209216-23-9 6H-Purin-6-one, 2-amino-1,9-dihydro-9-((1S,3R,4S)-4-hydroxy-3-(hydroxymethyl)-2-methylenecyclopentyl)-, monohydrate BMS 200475-01 Baraclude Entecavir Entecavir [USAN:INN] SQ 34676