(S)-2-((2-((((9-((2-hydroxyethoxy)methyl)-6-oxo-6,9-dihydro-1H-purin-2-yl)amino)methyl)amino)-6-oxo-1H-purin-9(6H)-yl)methoxy)ethyl 2-amino-3-methylbutanoate
(S)-2-((2-((((9-((2-hydroxyethoxy)methyl)-6-oxo-6,9-dihydro-1H-purin-2-yl)amino)methyl)amino)-6-oxo-1H-purin-9(6H)-yl)methoxy)ethyl 2-amino-3-methylbutanoate