The substituted N-acyl homoserine lactones have the formula (I) wherein R is a saturated or unsaturated straight chain or branched chain aliphatic hydrocarbyl group containing from 5 to 14 carbon atoms; R2 is H or a 1-4C alkyl group; R3 is H or F; and any enantiomer thereof. These compounds exhibit immunosuppressant activity while exhibiting reduced biosensor (autoinducer) activity compared to known N-acyl homoserine lactones.