Natural cannabinoids produced by the plant cannabis sativa.
The first generation of retail synthetic cannabinoids including the famed original, JWH-018.
Some new synthetic cannabinoids brought to prominence by the DEA emergency scheduling of JWH-018, JWH-073, JWH-200, and CP-47,497.
Substitution of some simple alkyl chains at the 4-position of the napthyl ring of JWH-018 can produce some highly potent (and more importantly) legal analogs.
One of the major concerns raised about the first generation synthetic cannabinoids was their napthalene ring and possible carcinogenic metabolites. The next generation phenylacetylindoles do not have a napthalene ring, and do not share this risk.
As synthetic cannabinoids moved from the underground to the mainstream, obscurity ceased to be a defense from drug enforcement authorities. Legal pressures have now created a situation where the inelastic demand of recreational drug users causes overseas manufacturers to seek the highest potency compounds in order to minimize risk of seizure.