4(2H)​-​Benzofuranone, 3,​5-​dihydro-​6-​hydroxy-​2-​(1-​hydroxy-​1-​methylethyl)​-​5,​5-​bis(3-​methyl-​2-​buten-​1-​yl)​-​7-​(2-​methyl-​1-​oxopropyl)​-​, stereoisomer