Synthesis and labeling of a squaric acid containing PSMA-inhibitor coupled to AAZTA⁵ for versatile labeling with ⁴⁴Sc, ⁶⁴Cu, ⁶⁸Ga and ¹⁷⁷Lu

Highlights: • Synthesis A combination of PSMA inhibitors and AAZTA via sqauric acid is possible, following established syntheses. • Labeling of AAZTA derivatives is possible with ⁴⁴Sc, ⁶⁸Ga and ¹⁷⁷Lu providing good in vitro stability. • Labelling of AAZTA derivatives with ⁶⁴Cu is possible, but provides poor in vitro stability over long time periods. • AAZTA in the form of AAZTA.SA.PSMA is a versatile molecule for easy labeling at room temperature with a variety of nuclides.