Use of Bistrimethylsilylated Intermediates in the Preparation of Semisynthetic 7-Amino-3-substituted-cephems. Expedient Syntheses of a New 3-cephalosporin

Article abstract of DOI:10.1021/jo00240a009

Several "one-pot" methods for conversion of 7-ACA (6) to a variety of 7-amino-3-(ammoniomethyl)- or 7-amino-3-<<(heteroaryl)thio>methyl>cephalosporin derivatives via bistrimethylsilylated intermediates are presented.For example, bistrimethylsilylation of 7-ACA (6) in 1,1,2-trichlorotrifluoroethane (Freon TF) using HMDS and 3 mol percent TMSI, followed by treatment with 1.15 equiv of TMSI and subsequent reactions with tertiary alicyclic or heteroaromatic amines or heteroaromatic thiols, led to the desired products in good yields.Alternatively, novel reaction of the bistrimethylsilylated derivative 15 with amine/TMSI adducts in Freon TF at 35 deg C provided an alternative approach to some 7-amino-3-(ammoniomethyl)cephalosporins.The solvent dependence of Δ³/Δ² isomer ratios in quaternization reactions of 11 with N-methylpyrrolidine is presented.Hypotheses for the explanation of experimental results observed on reaction of 15 in Freon TF with amine/TMSI adducts are presented.Acylation of 17 (X = Cl, I) with 8 in aqueous THF provided 18 (BMY-28142) as its sulfate salt in overall yields of 18percent and 43percent, respectively, from 7-ACA (6).