https://doi.org/10.1351/goldbook.D01661
Compounds having two @[email protected] substituted on ammonia or a primary amine acyl-NR-acyl. They are also known as secondary @[email protected] and, especially the cyclic examples derived from diacids, as @[email protected], e.g. [RC(=O)]2NR, RS(=O)2NHC(=O)R.