The second structural image left off the phosphate. The upper ring is cytosine, and the 4 carbon ring at the bottom is ribose. To see this in detail, including reaction steps and kinetics see;
“Prebiotic synthesis of simple sugars by photoredox systems chemistry” (Ritson, D. and Sutherland, J.D., 2012 Nature chemistry, 4(11), p.895).
2 Likes