Chemical synthesis of sn-3-phosphatidyl sulfocholine, a sulfonium analog of lecithin

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Abstract
A sulfonium analog of lecithin was reported to replace the ubiquitous phosphatidyl choline in a non-photosynthetic diatom, Nitzschia alba. The structure of this sulfonium analog was established by chemical synthesis using the following methods: (I) condensation of sn-3-phosphatidic acid (dimyristoyl-, dipalmitoyl-, distearoyl- and dioleoyl-) with sulfocholine chloride in the presence of triisopropylbenzenesulfonylchloride in chloroform-pyridine (9:1); and (II) phosphorylation of 1,2-dipalmitoyl-sn-glycerol with monophenylphosphoryldichloridate followed by a reaction with sulfocholine in the presence of pyridine and finally removal of the blocking phenyl group by catalytic hydrogenolysis. The desired synthetic products were obtained in overall yields of 50-70% and 11% for methods (I) and II), respectively, and were characterized by elemental analyses; IR spectroscopy, NMR spectrometry and mass spectrometry; optical rotation; and TLC mobilities. Comparison of the synthetic analogs with the natural sulfolecithin showed them to be identical, except for the nature of the fatty acid chains, thus establishing the natural product as sn-3-phosphatidyl sulfocholine.