This is a chiral building block and key intermediate in the synthesis of Darunavir (DRV), a potent HIV-1 protease inhibitor used in antiretroviral therapy. The compound is the 4-nitrophenyl carbonate ester of (3R,3aS,6aR)-hexahydrofuro[2,3-b]furan-3-ol, featuring the characteristic bis-tetrahydrofuran (bis-THF) moiety. This activated form facilitates nucleophilic attack by amines, enabling the formation of carbamate linkages to install the bis-THF group at the P2 position of the protease inhibitor scaffold. Its stereochemical purity is crucial for the biological activity of the final drug. This specialty chemical reagent is essential in pharmaceutical manufacturing processes for producing high-purity APIs.