Patent ID: 6992184

Claim:
A method for the synthesis of a ligand having the structure: wherein: B 1 , B 3 and B 4 each represent a bridging group having zero, one two or three carbon containing nodes for substitution, and B 2 represents a bridging group having at least one carbon containing node for substitution, each said node containing a C(R), C(R 1 ) (R 2 ) or C(R) 2 , each R substituent is the same is the same or different from the remaining R substituents and (i) is selected from the group consisting of alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, alkynyl, alkylaryl, halogen, alkoxy, phenoxy and combinations thereof, or (ii) form a substituted or unsubstituted benzene ring of which two carbons on the ring form nodes in the B-unit, said method comprising the steps listed below in the order given a) protecting the amino group of an amino acid comprising HOOC—B 3 —CRR—NH 2 and/or HOOC—B 4 —CRR—NH 2 , b) activating the carbonyl group of said amino acid, c) reacting the carbonyl-activated amino acid with a diamine H 2 N—B 2 —NH 2 to form a diamide diamine, d) deprotecting said protected amino groups, and, e) reacting the de-protected diamide diamine with an activated di-carbonyl compound to form a tetra-amine macrocycle.