Penem benzyl esters substituted at the 6-position with small alkyl gro
ups and at the 3-position with a variety of carbon and heteroatom grou
ps were prepared as inhibitors of human leukocyte elastase (HLE). The
structure activity relations found for the these positions are discuss
ed in relation to known cephalosporin inhibitors and some important st
ereochemical implications are reported for inhibition of HLE by these
beta-lactam structures.