Desulpho-3-butenylglucosinolate is considered to be a potential late stage precursor in the biosynthesis of (R)-2-hydroxy-3-butenylglucosinolate (progoitrin) and 3-butenylglucosinolate (gluconapin) in Brussica. Chemically synthesized 4,5-3H-4-pentenethiohydroxamic acid when administered to developing seedlings of Brassica napus cv Bienvenu was found to be well incorporated into both 2-hydroxy-3-butenylglucosinolate and 3-butenylglucosinolate, while feeding experiments with [14C]methionine have shown that de nova biosynthesis is slow. Analysis of seeds and developing seedlings has shown that levels of 2-hydroxy-3-butenylglucosinolate are maintained while 3-butenylglucosinolate levels are considerably reduced.