1-(6-Amino-9H-purin-9-yl)-1-deoxy-beta-D-ribofuranuronic acid ethyl ester 35803-57-7 50663-70-2 A-40557 Abbott 40557 Ethyl adenosine-5'-carboxylate beta-D-Ribofuranuronic acid, 1-(6-amino-9H-purin-9-yl)-1-deoxy-, ethyl ester