3-(4-(((4-(Butoxycarbonyl)-7-oxabicyclo[4.1.0]hept-3-yl)carbonyl)oxy)butyl) 4-butyl 7-oxabicyclo[4.1.0]heptane-3,4-dicarboxylate 6624-41-5 AIDS-124813 AIDS124813 NSC53364