4-amino-1-[(1R,2R,4R,5R)-2-(hydroxymethyl)-7-oxido-7-oxo-3,6,8-trioxa-7$l^{5}-phosphabicyclo[3.3.0]octan-4-yl]pyrimidin-2-one
4-amino-1-[(1R,2R,4R,5R)-2-(hydroxymethyl)-7-oxido-7-oxo-3,6,8-trioxa-7$l^{5}-phosphabicyclo[3.3.0]octan-4-yl]-2-pyrimidinone
4-amino-1-[(1R,2R,4R,5R)-7-keto-2-methylol-7-oxido-3,6,8-trioxa-7$l^{5}-phosphabicyclo[3.3.0]octan-4-yl]pyrimidin-2-one