A GENERAL SYNTHETIC ROUTE FOR PREPARING ETHER PHOSPHOLIPIDS SUITABLE FOR IMMOBILIZATION - A PHOSPHOTRIESTER APPROACH

A synthetic route was developed to prepare ether phospholipid (PL) lig ands suitable for immobilization. PL ligand design included an omega-c arboxyl functional group to assure proper molecular orientation during immobilization; i.e., the polar lipid head group protrudes from the s urface. However, during immobilization, PL ligands required protecting groups to eliminate the possibility of the PL binding upside down. Fo ur synthetic PL ligands were prepared that contain both omega-carboxyl groups for immobilization and protecting groups in the polar head gro up; these carboxyl-PL ligands are analogs of phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylglycerol (PG), and phosphat idic acid (PA). The critical synthetic step during PL synthesis is the phosphorylation step which usually has the lowest yield of all other steps. This is the first report demonstrating that o-chlorophenyl dich loro phosphate (CPDCP) can be used as a mild phosphorylation reagent f or the preparation of PL analogs. Phosphorylation with CPDCP is routin ely 50-90 % efficient depending on the analog, but more important is t hat the protecting groups associated with PE, PS, PG, and PA are stabl e during this critical synthetic step. After immobilization of the car boxyl-PL ligands, acidic or basic solution conditions are needed for d eprotection and generation of free PE, PG, PS, and PA polar lipid head groups which protrude from the surface. This work demonstrates that CP DCP is an excellent synthetic reagent for all ether PL analogs either with or without omega-carboxyl functional groups.