Stearoyl paratoluenesulfonate. A powerful acylating agent for lipid synthesis

Phospholipids containing photoactivable groups in studies of biological membranes

Photoactivable carbene precursors, aryl diazirines and trifluorodiazopropionates, were incorporated synthetically into the omega-positions of fatty acids, which were used to synthesize phospholipids. Extensive intermolecular C--H insertion reactions were demonstrated by photolysis of liposomes prepared from the above phospholipids. Structural analysis of the cross-linked products showed that the predominant sites of cross-linking were in the expected positions within the bilayer. Studies on the topography of a number of membrane proteins using the above phospholipids were initiated. Cross-linking of the photoactivable phospholipids to membrane-embedded proteins, glycophorin A, cytochrome b5, and gramicidin A, was demonstrated.

Synthesis of glycerophospholipids

Recent advances in the synthesis of phosphatidic acids, phosphatidylethanolamines and phosphatidylcholines are described. Methods for the synthesis of some alkylacyl and alk-1-enylacyl analogues of the common diacylglycerophospholipids are also discussed. In addition, synthetic routes are described, that lead to unusual phospholipids such as compounds containing the polar group at position 2 of the glycerol moiety, glycerophospholipids containing alkanolamines of different chain lengths, and glycolphospholipids. All of the common glycerophospholipids can be prepared without the use of protecting groups. Major advances in phospholipid synthesis involve the application of novel phosphorylating agents and the use of cyclic intermediates. Although phosphatidylserines and phosphatidylthreonines as well as phosphatidylglycerols and cardiolipins can be prepared by chemical synthesis, further systematic studies are required to work out procedures that lead to these compounds in high yields.