RK-682 is a dimeric calcium complex of the major analogue of a tetronic acid complex isolated from Streptomyces. Although reported by researchers at RIKEN in 1995, subsequent synthesis in 2001 showed that RK-682 was in fact the calcium complex formed during silica chromatography. Confusion about the structure of RK-682 has lead to the monomeric sub-unit, TAN 1364B (3-hexadecanoyl-5-hydroxymethyltetronic acid) being mis-named as RK-682 by many suppliers. As either the dimer or monomer, RK-682 inhibits protein tyrosine phosphatases, phospoholipase A2, heparinase and HIV-1 protease. However, is unclear whether biological activity is due to the monomer (TAN 1364B) or dimeric complex (RK-682).