WB-3559 A, B, C, and D are new fibrinolytic agents isolated from Flavobacterium sp. No. 3559. They were separated by liquid chromatography in a 1:4:1:4 ratio, with molecular formulas C₃₆H₆₆N₂O₇ (A), C₃₇H₆₈N₂O₇ (B), C₃₆H₆₈N₂O₇ (C), and C₃₇H₇₀N₂O₇ (D). Structural elucidation involved hydrogenation (converting A/B to C/D), methanolysis (yielding fatty acid methyl esters and acyl peptides), GC-MS (identifying fatty acids as 13-methyltetradecanoate and 13-methyl-4-tetradecenoate), FDMS/amino acid analysis (revealing glycine and L-serine), ¹H-NMR (identifying β-acyloxy acyl units), and EIMS (confirming fragment peaks matching structures). The total synthesis of WB-3559 D starting from D-glucose (via Wittig reaction, hydrogenation, acetonide cleavage, oxidation, and peptide coupling) confirmed its acyl part's absolute R-configuration. The structures of WB-3559 A, B, and C were clarified via EIMS of their methyl esters, and all components have R-configured acyl parts.