Determination of the absolute configuration of the glucosinolate methyl sulfoxide group reveals a stereospecific biosynthesis of the side chain

Oxidation of the sulfide function in the side chain of 4-methylthiobutylglucosinolate, which is catalyzed by a flavin monooxygenase in Arabidopsis thaliana, proceeds stereospecifically to produce (RS)-4-methylsulfinylbutylglucosinolate exclusively.