Enantiomeric 3-hydroxypent-4-enethionamides from thioglucosides of Crambe and Brassica seeds by action of ferrous salts

epi-Progoitrin, the major thioglucoside of Crambe abyssinica seed, is cleaved by ferrous salts to yield (S)-1-cyano-2-hydroxy-3-butene and (S)-3-hydroxypent-4-enethionamide. The products are the same whether obtained from the purified thioglucoside or from the seed meal. Identical behavior was observed for seed meal of Brassica napus, which gave corresponding derivatives of the opposite configuration. Optical rotatory dispersion and proton magnetic resonance studies suggest the existence of solvent-dependent differences in rotamer composition for the 3-hydroxypent-4-enethionamides.