Cephalosporin derivatives nuclear analogues

Another distant nuclear analogue of cephalosporins is compound (50), a 2-oxaoctam derivative, 2-oxa-7a-phenyl-octam, formed by photolysis of the corresponding diazoamide [32]. 

A carbon analogue of penicillin V (Ic) was resistant to Bacillus cer-eus B l ctamase and moderately active against gram-positive organisms.6 ) Several 2-acetoxymethyl penicillins (2ja,y6 and 2-spirocyclopropyl cephalosporins (3 )65 vere prepared. Various chemical procedures were developed for the 7(6)a-methoxylation of B-lactam antibiotics.66-72 Conversion of penicillins to cephalosporins was achieved by new synthetic routes.73-76 Some [2,3]-fused tricyclic cephem derivatives (4a-c) were synthesized.77,78 Compound displayed significant antibiotic activity.78 Racemic cephalothin, 7-methoxycephalothin, and cefoxitin were obtained by total synthesis of a novel type.79-81 nuclear analogue of a 7-methylcephalosporin (5), prepared by total synthesis, lacked antibiotic activity,82... 

R = Ph, R = Et), Finally, there have been a number of interesting reports on the synthesis of nuclear analogues of penicillins and cephalosporins by the irradiation of a-diazo-amide derivatives. Thus irradiation of the diazocompound (81) in carbon tetrachloride gave the oxapenam (82) in 55% yield, presumably by a carbene insertion reaction. ... 

Several review articles have appeared during the past two years. " The rearrangements of penicillanic acid derivatives have been the subject of one review, while the total synthesis of nuclear analogues of penicillin and cephalosporins and recent developments in the chemistry of the j3-lactam antibiotics have also been reviewed. " ... 

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