Optisch aktive aromatische Spirane, 13. Mitt.

Abstract

Several optically active title compounds were obtained from the 4′-acetyl-4-carboxylic acid2 or the 4,4′-diacetyl derivative4. (−)-2 was accessible by optical resolutionvia its (−)-α-phenethylamine salts, (+)- and (−)-4 as well as the enantiomeric methylesters3 (of2) were obtained by chromatography on triacetylcellulose in ethanol. The enantiomeric purities were established either from the chromatographic results or from the¹H-NMR spectra of the phenethyl-amine saltes (via the diastereotopic acetyl protons).

The chirality (−)-(2R) was deduced for all new compounds from a chemical correlation between (−)-2 and (−)-4 and on the basis of the CD spectra of the latter and of (−)-(2R)-17 of known absolute configuration.

From the molar rotations of these 4,4′-disubstituted 2,2′-spirobiindanes (empirical) ligand parameters λ were determined which for some cases gave good results in the calculation of the rotations (using the “shortened Ansatz”). These results are briefly discussed especially in comparison with 5,5′-disubstituted 2,2′-spirobiindanes.