Potential Antiradiation Agents. II. Selenium Analogs of 2-Aminoethylisothiouronium Hydrobromide and Related Compounds^1-3

In view of the effectiveness of aminoethyl mercaptan (cysteamine) and of 2-aminoethylisothiouronium (AET) salts in protecting animals against ionizing radiation, efforts were made to prepare even more active analogs of the compounds. Sulfur is considered to be essential to the radioprotective action of cysteamine analogs; however, the selenium analog of cysteamine can shield mice against radiation. Since the atomic radii of sulfur and of selenium are similar, sulfur and selenium analogs may be assumed to have the same ability of fit receptor sites. The selenium analog of AET was prepared by the reaction of selenourea with 2-bromoethylamine hydrobromide. Treatment of the selenouronium salt with NaOH yielded 2-selenoethylguanidine, which was isolated as the flavianate salt. The reaction of 2-aminoethylisoselenouronium hydrobromide with boiling water resulted in the formation of 2-aminoselenazoline. Through the reaction of 2- methylaminoethyl. 2dimethylaminoethyl, and 2-diethylaminoethyl halides with selenourea the corresponding 2-alkylaminoethyl selenouronium salts were obtained. Similarly, 3-aminopropylisoselenouronium hydrobromide was synthesized.