Polymorphism of monolayer lipid membrane structures made from unsymmetrical bolaamphiphiles

The crystal structures of synthetic unsymmetrical 1-glucosamide- and 1-galactosamide bolaamphiphiles, 13-[(β-d-glucopyranosyl)carbamoyl]tridecanoic acid (1) and 15-[(β-d-galactopyranosyl)carbamoyl]pentadecanoic acid (2), respectively, were elucidated by single-crystal X-ray analysis. The space group for 1 is P21, Z = 2 with cell dimensions: a = 8.6816(9), b = 4.8578(5), c = 26.250(3) Å, β = 91.460(2)°; that for 2P21, Z = 2 with cell dimensions: a = 4.90(1), b = 40.139(1), 6.289(1) Å, β = 106.48(1)°. The glucopyranosyl and galactopyranosyl rings in 1 and 2, respectively, take a 4C1 chair conformation. In the crystal lattice, the 1-glucosamide 1 forms a symmetrical monolayer lipid membrane (MLM) structure in which the molecules are packed in an antiparallel fashion, while 1-galactosamide 2 has an unsymmetrical MLM with parallel molecular packing. The stereochemistry of the sugar hydroxy group proved to affect their hydrogen-bonding networks and induce the polymorphism of the MLM.

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