<unk>  (IUPAC systematic name: butanedioic acid; historically known as spirit of amber) is a dicarboxylic acid which plays a biochemical role in the citric acid cycle.
Succinic acid
Meglutol
Choline
Malic acid
Acetaldehyde
Uridine triacetate
Triethanolamine
Glutaconyl-CoA