In the course of screening for new β-lactam antibiotics, a new carbapenem antibiotic named asparenomycin A and related antibiotics were found to be produced by Streptomyces tokunonensis sp. nov. (strain PA-31088) and Streptomyces argenteolus (strain PA-39504). The fermentation, isolation, and purification processes of asparenomycin A were described. Its physicochemical properties (colorless amorphous powder, solubility, positive EHRLICH's reaction, ninhydrin-negative, electrophoresis mobility, elemental composition) were determined. The molecular formula C₁₄H₁₆N₂O₆S for the free acid was confirmed by elemental analysis and FD mass spectrometry. Its structure, including R configuration at 5-C (derived from D-aspartic acid detection), E orientation at C-8, and R configuration of sulfoxide, was elucidated via chemical reactions (hydrolysis, oxidation), amino acid analysis, and X-ray crystallographic analysis of p-nitrobenzyl and methyl esters. Asparenomycin A is unique for its substituted ethylidene side chain, distinguishing it from known carbapenem antibiotics (e.g., thienamycin, olivanic acid derivatives). It shows broad antibacterial activity against Gram-positive (e.g., Staphylococcus aureus, Streptococcus pyogenes) and Gram-negative bacteria (e.g., Escherichia coli, Klebsiella pneumoniae) including β-lactamase-producing strains, and strong inhibitory activity against various β-lactamases (classes Ib, Ia, Ic, IIIa, IV, IVa).