Analogs of natural lipids. VII. Synthesis of cyclopentanoid analogs of phosphatidylcholine

A series of six analogs of phosphatidylcholine (lecithin) has been synthesized, in which the conformational mobility of the backbone is restricted. The analogs are derivatives of the three diastereoisomeric cyclopentane-1,2,3-triols and were obtained by triisopropylbenzenesulfonyl chloride-mediated condensation of isomers of dipalmitoylcyclopentanetriol phosphate (cyclopentano-phosphatidic acid) with choline tosylate. The cyclopentano-lecithins obtained include the following: 1,2,3/0-(1P); 1,2,3/0-(2P); 1,2/3-(1P); 1,2/3-(3P); 1,3/2-(1P); 1,3/2-(2P). The two -2P derivatives are mesoforms while the other four derivatives are DL-pairs. Each lecithin analog has been obtained as a stable microcrystalline solid. Elemental analysis indicates that the compounds are hydrated; the data were consistent with the presence of either one, or in two instances, of one-half molecule of water of hydration. The infrared spectra, melting behavior, and chromatographic mobility of each of the analogs resembled those obtained for dipalmitoyllecithin, but the influence upon physical properties of stereochemical differences among the analogs was observed throughout the series.