posted on 2003-12-26, 00:00authored byLauri Vares, Atanas V. Koulov, Bradley D. Smith
Short synthetic routes are described to produce structurally related phospholipids that are either
conformationally restricted or flexible. The conformationally restricted structures have a cyclopropyl
ring in the interfacial region of the phospholipid. The key synthetic step is a cyclopropanation
reaction between 2(5H)-furanone and a stabilized chloroallylic phosphonate anion. The synthetic
routes enable the incorporation of different polar headgroups as well as nonpolar tails at late stages
in the sequence. The phosphoethanolamine derivatives 1b and 2b readily form encapsulating
vesicles, however, dye leakage from vesicles composed of the restricted phospholipid 1b is
significantly slower than from vesicles composed of flexible analogue 2b. Physicochemical analyses
using 31P NMR, differential scanning calorimetry, fluorescence anisotropy, and Langmuir−Blodgett
films suggest that the decreased permeability of membranes composed of conformationally restricted
1b is due to its ability to pack more closely in a bilayer assembly.