Cycloadditions of Cephalosporins. A Comprehensive Study of the Reaction of Cephalosporin Triflates with Olefins, Acetylenes, and Dienes To Form [2 + 2] and [4 + 2] Adducts
作者:Richard L. Elliott、Neville H. Nicholson、Fiona E. Peaker、Andrew K. Takle、Christine M. Richardson、John W. Tyler、Janet White、Michael J. Pearson、Drake S. Eggleston、R. Curtis Haltiwanger
DOI:10.1021/jo970176s
日期:1997.7.1
Novel polycyclic cephalosporins are formed by the reaction of cephalosporin triflates with various unsaturated compounds in the presence of Hunigs base. 2,3-Fused cyclobutane and cyclobutene cephems are obtained with olefins and acetylenes, respectively, whereas [4 + 2] cycloadducts are obtained with furan. The reaction has been rationalized by invoking the intermediacy of a strained 6-membered cyclic allene. The allene undergoes an orbital symmetry allowed concerted (pi)2(8), + (pi)2(a), cycloaddition with olefins and acetylenes and a (pi)4(s) + (pi)2(s) cycloaddition with furan. The regiochemistry of the [2 + 2] cycloadducts is independent of the substitution of the unsaturated component and of the oxidation state of the cephalosporin sulfur atom. However in the case of the [4 + 2] adducts, the sulfur oxidation state determines the regiochemistry of the addition. Carbacephalosporins also participate in this reaction with olefins but require a stronger base such as DBU. Thus the reaction described provides a facile, one-step procedure for the production of a rich variety of novel polycyclic cephalosporins.
Cycloadditions of cephalosporins. A general synthesis of novel 2,3-fused cyclobutane and cyclobutene cephems
作者:Richard L. Elliott、Andrew K. Takle、John W. Tyler、Janet White
DOI:10.1021/jo00077a007
日期:1993.12
The cephalosporin triflate (1) reacts with a wide variety of olefins and acetylenes in the presence of a base to give 2,3-fused cyclobutane and cyclobutene derivatives, respectively.
Cephalosporin derivatives
申请人:Pfizer Inc.
公开号:US05578592A1
公开(公告)日:1996-11-26
Compounds of formula (I) or salts thereof: wherein R.sup.1 is hydrogen, methoxy or formamido; R.sup.2 is an acyl group; CO.sub.2 R.sup.3 is a carboxy group or a carboxylate anion, or R.sup.3 is a readily removable carboxy protecting group or a pharmaceutically acceptable salt-forming group or in vivo hydrolysable ester group; R.sup.4, R.sup.5, R.sup.6 and R.sup.7 independently represent hydrogen or a bond or a substituent group or may form a cyclic system. These compounds have antibacterial activity.