Isosafrole is a phenylpropene

Phenylpropene

Phenylpropenes, propenylphenols or allylbenzenes are a class of phenylpropanoids, a type of polyphenols.The phenylpropenes, including eugenol, chavicol, safrole and estragole, are derived from the monolignols. These compounds are the primary constituents of various essential oils....

, a type of aromatic organic chemical with a smell similar to anise

Anise

Anise , Pimpinella anisum, also called aniseed, is a flowering plant in the family Apiaceae native to the eastern Mediterranean region and Southwest Asia. Its flavor resembles that of liquorice, fennel, and tarragon.- Biology :...

 or licorice. It is found in small amounts in various essential oils, but is most commonly obtained by isomerizing the plant oil safrole

Safrole

Safrole, also known as shikimol, is a phenylpropene. It is a colorless or slightly yellow oily liquid. It is typically extracted from the root-bark or the fruit of sassafras plants in the form of sassafras oil , or synthesized from other related methylenedioxy...

.

It forms two geometric isomers: cis-isosafrole and trans-isosafrole.

Isosafrole is a precursor for MDP2P

MDP2P

3,4-phenyl-2-propanone , is a chemical compound consisting of a phenylacetone moiety substituted with a methylenedioxy functional group, an entactogen and stimulant of the phenethylamine, amphetamine, and cathinone classes...

 which is converted into the psychoactive drug

Psychoactive drug

A psychoactive drug, psychopharmaceutical, or psychotropic is a chemical substance that crosses the blood–brain barrier and acts primarily upon the central nervous system where it affects brain function, resulting in changes in perception, mood, consciousness, cognition, and behavior...

 MDMA ('ecstasy'). As such requires permits to purchase or sell in any significant quantity in the US.