Syntheses of and chemotactic responses elicited by fMet-Leu-Phe analogs containing difluoro- and trifluoromethionine

N-Formylmethionylleucylphenylalanine tripeptides containing either L-difluoro- or L-trifluoromethionine as replacements for methionine were synthesized by solution methods. The fluorinated peptides were found to have potent chemoattractant activities on human neutrophils. Ab initio calculations were utilized to further understand the changes in electronic properties of the methionine side chain upon fluorination.