Abstract: This invention relates to a process for the synthesis of a non-racemic cyclohexene compound of formula (I) by a Diels-Alder reaction of a compound of formula (II) with a compound of formula (III) wherein R1, R2, R3, R4, R5, R6, R7, R8, R9 and Y have the meanings as defined in the description in the presence of a catalyst comprising at least one m-valent metal cation Mm+ wherein the metal M is selected from Scandium (Sc), Yttrium (Y), Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium 15 (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu), Gallium (Ga) and Indium (In), and m is an integer of 1, 2 or 3, and a chiral ligand of the formula (IV) wherein R10a, R10b, R10c, R10d, R10a?, R10b?, R10c?, R10d?, Z and Z? have the meanings as defined in the description.