(4S)-3,4-dihydroavermectin B1a aglycone

(3E<2E,4S,5S,6E,8<2R,4S,6S,8R(S),9S>>,3aS,4S,6S,7R,7aR)-octahydro-3a,7-dihydroxy-3-<5-hydroxy-8-<4-hydroxy-9-methylpropyl)-1,7-dioxaspiro<5.5>undec-10-en-2-yl>-4,6-dimethylocta-2,6-dienylidene>-6-methylbenzofuran-4-carboxylic acid