Rapeseed meal autolysis. Formation of diastereomeric (2R)-1-cyano-2-hydroxy-3,4-epithiobutanes from progoitrin

When defatted seed from Brassica napus L. var. Regina II (a rapeseed) was autolyzed, its major thioglucoside (progoitrin) underwent degradation analogous to that for epiprogoitrin in Crambe abyssinica seed meal. Depending on the conditions, (R)-1-cyano-2-hydroxy-3-butene and the diastereomeric forms of (2R)-1-cyano-2-hydroxy-3,4-epithiobutane were formed in autolyzed B. napus meal instead of (S)-goitrin. The configuration at the chiral center containing the hydroxyl is assigned on the basis of known data. The configuration at carbon 3 of the episulfides is predicted on the basis of the optical rotatory dispersion data.