Separation of diastereoisomers

A process for modifying the relative ratios of the components of a liquid starting mixture of diastereoisomers of formula (I)

• in which the diastereoisomers have at least two asymmetric carbon atoms, n is an integer from 0 to 2, R1, R2, R3 and R4, same or different to each other, are H or C1–C20 hydrocarbon groups, optionally containing heteroatoms, G is a —COOR′, —OR′, —C═OR′, —NR2′, or —PR2′ group, wherein R′ is H or C1–C20 hydrocarbon groups, optionally containing heteroatoms, the process comprising the following steps:
• (i) contacting said liquid starting mixture with a Lewis acid compound, capable of co-ordinating at least one component of the starting mixture, which is used in an amount not enough to co-ordinate the total amount of the diastereoisomeric components of the liquid starting mixture;
• and
• (ii) subjecting the resulting mixture to conditions such that a reaction product, having a molar ratio between its diastereoisomeric components different from the corresponding molar ratio in the said liquid starting mixture, becomes separated from the said liquid mixture;
• wherein step (ii) can be carried out during or after step (i).