (141)-Heterocyclic nitrogen bases such as imidazole have been found (244, 60-252) to form both binary complexes with LADH and ternary... 

The addition of hydrogen to the si face of 5 was established by chemical degradation of SH to the 3,4-[4- H)dihydrolactam (6H), shown to have the (5)-configuration at C-4, owing to the correspondence between its optical rotatory dispersion curve and that of authentic 6H. Moreover, this assignment indirectly established that the NAD FMN oxidoreductase from Beneckea harveyi likely... 

Carl Djerassi, have studied this phenomenon in detail. Various theories have been developed which relate these optical rotatory dispersion curves for solutions of macromolecules to their conformations. For example, synthetic long-chain molecules present in solution in a helical form will behave very differently from the molecules present in a random arrangement (Figure 3.7). On the basis of a detailed analysis of the Cotton effect it has been possible to determine what proportion of a protein molecule occurs in the helical form. 

Optical rotatory dispersion curves for poly-Ldysine, in helical and random-coil conformations. The helical form is the z-helix (see p. 133). 

The absolute configuration of vincamine and hence the other eburn-amine alkaloids has been accomplished by showing that the optical rotatory dispersion curve of ( —)-l,l-diethyl-l,2,3,4,6,7,12,12b-octa-hydroindolo[2,3a]quinolizine (XVI) (mp 105°-106°) obtained by a Wolf-Kishner reaction on (— )-eburnamonine was enantiomeric with (-I-)-l,2,3,4-tetrahydroharman (XVII) (24). The i -configuration has to be ascribed to the latter compound because it has been converted into V-carboxyethyl-D-alanine (XVIII) of known absolute configuration (24). This work, with the exception of the Schizozygia alkaloids, establishes the absolute configurations of the eburnamine alkaloids since they have all been interrelated. 

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