Structure–activity relationship (SAR) of sphingosine-1-phosphate receptor agonists with a dihydronaphthalene scaffold was investigated. Compound 1 was modified to improve S1P1 agonistic activity and in vivo peripheral lymphocyte lowering (PLL) activity without impairing selectivity over S1P3 agonistic activity. A detailed SAR study of the terminal lipophilic part revealed that the introduction of substituents on the propylene linker and the terminal ...