A solution containing 0.26 mg of 3-aminopropane-1,2-diol in 6 μl of water is prepared. The pH is adjusted to 6 with HCl. 0.5 mg of gallium complex of 2-[4,7-bis(1,4-dicarboxybutyl]-1,4,7,10-tetraazacyclododec-1-yl]hexanoic acid are added to the above solution. The pH is again adjusted before adding 0.071 mg of sulfo-NHS and 0.062 mg of EDCI. The pH is checked and adjusted to 6 with 2N NaOH. After an overnight period at AT, the reaction medium is concentrated to approximately 2 ml and then precipitated from 10 ml of ethanol. The solid is filtered off, washed with ethanol and diethyl ether, and then purified on silanized silica RP2, elution being carried out with water only. 0.2 mg of product is obtained.
