NO CARRIER ADDED ELECTROPHILIC RADIOIODINATION OF L-ALPHA-METHYLTYROSINE VIA DIFFERENT OXIDIZING-AGENTS

L-3-[I-123] iodo-alpha-methyltyrosine has been reported to have a high affinity for a transport system in the blood-brain-barrier (BBB). Syn thesis of L-3-[I-123/131] iodo-alpha-methyltyrosine was performed by d irect electrophilic iodination starting with no carrier added (n.c.a) I-131 or I-123 in the presence of oxidizing agent. Different oxidizing agents have been tested and the different factors affecting,the radio chemical yield of L-3-[I-123] iodo-alpha-methyltyrosine have been inve stigated. A method of pharmaceutical preparation of L-3-[I-123] iodo-a lpha-methyltyrosine ready for medical applications has been described. Among the oxidizing agents tested, iodogen in phosphate buffer at pH 7 seems to be the best which gives high radiochemical yield (85%) with in 5 minute reaction lime at room temperature in the presence of small amount KI (0.001 mu g) as a carrier. Tile radioactive impurities and side chlorinated by-product which have been found in case of iodinatio n by chloramine-T (CAT).KIO3 and H2O2 methods disappear in case of iod ogen method. Tile labelled product was separated and purified by radio high pressure liquid chromatography (HPLC) using methanol : water: ac etic acid (20 : 80 : 1) as eluant at a flow rate 1.0 ml/min. According to the signals of the detectors tile fractions of L-3-[I-123] iodo-al pha-methyltyrosine were collected, evaporated to complete dryness and the residue dissolved in isotonic phosphate buffer pH 7.4. The product was sterilized by passing through 0.22 mu m millipore filler and the radiopharmaceutical was now ready for nuclear medical application.