Synthesis and spectral properties of cholesterol- and FTY720-containing boron dipyrromethene dyes

Two analogues (1, 2) of free Cholesterol and one analogue (3) of the immunosuppressive sphingolipid FTY720 containing a boron dipyrromethene chromophore (BODIPY) were synthesized. The synthetic routes involved preparation of boron dipyrromethene moieties (5, 11), bearing a phenylethynyl group at different positions of the chromophore, and lipids (13, 20) bearing an azido group. The dye was tethered to the lipid via a 1,2,3-triazole in the linker by the click reaction. Analogues derived from 11 [in which an (E)-styrylethynyl moiety is bonded to C-5 of BODIPY] exhibited a marked red shift (approximately 70-80 nm) compared with those derived from 5 (in which a phenylethynyl moiety is bonded to C-8 of BODIPY).