Zopiclone
Zopiclone was developed and first introduced in 1986 by Rhône-Poulenc S.A., now part of Sanofi-Aventis, the main worldwide manufacturer. Initially, it was promoted as an improvement on benzodiazepines, but a recent meta-analysis found it was no better than benzodiazepines in any of the aspects assessed. On April 4, 2005, the U.S. Drug Enforcement Administration listed zopiclone under schedule IV, due to evidence that the drug has addictive properties similar to benzodiazepines.
Dimethylaminopivalophenone
Dimethylaminopivalophenone is an opioid analgesic. with a potency ½ that of morphine. It was initially discovered by Russian scientists in 1954 and subsequently rediscovered in the US in 1969. Its LD in mice is 83 mg/kg. It has never been marketed commercially, likely due to its low potency and lack of benefits compared to existing agents.