Abstract Sulfenyl halides derived from the N-trifluoroacetamido methyl ester derivatives of cysteine, cysteinyiglycine and glutathione react stereoselectively with (5E)-and (5Z)- eicosenoic acids to provide, after separation of diastereomers and hydrolysis of the protecting groups, the fully saturated analogues of leukotrienes LTC 4, LTD 4, and LTE 4.