Editing Synthesis of Lipids (section)

== Synthesis of DOTMA  ==

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[[Image:DOTMA synthesis.png]] 

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DOTMA Synthesis and Liposome Preparation. DOTMA<br>{N-[1-(2,3,-dioleyloxy)propyl]-N,N,N-trimethylammonium<br>chloride} was prepared as outlined in Fig. 1. A mixture of<br>3-(dimethylamino)-1,2-propanediol (Aldrich; 1.19 g, 10<br>mmol), potassium tert-butoxide (3.36 g, 30 mmol), and oleyl<br>p-toluenesulfonate (12.7 g, 30 mmol) in xylenes (50 ml) was<br>stirred at room temperature and reduced pressure (30 torr; 1<br>torr = 133 Pa) for 30 min and then was heated to 50TC with<br>stirring for an additional 15 min. The reaction vessel was<br>purged with nitrogen, and the mixture was heated to reflux<br>(-4140'C) for 3 hr. After cooling, the reaction mixture was<br>diluted with hexane (100 ml), and the resulting solution was<br>extracted with water (twice, 50 ml each). The organic layer<br>was concentrated, and the residue was chromatographed<br>over silica gel by elution with a mixture of hexanes and<br>diethyl ether (1:2) to afford the intermediate 2,3-dioleyloxy-<br>1-(dimethylamino)propane as a colorless oil. Quaternization<br>was carried out by condensation of methyl chloride (50 ml)<br>into a Parr pressure apparatus cooled to -78°C and contain-<br>ing this compound (10 g). The sealed vessel was heated<br>behind a safety shield at 70°C for 48 hr. After cooling to 0°C,<br>the reaction vessel was opened, and the excess methyl<br>chloride was allowed to evaporate under a stream of nitrogen<br>in a well-ventilated hood. The crude residue was recrystal-<br>lized from acetonitrile to afford DOTMA as an off-white<br>solid, mp 35-38°C. Full details of the synthesis of DOTMA<br>and analogs will be published elsewhere (T.R.G. and P.L.F.).<br>A solution of dioleoyl phosphatidylethanolamine (PtdEtn;<br>10 mg) and DOTMA (10 mg) in chloroform (1 ml) was<br>evaporated to dryness under a stream of nitrogen, and<br>residual solvent was removed under vacuum overnight.<br>Liposomes were prepared by resuspending the lipids in<br>deionized water (2 ml) and sonicating to clarity in a closed<br>vial. Sterile preparations of liposomes are stable for at least<br>6 months at 4°C. 

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