Optically active diesters of fumaric acid

摘要

Optically active fumaric acid diesters of the formula I <IMAGE> in which R<1> and R<4> denote hydrogen or an optionally substituted alkyl, cycloalkyl, aralkyl or aryl group; R<2> and R<3> denote an optionally substituted alkyl, cycloalkyl, aralkyl or aryl group or the radical -CO2R<5>, where R<5> stands for hydrogen or a C1-C4-alkyl radical; or R<1> is linked with R<2> and/or R<3> is linked with R<4> to give a 5- or 6-membered, optionally alkyl-substituted heterocycle which can carry a further carbonyl group in the adjacent position to X or Y; X or Y stands for oxygen or the radical -NR<1> and C<*> denotes a centre of asymmetry of R or S absolute configuration and the preparation of the diesters I and their use as dienophiles in asymmetric Diels-Alder reactions.