Enantiopure spiro[3.3]heptane-2,6-dicarboxylic acid.

Using chiral HPLC and 13C NMR analyses, the optical purity of (+)-spiro[3.3]heptane-2,6-dicarboxylic acid (1) obtained by the known diastereomer method with brucine was first clarified to be 90% e.e., which was conventionally considered to be 100% e.e. Among the ester derivatives synthesized, dicinnamyl spiro[3.3]heptane-2,6-dicarboxylate (2) was found to show high optical separation ability on the chiral HPLC with cellulose phenyl carbamate stationary phase eluting with hexane/2-propanol (10/1, v/v) at a flow rate of 0.4 ml/min at 35 degrees C (separation factor, a, 1.14), and the isolated optically pure (+)- and (-)-2 show [alpha]D26 of + 1.84 degrees (c = 1.74, CHCl3) and -1.84 degrees (c = 1.74, CHCl3), respectively. Acidic hydrolysis of optically pure (+)-/(-)-2 without racemization yielded optically pure (+)-/(-)-1, exhibiting [phi]405(270 = + 21.1 degrees ([phi]D27 = +9.1 degrees) (c = 5.33, acetone) and [phi]405(27) = -21.1 degrees ([phi]D27 -9.1 degrees) (c = 5.32, acetone), respectively.