2-Oxabicyclo[2.2.1]heptane-1-carboxylic acid, 4,7,7-trimethyl-3-oxo-, (9R,10R)-9,10-dihydro-4,8,8-trimethyl-2-oxo-10-[[(4,7,7-trimethyl-3-oxo-2-oxabicyclo[2.2.1]hept-1-yl)carbonyl]oxy]-2H,8H-thiopyrano[2,3-f][1]benzopyran-9-yl ester AIDS-210627 AIDS210627