An unprecendented direct alkylation of unfunctionalized allylic/benzylic sp3 C–H bonds via photoredox induced radical cation deprotonation is disclosed.

Polyphenols are bioactive natural products that appear to act against a wide range of pathologies. Mechanisms of activity have not been established, but recent studies have suggested that some polyphenols bind to membranes. We examined the interaction between lipid bilayers and three structurally diverse polyphenols. We hypothesized that features of the polyphenols such as polarity, molecular size, molecular geometry, and number and arrangement of phenol hydroxyl groups would determine the tendency to interact with the bilayer. We examined a mixed polyphenol, (−) epigallocatechin gallate (EGCg); a proanthocyanidin trimer comprising catechin-(4→8)-catechin-(4→8)-catechin (cat3); and a hydrolysable tannin, 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose (PGG). These polyphenols were incorporated at different levels into 2H labeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) multi-lamellar vesicles (MLVs). 31P and 2H solid-state NMR experiments were performed to determine the dynamics of the headgroup region and the hydrophobic acyl chain region of the lipid bilayer upon addition of polyphenols. The chemical shift anisotropy (CSA) width of the 31P NMR spectra decreased upon addition of polyphenols. Addition of PGG induces a dramatic reduction on the CSA width compared with the control lipid bilayer sample, while addition of cat3 barely reduces the CSA width. The 2H quadupolar splitting of the lipids also decreased upon addition of polyphenols. At the same concentration, PGG substantially reduced the quadrupolar splitting while cat3 barely reduced it when compared with the control sample. By calculating the order parameters of the acyl chain region of the lipid bilayer, we concluded that the hydrophobic part of the lipid bilayer was perturbed by PGG while cat3 did not cause large perturbations. The data suggest that the polarity of the polyphenols affects the interaction between tannins and membranes. The interactions may relate to the biological activities of polyphenols.

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