Design, Synthesis, and Self-Assembly of Amphiphilic 1,4-Dihydropyridines Containing Branched Ester Moieties

Amphiphilic cationic lipids based on the 1,4-dihydropyridine (1,4-DHP) scaffold represent a versatile platform for the development of self-assembling delivery systems. In this work, a series of ten new amphiphilic 1,4-DHP derivatives bearing branched ester substituents at the 3,5-positions and quaternized cationic groups at the 2,6-positions were designed and synthesized. The effect of branched ester chain length and branching on nanoparticle formation was investigated. The self-assembling properties of the synthesized amphiphiles were evaluated by dynamic light scattering using an ethanol injection method. All compounds formed positively charged nanoparticles with hydrodynamic diameters ranging from 52 to 439 nm and polydispersity index from 0.194 to 0.452. Amphiphiles 14b–17b with 2-hexyldecyl substituents formed smaller particles, with an average diameter below 100 nm. Several derivatives exhibited good stability over a 14-day storage period at room temperature. To clarify structure–property relationships, lipophilicity (AlogP), polar surface area (PSA), and pKa values were calculated using Schrödinger computational tools. The compounds displayed high lipophilicity AlogP 8.98–19.32, while PSA values remained within a narrow range. The calculated pKa values ranged from 7.20 to 10.99. The results demonstrate that both the length and architecture of branched ester chains significantly influence nanoparticle size, homogeneity, and stability, highlighting branched-chain 1,4-DHP amphiphiles as promising synthetic lipid candidates for further development of delivery systems after evaluation of biological properties.