H₂C----NH | | (V) H₂C C:NH \ / Se The literature for the other normal carbamides is listed in the bibliography(27). Selenoantipyrines, selenosaccharine, selenoindigoes have also been prepared. Thiophene and its derivatives are of considerable therapeutic interest. Thiophene itself is found to be useful in lessening the elimination of sulphuric acid in urine, and is employed in the dermatological practice. Sodium thiophene sulphonate, thiophenetetra-bromide, thiophene diiodide, are all medicinals(23). A number of selenophenes are recorded in the literature. Their relation to the selenazoles may be easily seen from the following formulas: CH--CH CH--N || || || || CH CH CH CH \ / \ / Se Se Selenophene Selenazole Dimethyl selenophene was prepared from acetonyl acetone and phosphorous pentaselenide, CH₃ CH₃ / / HC=C HC=C | \ | \ | OH + P₂Se₅ = | Se | OH | / | / HC=C HC=C \ \ CH₃ CH₃ The compound thus obtained is stated to have the same odor as thiophene, but no mention is made in regard to its uses(28). Selenophene was prepared from sodium succinate and phosphorous triselenide, or by conducting ethylselenide through hot tubes(29). Some selenazoles find application also in medicine. At present only the isoazoles are known to have physiological uses. One of them was prepared from anthraquinone selenocyanide, by the action of ammonia under pressure(30). NH₂H N-Se O || C SeCN C /\ / \ /\ /\ / \ /\ | | | | = | | | | + HCN + H₂O \/ \ / \/ \/ \ / \/ C C O O Another type of azoles, benzoselendiazole (piaselenol) and five of its derivatives, have been also described as medicinals(31). The diazole itself has the following structure, N N //\ /|\ //\ / \ | | | Se or | || Se \\/ \|/ \\/ \ / N N Diazoles of the following structure are also known, but no data were found, regarding their physiological action(32): N-N N-N / \ // \\ CH₃C CCH₃ C₆H₅C CC₆H₅ \ / \ / Se Se Dimethyl-seleno-diazole Diphenyl-seleno-diazole