Determination of the Absolute Configuration and Enantiomeric Purity of Allylic and Acetylenic Alcohols

Article abstract of DOI:10.1246/bcsj.64.3390

The relative magnitude of steric bulk of saturated vs. unsaturated substituents in the title compounds has been estimated by a lanthanoid induced shift (LIS) study of these (R)-(+)-α-methoxy-α-(trifluoromethyl)phenylacetate esters <(R)-(+)-MTPA esters> by 1H NMR spectroscopy: CH2=C(Me)- > Pentyl > n-Pr > Et = CH2=CH- > Me > Ethynyl; Ph > Cyclohexyl.These results allow the assignment of the absolute configurations of both cyclic and acyclic unsaturated alcohols.Furthermore, the relative intensity of well-separated OMe signals for those diastereomeric MTPA esters can be used for the determination of the percent ee of the original alcohols.