| Abstract
| - Short synthetic routes are described to produce structurally related phospholipids that are eitherconformationally restricted or flexible. The conformationally restricted structures have a cyclopropylring in the interfacial region of the phospholipid. The key synthetic step is a cyclopropanationreaction between 2(5H)-furanone and a stabilized chloroallylic phosphonate anion. The syntheticroutes enable the incorporation of different polar headgroups as well as nonpolar tails at late stagesin the sequence. The phosphoethanolamine derivatives 1b and 2b readily form encapsulatingvesicles, however, dye leakage from vesicles composed of the restricted phospholipid 1b issignificantly slower than from vesicles composed of flexible analogue 2b. Physicochemical analysesusing 31P NMR, differential scanning calorimetry, fluorescence anisotropy, and Langmuir−Blodgettfilms suggest that the decreased permeability of membranes composed of conformationally restricted1b is due to its ability to pack more closely in a bilayer assembly.
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