| 摘要 |
<p>1,239,814. 7 - Aminocephalosporanic acid derivatives. KONINKLIJKE NEDERLANDSCHE GIST - EN SPIRITUS - FABRIEK N.V. 26 July, 1968 [7 Aug., 1967], No.35757/68. Heading C2C. A 7-aminocephalosporanic acid derivative of Formula I wherein R is H or an esterified OH group, is prepared by treating a 4-silyl ester of Formula II wherein R is as above, R a is an acyl group having any functional groups present blocked, and R b is a silyl group, with an agent (A) to form a 7-imino halide preferably at a temperature below -15‹ C., treating the 7-imino halide with an agent (B) to form a 7-imino ether, preferably at a temperature below-15‹ C., and hydrolysing or alcoholysing the product obtained to split the imino ether and form the compound of Formula I. Agent (A) may be phosphorus pentachloride or phosphorus oxychloride and agent (B) is an alcohol e.g. methanol or ethanol. The reaction takes place in the presence of a tertiary amine. The 4-silyl ester of Formula II is prepared by reacting the corresponding free acid or salt thereof with a silylating agent of formula R 1 R 2 R 3 SiX, wherein X is halogen and R 1 , R 2 and R 3 , which may be the same or different, are hydrocarbon radicals or halogen atoms or one of R 1 , R 2 or R 3 may be a hydrogen atom; or where X is amino or HNSiR 1 R 2 R 3 and R 1 , R 2 and R 3 may be the same or different and are hydrocarbon radicals. Cephalosporins of Formula III wherein R c is an acyl group other than the R a group present in the starting material, are produced by acylating in a conventional manner the compounds of Formula I. Pharmaceutical compositions comprise a cephalosporin of Formula III when prepared by the process of the invention, and a pharmaceutical carrier.</p> |
