Semisynthesis and purification of homogeneous plasmenylcholine molecular species

Methods for the efficient use of limiting amounts of fatty acid probes in the synthesis of individual molecular species of plasmenylcholine have been developed. Plasmenylcholine molecular species were synthesized through acylation of homogeneous 1-O-(Z)-hexadec-1′-enyl-sn-glycero-3-phosphocholine utilizing fatty acid anhydrides generated in situ from combined pools of reactant and recycled fatty acids by repeated addition of small amounts (10 mol%) of N,N′-dicyclohexylcarbodiimide. The efficient generation of reactive anhydrides was accomplished through minimizing irreversible formation of N-acyl urea adducts by maintaining a persistent molar excess of fatty acid (with respect to carbodiimide) during the entire reaction time course. The synthesis of multiple different sn-2 labeled plasmenylcholine probes for utilization in fluorescence, ESR, or ²H NMR spectroscopy as well as isotopically labeled plasmenylcholines for metabolic studies has been achieved in good yield (40-50% of theoretical yield based on fatty acid) by these methods. Rapid and effective purification methods utilizing high-performance liquid chromatography were developed for both large- and small-scale purifications of individual reaction mixtures which collectively resulted in the isolation of homogeneous plasmenylcholine molecular species in high yield from limiting amounts of fatty acid probes.