3′-[4-[[4-[[(3R,5aS,6R,8aS,9R,10S,12R,12aR)-Decahydro-3,6,9-trimethyl-3,12-epoxy-12H-pyrano[4,3-j]-1,2-benzodioxepin-10-yl]oxy]-2-methyl-1,4-dioxobutoxy]methyl]-1H-1,2,3-triazol-1-yl]-3′-deoxythymidine