Synthesis and characterization of diastereoisomerically pure tetracyclo[6.2.1.1(3,6).0(2,7)]dodec-9-ene-4-carboxylic acid derivatives

The synthesis and detailed NMR analysis of diastereoisomerically pure sampl es of 4-methyltetracyclo[6.2.1.1(3.6).0(2.7)]dodec-9-ene-4-carboxylic acid (2), tetracyclo[6.2.1.1(3.6).0(2.7)]dodec-9-ene-4-carboxylic acid (6) and t heir tert-butyl esters are reported. Mixtures containing two isomers of the methyl caters of these compounds were obtained by a twofold, sequential Di els-Alder reaction between cyclopentadiene, and methyl methacrylate or meth yl acrylate, respectively. Pure diastereoisomers of the acids were prepared by selective hydrolysis of their methyl esters.