The new proposed NCBs were among the most stable tested, with three structures surpassing stability of those currently in our library: R3sub-II (-117.1 kcal/mol, -490.1 kJ/mol), R2sub-IV (-120.0 kcal/mol, -502.3 kJ/mol), and R1sub-IV (-117.3 kcal/mol, -490.9 kJ/mol) (Figure ). The increased stability of these NCBs relative to the remainder of the library is promising since it shows that we can use trends in existing data to suggest and successfully design new NCBs with enhanced stability. Furthermore, the higher stability seen with the new substituents at each position supports our hypotheses that NCBs with aryl R1 substituents, electron-withdrawing R2 substituents, and bulky and/or electron-withdrawing R3 substituents are likely to be stable structures. With this new information about how substituent identity and properties at each position impact stability, we can make informed decisions to eventually suggest novel NCBs which will be more resistant to decomposition via C5-C6 saturation.