DOTA tris(phenylmethyl) ester: a new useful synthon for the synthesis of DOTA monoamides containing acid-labile bonds.

The synthesis of DOTA tris(phenylmethyl) ester 2, a new monoreactive derivative of DOTA, is described. This versatile synthon can be easily coupled to compounds bearing an amino group and then deprotected to DOTA monoamide under mild and neutral conditions by catalytic hydrogenolysis. Accordingly, compound 2 has been used in the synthesis of a DOTA monoamide gadolinium complex containing two palmitic esters, which is a component of mixed micelles as MRI contrast agents.