O,O'-Di-p-toluoyl-(2R,3R)-tartaric acid as supramolecular resolving agent

O,O'-di-p-toluoyl-(2R,3R)-tartaric acid (DPTTA) was investigated as supramolecular complex (SMC) forming resolving agent with three racemic alcohols (menthol, 4-methyl-2-pentanol, trans-2-iodo-cyclohexanol) by preparative scale experiments and thermoanalytical measurements. Despite the very small structural difference (two methyl groups) between the O,O'-dibenzoyl-(2R,3R)-tartaric acid (DBTA) and DPTTA, their SMC forming properties with water and racemic alcohols is very different. While DBTA forms SMC with all the three investigated alcohols, DPTTA forms SMC only with trans-2-iodo-cyclohexanol. DPTTA binds the guest compound less strongly and the stoichiometry of the SMC is also different. The weaker interactions resulted in less effective optical resolutions. The results of these investigations remind us, that in optical resolutions during the chiral discrimination process the weaker interactions have a determining role, since DBTA and DPTTA have the possibility to form the same strong (O-H···O and N-H···O) hydrogen bond network.