CD-Spectroscopic Investigations for the Determination of the Absolute Configuration of α-Alkylated 1,4-CycIohexanedione Derivatives

Abstract

The absolute configuration of the conformationally flexible six membered ring system 2-methyl- and 2,6-dimethyl-l,4-cyclohexanedione monoethylene acetal was determined by comparison of measured and calculated CD spectra. The rotational strengths were calculated by means of the CNDO/S-method assuming R at the stereogenic center. The results were compared with the predictions made by the octant rule. The enantiomerically pure material was synthesized via the corresponding SAMP- and RAMP-hydrazones.

Absolute Configuration in 4-Alkyl- and 4-Aryl-3,4-dihydro-2(1H)-pyrimidones: A Combined Theoretical and Experimental Investigation

“…11,15 As an alternative to experimental methods, the calculation of CD spectra of chiral moleculesseither by highlevel quantum-chemical methods or semiempirical proceduresshas become increasingly important as a means to establish absolute configuration. [16][17][18][19][20][21][22] Herein we report a detailed analysis of the CD spectra of 4-aryl-and 4-alkyl-DHPMs (see Chart 1 for structures) and describe computational methods that facilitate the analysis of the CD data and the assignment of absolute configuration in this series of compounds. The results obtained thereby are corroborated by X-ray structure determination of the diastereomeric derivative 6.…”