Chiral Separation of Diastereomeric and Enantiomeric Products Obtained by an Organic Reaction in Aqueous Media between Cyclohexanone and p-nitrobenzaldehyde by HPLC on Chiral Stationary Phase

To understand the intimate essence of the phenomena that occur around us and in us, it is necessary to go down to the atomic and molecular level. From the scale of atoms to the human one, nature is chiral (the term derives from the Greek χείρ, “hand,” that are not superimposable). A chiral chemical compound exists as two isomeric forms, called enantiomers, which are the mirror image of each other and cannot be superimposed on each other. It is important to understand the cause-effect correlations of this asymmetry, which seems to be universal feature of many natural substances; in fact, many drugs, food additives, flavors, cosmetics, agrochemicals, and so on show chirality and surprisingly the biological activity of the two enantiomers is often different (for example one is biologically active, while the other is not active). To separate enanatiomers, an interaction with an entity that is also chiral with the formation of special interactions is required. This work describes the development of the separation method of four diastereoisomers obtained as products (adducts) of an organic reaction between cyclohexanone and benzaldehyde variously substituted in aromatic ring. The chiral separation of the two geometric isomers syn and anti adducts produced by the reaction is obtained by high performance chromatography with a diode detector (HPLC-DAD), using a chiral column and a ternary mixture composed of n-hexane, dichloromethane and ethanol.