Synthesis of delta 3-1-methylene-1-carbacephems

The total synthesis of (+/-)-1-methylene-2,2- dimethyl-7-amino-1-carbacephem-4-carboxylic acid (1) is described. The reaction scheme was essentially that described by Christensen et al. for the synthesis of (+/-)-1-carbacephems. In vitro antibacterial activities of the 7-phenoxyacetyl and 7-D-alpha-phenylglycyl derivatives of 1 were compared with those of 7-(phenoxyacetamido)desacetoxycephalosporanic acid and cefalexin. Derivatives of 1 were 2-4 times less active against most of the sensitive organisms than the corresponding 7-aminodesacetoxycephalosporanic acid analogues. The activity of the 7-D-alpha-phenylglycyl derivative of 1 however was about 20 times lower than that of cefalexin when measured against Staphylococcus aureus ATCC 6538P.