1-[2,3-Dimethyl-2-(2-methylbut-3-en-2-yl)-3-furyl]-3,5-dihydroxy-4-methoxy-hexan-2-one

A 121 is a non-polyene antifungal antibiotic, produced by an unidentified strain of Streptomyces. It is active against a number of filamentous fungi including some plant and human pathogens. The presence of an alpha-ketol system in the molecule is required for A 121 to exhibit antibiotic properties.