中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
西咪替丁 | cimetidine | 51481-61-9 | C10H16N6S | 252.343 |
Etintidine (4), a new histamine H2-receptor antagonist, was compared with cimetidine (1) for susceptibility to in vitro nitrosation at pH 1 and pH 3. Each agent formed two mono-N-nitrosoguanidine derivatives: N-cyano-N′-2-[(5-methyl-1H-imidazol-4-yl)methylthio]ethyl}-N″-nitroso-N″-(2-propynyl)guanidine (5) and N-cyano-N′-2-[5-methyl-1H-imidazol-4-yl)methylthio]ethyl}- N′-nitroso-N″-(2-propynyl)guanidine (6) from etintidine and N-cyano-N′-methyl-N″-2-[(5-methyl-1H-imidazol-4-yl)methylthio]ethyl}- N′-nitrosoguanidinc (2) and N-cyano-N′-methyl-N"-2-[(5-methyl-1H-imidazol-4-yl)methyl-thio]ethyl}-N′-nitrosoguanidine (11) from cimetidine. The N-nitroso derivative 5 from etintidine cyclized to 2-cyanoimino-3-2-((5-methyl-1H-imidazol-4-yl)methylthio]ethyl}-N″-methylene-1-nitroso-imidazoline (7) at neutral or basic pH's. Both agents were nitrosated less at pH 3 than at pH 1, and at both pH's nitrosation of etintidine was considerably less than that of cimetidine. At pH 1, with a nitrite concentration about 150–500 times that expected in fasting human gastric juice, formation of 5 and 6 from etintidine was barely detectable (each < 0.5%). Comments are made on the standard WHO conditions for investigating nitrosation of drugs.