Process of separating chiral isomers of chroman compounds and their derivatives and precursors

Process of separating chiral isomers of formula (I-A) or (I-B) or (I-C)

• wherein R1, R3 and R4 are independently from each other hydrogen or methyl groups;
• R2 represents hydrogen or an phenol protection group;
• R5 represents either a linear or branched completely saturated C6-25-alkyl group or a linear or branched C8-25-alkyl group comprising at least one carbon-carbon double bond;
• and wherein * represents the chiral centre of the chiral isomer of formula (I-A) or (I-B) or (I-C);
• comprising the steps
• a) providing a mixture of at least two isomers of formula (I-A) or (I-B) or (I-C);
• b) chromatographic separation of the mixture of isomers of formula (I-A) or (I-B) or (I-C) by means of a chiral phase into desired isomer (I) and residual (I′);
• c) isomerizing the chirality at the centre indicated by * in formula (I-A) or (I-B) or (I-C) of the isomers of the residual (I′) being separated in step b);
• d) adding the isomerized isomers obtained in step c) to a mixture of at least two isomers of formula (I-A) or (I-B) or (I-C) being object of further separation;
• e) collecting the desired isomer (I).