This compound, with the CAS number 114748-67-3, is a complex heterocyclic molecule. Its systematic name is 2-Amino-3,7-dihydro-5-iodo-7-[(2R,5S)-tetrahydro-5-(hydroxymethyl)-2-furanyl]-4H-pyrrolo[2,3-d]pyrimidin-4-one. The structure features a pyrrolo[2,3-d]pyrimidine core, which is a bicyclic heterocyclic system, substituted with an amino group, an iodine atom, and a tetrahydrofuran ring bearing a hydroxymethyl group. This molecule is a key synthetic intermediate in the production of nucleoside analogues. Specifically, it is a crucial precursor in the synthesis of the antiviral drug **Entecavir**, which is a potent and selective inhibitor of hepatitis B virus (HBV) replication. The iodine atom and the specific stereochemistry of the tetrahydrofuran moiety are essential for the subsequent steps that construct the final carbocyclic nucleoside structure of Entecavir. As a specialized building block for a specific active pharmaceutical ingredient (API), its primary and almost exclusive application is within pharmaceutical research and manufacturing processes. Its synthesis and handling require expertise in nucleoside chemistry and asymmetric synthesis due to its chiral centers and functional group complexity.