from a variety of lipids including but not limited to amphipathic lipids such as phosphatidylcholines sphingomyelins phosphatidylethanolamines phophatidylcholines cardiolipins phosphatidylserines phosphatidylglycerols phosphatidic acids phosphatidylinositols diacyl trimethylammonium propanes diacyl dimethylammonium propanes and stearylamine neutral lipids such as triglycerides and combinations thereof they may either contain cholesterol or may be cholesterol free from formula i it is evident that some of the compounds of the invention may have one or more asymmetric carbon atoms in their structure it is intended that the present invention include within its scope the stereochemically pure isomeric forms of the compounds as well as their racemates stereochemically pure isomeric forms may be obtained by the application of art known principles diastereoisomers may be separated by physical separation methods such as fractional crystallization and chromatographic techniques and enantiomers may be separated from each other by the selective crystallization of the diastereomeric salts with optically active acids or bases or by chiral chromatography pure stereoisomers may also be prepared synthetically from appropriate stereochemically pure starting materials or by using stereoselective reactions some of the compounds of the present invention may have trans and cis isomers in addition where the processes for the preparation of the compounds according to the invention give rise to mixture of stereoisomers these isomers may be separated by conventional techniques such as preparative chromatography the compounds may be prepared as a single stereoisomer or in racemic form as a mixture of some possible stereoisomers the non racemic forms may be obtained by either synthesis or resolution the compounds may for example be resolved into their component enantiomers by standard techniques such as the formation of.