The isolation and characterisation of (3R,5R)- and (3S,5R)-carbapenam-3-carboxylic acid from Serratia and Erwinia species and their putative biosynthetic role

Two new β-lactams (4b) and (5b), and (3S,5R)-carbapenam-3-carboxylic acid, have been isolated from strains of Serratia and Erwinia spp.; their possible role, and that of (5R)-carbapen-2-em-3-carboxylic acid as intermediates in the biosynthesis of the more complex members of the carbapenem family of β-lactam antibiotics is discussed.