2-((2R,6S)-6-(((4R,6S)-6-(((2R,3S,6R,8S,9S)-8-formyl-9-methoxy-3-methyl-1,7-dioxaspiro[5.5]undec-4-en-2-yl)methyl)-2,2-dimethyl-1,3-dioxan-4-yl)methyl)tetrahydro-2H-pyran-2-yl)ethyl pivalate

(S)-2-(but-3-en-2-yl)-1,3-dithiane