{8-[(2,6-dideoxy-3-C-methylhexopyranosyl)oxy]-10,12-dihydroxy-7,13a-dimethoxy-5-methyl-11-oxo-3a,8,9,10,11,13a-hexahydro-4H-spiro[2,4-epoxyfuro[3,2-b]naphtho[2,3-h]chromene-1,2'-oxiran]-2-yl}(methoxy)methyl 2,6-dideoxy-4-O-(2,6-dideoxy-3-C-methylhexopyran