The analyses of Murcko scaffolds. (A) Shows the similarity heatmap between the original fentanyl and its analogues’ Murcko scaffolds and the Murcko scaffolds of generated molecules. Each row represents the scaffold extracted from the original fentanyl and its analogue data, and each column represents the scaffold extracted from 546 validly generated molecule data. The color indicates the degree of similarity. The darker the color, the higher the similarity. The lighter the color, the less similar it is. (B) Shows some Murcko scaffolds we selected.