(3S)-1-((4a'R,6'S,7'S,8'R,8a'R)-7'-(benzyloxy)-8'-(methoxymethoxy)octahydro-3H,3'H-spiro[furan-2,2'-pyrano[3,2-b]pyran]-6'-yl)-3-((2S,3R,6S)-3-methyl-1,7-dioxaspiro[5.5]undecan-2-yl)butan-1-one