https://doi.org/10.1351/goldbook.D01661
Compounds having two @A00123@ substituted on ammonia or a primary amine acyl-NR-acyl. They are also known as secondary @A00266@ and, especially the cyclic examples derived from diacids, as @I02948@, e.g. [RC(=O)]2NR, RS(=O)2NHC(=O)R.