Propenyl
From Infogalactic: the planetary knowledge core
In organic chemistry, propenyl is the species with the formula CH=CHCH3. Many propenyl compounds are known, such as cis- and trans-1-chloropropene, propenylbenzene (β-methylstyrene). Propenyl compounds are isomeric with and less common than allyl compounds.

The three common precursors to lignin are derivatives of propenylbenzene: paracoumaryl alcohol (1), coniferyl alcohol (2) and sinapyl alcohol (3).
See also
References
http://www.biology-online.org/dictionary/Propenyl
http://www.thefreedictionary.com/Propenyl
Chemicals With Propenyl Radicals
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