was added dropwise the resulting solution was heated at 50 u00b0 c for 6 h the solvent was evaporated to give the title compound 3 6 g 3 2 mmol yield 87 palmitoyl chloride 29 8 g 108 4 mmol commercial product was added dropwise in 30 min to a solution of diethanolamine hydrochloride 7 g 49 4 mmol commercial product in dmf 100 ml after standing for 1 5 h a white solid crystallized meoh 350 ml was added and the reaction mixture heated to reflux after cooling to room temperature the recrystallized product was filtered to give as a white solid hexadecanoic acid iminodi 2 1 ethanediyl ester hydrochloride 15 g 24 2 mmol yield 49 k f 0 4 the 13 c nmr ms and ir spectra were consistent with the structure a 50 solution of 1 propanephosphonic acid cyclic anhydride 14 4 g 22 6 mmol in etoac commercial product was added to a solution of 1 4 7 10 tetraazacyclododecane 1 4 7 10 tetraacetic acid tris phenyl methyl ester 15 g 22 2 mmol prepared according to step e3 of example 17 hexadecanoic acid iminodi 2 1 ethanediyl ester hydrochloride 14 g 22 6 mmol and et 3 n 6 5 ml 46 6 mmol in ch 2 cl 2 200 ml the reaction mixture was stirred at room temperature.