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Choline phospholipids can be conveniently synthesized by reaction of a lipophilic alcohol, such as diacylglycerol, with 2-bromoethyl dichlorophosphate followed by nucleophilic displacement of the bromine with trimethylamine. We found that the low yields often encountered in the initial phosphorylation step are particularly due to exchange of both chlorines for alkoxy functions (triester formation) and to chlorination of the alcohol by 2-bromoethyl dichlorophosphate. However, these drawbacks can be overcome by proper choice of the reaction medium and by optimizing other reaction conditions. The procedure described is efficient and most versatile, and it lends itself to the preparation of a wide range of choline phospholipids containing a glycerol, diol, or long-chain alkyl backbone and bearing various aliphatic functions. Proton and carbon-13 nuclear magnetic resonance spectroscopy proved useful in establishing the homogeneity and structures of the synthetic intermediates and byproducts and of the choline phospholipids synthesized.

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Figure 2. Newman projections of a concerted reaction.could be separated from an almost equal quantity of an inseparable mixture of 2b and acetates lg and lh. The 300-MHz NMR analyses clearly showed that >50% of the mixed fraction obtained from la and <50% of the mixed fraction from lb were cyclopropyl acetates lg and lh. Time and Temperature Studies of the Acetolysis Reaction.Solutions of 3 pL of compound in 10 µL of glacial acetic acid were submitted to various temperature and time intervals. They were then quenched in aqueous sodium bicarbonate solution, extracted, and analyzed by thin-layer chromatography or analytical highpressure LC using a suitable hexane-ether elution system. In this way it was found that at 25 °C la and lb were stable to glacial acetic acid for up to 8 h.The product ratio of acetates obtained by heating either la or lb in glacial acetic acid at 110-11 °C over intervals between 10 min and 16 h were not significantly different.The products 2a and 2b were not interchanged significantly over a period of 24 h at 110 °C in glacial acetic acid.(U)-3-Ethylidenecyclohexanol 3,5-Dinitrobenzoate. A solution of 290 mg of 2a and 180 mg of potassium hydroxide in 4 mL of methanol was refluxed under nitrogen for 1.5 h. The reaction mixture was concentrated to dryness and treated with water. The product was extracted into ether, washed with water (4X), dried (MgS04), and isolated as a liquid. This material was eluted through 18 g of silica gel to give 88 mg of 3-ethylidenecyclohexanol: