Absolute chirality

Kanemasa et al.63 reported that cationic aqua complexes prepared from the /ram-chelating tridentate ligand (i ,f )-dibenzofuran-4,6-diyl-2,2,-Mv(4-phcnyloxazolinc) (DBFOX/Ph) and various metal(II) perchlorates are effective catalysts that induce absolute chiral control in the Diels-Alder reactions of 3-alkenoyl-2-oxazolidinone dienophiles (Eq. 12.20). The nickel(II), cobalt(II), copper(II), and zinc(II) complexes are effective in the presence of six equivalents of water for cobalt and nickel and three equivalents of water for copper and zinc. 

Because the time scale of the Raman scattering event ( 3.3 x 10-14s for a vibration with wavenumber shift 1000 cm-1 excited in the visible) is much shorter than that of the fastest conformational fluctuations in biomolecules, the ROA spectrum is a superposition of snapshot spectra from all the distinct chiral conformers present in the sample. Together with the dependence of ROA on chirality, this leads to an enhanced sensitivity to the dynamic aspects of biomolecular structure. The two-group model provides a qualitative explanation since it predicts ROA intensities that depend on absolute chirality in the form of a sin x dependence... 

This discussion brings out an important principle that will reappear time and again in this chapter. If we can assign the absolute direction of the hand vis-a-vis the polar axis b (Figure 2), that is, establish whether the wrist or the fingers of the hand point up, then the absolute chirality of the hand is fixed as well. This determination of absolute polarity can be achieved in several ways other than anomalous scattering of X-rays or neutrons, for example, by an external means such as a solvent, a chemical reagent, or a physical measurement (e.g.,... 

Oil), and of S at (Oll)and(OTT). According to calculated surface binding energies, (/ )-thr may easily be adsorbed only on faces (Oil) and (Oil) and, by symmetry, (S)-thr only on (Oil) and (Oil) indeed, threonine is better bound than even the substrate serine by 3 keal/mol (78). These results fix the absolute chirality of the resolved threonine. 

Fig. 9.6 Human versus machine-readable chemical structure representations. Names based on the depicted structures were interpreted using ACDName [22]. The cross up/down wedge error (middle) causes errors in assigning the absolute chirality.

Chirality — especially together with the description (R) or (5) — will be used in this survey in the sense of absolute chirality and absolute configuration , respectively (see ilso Ref.211 and Sect. 2.9.). 

Absolute chiralities and chiroptical properties of metacyclophanes will be discussed in Section 2.9. 

Based on the CD-spectra of various optically active carbophanes, a sector rule for the correlation of the sign of the 1Lb-Cotton effect of the benzene chromophore with the absolute chiralities of these phanes (as well as for chiral dihydro-9,10-ethano-anthracenes) has been proposed 63). 

Lopinski, G. P., Moffatt, D. J., Wayner, D. D. and Wolkow, R. A. Determination of the absolute chirality of individual adsorbed molecules using the scanning tunnelling microscope. Nature 392, 909 (1998). 

Kajitani T, Masu H, Kohmoto S, Yamamoto M, Yamaguchi K, Kishikawa K (2005) Generation of a chiral mesophase by achiral molecules absolute chiral induction in the smectic C phase of 4-octyloxyphenyl 4-octyloxybenzoate. J Am Chem Soc 127 1124-1125... 

The sea hare Dolabella auricularia was recorded to exhibit exceptionally potent biological properties, which were known to certain ancient Greeks and Romans. The most important antineoplastic constituent of D. auricularia was dolastatin 10 (362) (283), a linear pentapeptide that was reported to be the most potent antineoplastic substance known to date. The absolute configuration of362 was ascertained by total synthesis (284). Synthetic studies revealed that the initial structure (285) proposed for dolastatin 3 was incorrect (286-291). The structure of dolastatin 3 was reassigned as 363, and its absolute chirality was established by synthesis (292). The minimum energy conformation of 363 in solution was estab-... 

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