188. Bestimmung des Chiralitaetssinns der enantiomeren 2,6-Adamantandiole

Article abstract of DOI:10.1002/hlca.19850680702

The enantiomers of 2,6-adamantanediol (1) are resolved via the diastereoisomeric camphanoates.The (2R,6R)-chirality sense for (-)-1 and (2S,6S) for (+)-1 was determined by chemical correlation with (-)-(1R,5R)-bicyclo<3.3.1>nonan-2,6-dion((1R,5R)-3) of known absolute configuration in the following way: alkylation of the bis(pyrrolidine enamine) of (-)-(1R,5R)-3 with CD2I2 and hydrolysis of the product gives the enantiomer 4 of (4,4-D2)-2,6-adamantanedione.Reduction of 4 with LiAlH4 leads to one enantiomer (Scheme 2) of each of the three diols 5-7 of known absolute configuration.The three diols are themselves configurational isomers due to the presence of the CD2 group, but correspond otherwise entirely to the enantiomeric diols 1.Accordingly, they can also be separated by means of their diastereoisomeric camphanoates to give the diols 5/6 and 7.These samples are easily distinguished and identified by their characteristic 1H-NMR spectra (cf.Fig. 2.).This allows to identify the (2R,6R)- and (2S,6S)-enantiomer of 1 on the basis of their behaviour in the resolution experiment analogous to that of the diols 5/6 and 7, respectively.The diol (-)-1 must have the (2R,6R)-configuration because it forms, like the diols 5/6, with (-)-camphanic acid the diastereoisomeric ester less soluble in benzene.The diol (+)-1 has (2S,6S)-configuration, because it forms, like 7, with (+)-camphanic acid the diastereoisomeric ester less soluble in benzene.The bis(4-methoxybenzoate) of (-)-(2R,6R)-1 shows chiroptical properties which are in accordance with Nakanishi's rule for two chromophores having coupled electric dipol transition moments arranged with a left handed torsion angle.