4-Vinyl Syringol (4VS) is a member of a group of aromatic phenols that includes vanillin and 4-vinyl guaiacol but possesses minimal sensory properties compared with the latter compound.

4VS is derived via decarboxylation—the removal of a carbon dioxide molecule—from the precursor sinapic acid (a hydroxycinnamic acid) and is found in beer. It is produced in a similar manner to 4-vinyl guaiacol. See 4-vinyl guaiacol. Although no current information exists to show the occurrence of this compound in malt or hops (the usual source of beer phenols), 4VS imparts a smoked or burned note to beer at a threshold of about 0.5 parts per million. It is a compound identified in fresh beers and aged lager beers and may be associated with aged beer flavor. Tasting panelists describe its flavor as “smoky-old beer” or tobacco-like. The smoke used for the production of rauchbier malt has also been suggested as a source of 4VS. Some research has intriguingly suggested that the “wild” yeast brettanomyces might also be capable of producing this flavor, which is usually considered undesirable. If this is so, then the flavor may be apparent in some lambic beers and other beers fermented by brettanomyces yeasts. 4VS is also found in some Bavarian-style weissbiers, where it appears to contribute a smoky background note.

See also brettanomyces, lambic, and weissbier.