Both onions (Allium cepa) and garlic (A. sativum) contain a variety of novel sulfur compounds, some of which possess significant pharmacological activity.'The unusual amino acid tram-(+)-S-1-propenyl-L-cysteine sulfoxide (1) has been isolated from onions, z and it has been shownZ to be the precursor of the lachrymatory principle characteristic of this plant,(Z)-propanethial S-oxide (2)(eq l).'Investigations by Granroth4
