- 181 - (2) exchange on the amino derivative, followed by transformation of the amino function into the azido group by reaction with sodium azide. The result of the synthesis was a compound with a specific activity of 9.2 Ci/mmol. To obtain the tritiated azido-QNB, we first iodinated the amino compound, then obtained the 3,5-ditritio related derivative by catalytic tritiodeiodination. The last step was the transformation t6 the azido compound, as was done for the azido-NMPB. The specific activity obtained was 21 Ci/mmol. REFERENCES: 1. Flanagan, S. D. and Storni, A., Brain Res., 168, 261 (1979) 2. Buchman, 0., Pri-Bar, I. and Shimoni, M., J. Label. Compounds Radiopharm., 14, 155 (1978) TRITIATION OF IPRINDOLE AT HIGH SPECIFIC ACTIVITY 0. Buchman, M. Shimoni, A. Cohen, Y. Hagag and J. Azran Iprindole, or 5-{(3-dimethylamino)-propyl}-6,7,8,9,10,ll- hexahydro-5H-cyclooct(b)indole, is a tricyclic antidepressant structurally formed by the linkage of cyclooctane to the double bond of the pyrrole ring from indole. Attempts to tritiate this compound by generally labeling did not succeed. The presence of the catalyst required for this isotopic exchange also saturates the double bond rapidly and completely with tritium. A simple alternative way to synthesize the brominated precursor, starting from iprindole, also failed. In indole-like structured mole­ cules, the direct bromination is not easily performed and it (2) occurs preferentially in position 3 of the pyrrole ring . This position is, of course, not available in iprindole. We therefore synthesized 2-bromoiprindole. The first step was the condensation of 3-bromophenyl hydrazine with cyclooctanone, using a procedure for synthesis of iprindole (3) . The next two step proceeding with the linkage of the aliphatic moiety to the nitrogen (A) atom, were also adapted from the literature . The resulting bromoiprindole was labeled by catalytic tritiodebromination in - 182 - alkaline conditions. Tritiated iprindole was separated and puri­ fied on precoated silica-gel plates. The specific activity obtained was 10.8 Ci/mmol. REFERENCES: 1. Buchman, 0., Pri-Bar, I. and Shimoni, M., J. Label. Compounds Radiopharm., 14_, 155 (1978) 2. Piers, K., Meimarogl, C, Jardine, R. V. and Brown, R. K., Can. J. Chem., 41, 2399 (1963) 3. Rogers, C. U. and Corson, B. B., J. Amer. Chem. Soc, j>9_, 2910 (1947) 4. Bourquin, J. P., Schwarb, G-, Gamboni, G., Fischer, R., Ruesch, L., Guldimann, S., Theus, V., Schenker, E. and Renz, J., Helv. Chim. Acta, 41, 1072 (1958) TRITIATION OF TRIMEPRAZINE M. Shimoni, J. Azran, A. Cohen, Y. Hagag and 0. Buchman Trimeprazine is a phenothiazine derivative similar to those which were previously tritiated with success by catalytic tritiodebromina- tion . The same tritiation procedure, when applied to trimeprazine, provided a mixture of decomposition products. This result was un­ expected since, in the case of levomepromazine and ethymemazine, which are molecules with the same aliphatic moiety, the tritiations were successful and these purified products were obtained with specific activities of, respectively, 17.3 Ci/mmol and 11.5 Ci/mmol. Further attempts to obtain a labeled molecule were disappointing. The only (2) positive result was reached by nonspecific labeling with PdO which enabled us to obtain trimeprazine with a specific activity of 3.4 Ci/ mmol. By comparison, the same labeling procedure provided levomepro­ mazine at 0.6 Ci/mmol and ethymemazine at 0.8 Ci/mmol. REFERENCES: 1. Buchman, 0. and Shimoni, M., in Phenothiazines and Structurally Related Drugs: Basic and Clinical Studies , edited by E. Usdin, H. Eckert and I. S. Forrest, Elsevier, Amsterdam, 1980, pp. 29-32. 2. Buchman, 0., Pri-Bar, I. and Shimoni, M., J. Label. Compounds Radiopharm., 14, 155 (1978) SELECTIVE LABELING OF CHLORPHENIRAMINE 0. Buchman, M. Shimoni, J. Azran, A. Cohen and Y. Hagag Chlorpheniramine is used as an antihistamine drug. Preliminary attempts to label this compound by isotopic hydrogen-tritium exchange .