Biocatalytic procedure for obtaining all four diastereoisomers of 1-(1-hydroxyethyl)-3-ethylferrocene: synthons for chiral 1,3-disubstituted ferrocenes

Lipase from Candida antarctica has been successfully used to realise the selective esterification of the four 1-(1-hydroxyethyl)- 3-ethylferrocene isomers, possessing central/planar chirality. In this reaction, the lipase recognises only the two isomers possessing an (R)-configuration, independently from planar chirality. This allows us to split the mixture into two couples of diastereoisomers, namely the (Sp,Rc)-/(Rp,Rc)- and (Rp,Sc)-/(Sp,Sc)-isomers, conveniently separated in the single constituents by crystallisation from hexane.