The Synthetic Routes of Entecavir intermediate N5

Entecavir is an antiviral drug commonly used to treat hepatitis B virus infection.
It belongs to a class of drugs known as nucleotide analogues, which work by inhibiting the viral DNA polymerase activity.
Entecavir is a complex molecule with a structural formula of (2R)-2-(2-((2S)-2-((S)-2-(2-(2-hydroxyethoxy)ethylamino)-N-(2-(2-((2S)-5,6,7,8-tetrahydro-2H-pyrano[2,3-d]pyrimidin-4-yl)amino)-4-oxo-1,2,3,4-tetrahydroquinazoline-6-carbonyl)amino)-8-(2-(2-((2S)-5,6,7,8-tetrahydro-2H-pyrano[2,3-d]pyrimidin-4-yl)amino)-4-oxo-1,2,3,4-tetrahydroquinazoline-6-carbonyl)amino)-N6-(2-(2-((2S)-2-((S)-2-(2-(2-hydroxyethoxy)ethylamino)-N-(2-(2-((2S)-5,6,7,8-tetrahydro-2H-pyrano[2,3-d]pyrimidin-4-yl)amino)-4-oxo-1,2,3,4-tetrahydroquinazoline-6-carbonyl)amino)-8-(2-(2-((2S)-5,6,7,8-tetrahydro-2H-pyrano[2,3-d]pyrimidin-4-yl)amino)-4-oxo-1,2,3,4-tetrahydroquinazoline-6-carbonyl)amino)-N6-(2-(2-((2S)-2-((S)-2-(2-(2-hydroxyethoxy)ethylamino)-N-(2-(2-((2S)-5,6,7,8-tetrahydro-2H-pyrano[2,3-d]pyrimidin-4-yl)amino)-4-oxo-1,2,3,4-tetrahydroquinazoline-6-carbonyl)amino)-8-(2-(2-((2S)-5,6,7,8-tetrahydro-2H-pyrano[2,3-d]pyrimidin-4-yl)amino)-4-oxo-1,2,3,4-tetrahydroquinazoline-6-carbonyl)amino)-N6-(2-(2-((2S)-2-((S)-2-(2-(2-hydroxyethoxy)ethylamino)-N-(2-(2-((2S)-5,6,7,8-tetrahydro-2H-pyrano[2,3-d]pyrimidin-4-yl)amino)-4-oxo-1,2,3,4-tetrahydroquinazoline-6-carbonyl)amino)-8-(2-(2-((2S)-5,6,7,8-tetrahydro-2H-pyrano[2,3-d]pyrimidin-4-yl)amino)-4-oxo-1,2,3,4-tetrahydroquinazoline-6-carbonyl)amino)-N6-(2-(2-((2S)-2-((S)-2-(2-(2-hydro