Chiral nickel(II) complexes in the preparation of 11C- and 18F-labelled enantiomerically pure α-amino acids.

Positron emission tomography (PET) utilises positron emitting radiopharmaceuticals in the study of metabolic and physiological processes. FDG-PET is a useful technique for tumour detection; however FDG has disadvantages. The incorporation of labelled amino acids into brain tumours and into some other organs with high physiological consumption of glucose is a superior diagnostic method due to its much higher selectivity compared to FDG. A Ni(II) complex with a Schiff base of BPB and glycine was one of the first glycine synthons used for asymmetric synthesis of carbon-11 and fluorine-18 labelled α-amino acids. A similar complex was employed for routine preparation of [(18)F]FET. Physico-chemical investigations allowed us to design modified complexes with much stronger stereodiscriminative power including stereospecific ones. Chiral nickel complexes are also used for the preparation of tailored amino acids for the incorporation into peptides followed by labelling the peptides with fluorine-18 labelled "click" reagents. This review covers PET applications of Ni(II) complexes of Schiff base of BPB and α-amino acids from 1989 to date.