Rose Bengal, a dye sensitizer, was found to be active as a visible light photoredox catalyst for the direct enantioselective α-alkylation of aldehydes in environmentally benign and simple conditions. Starting from a SOMO converse mechanism, the catalytic activity of the imidazolidinone organocatalyst was improved using an electrophilic cocatalyst. The resulting methodology and optimal conditions led to efficient and transition-metal-free direct photoredox organocatalysis.Scheme 1 Previous laboratory work showing the competitive pathways in the photo-oxidation of tertiary amines. † Electronic supplementary information (ESI) available: General procedures, experimental data, photosensitizers properties, spectroscopic data. See

Cationic nucleoside lipids based on a 3-nitropyrrole universal base were prepared from D-ribose using a straightforward chemical synthesis. Several studies including DLS, TEM and ethidium bromide (EthBr) assay demonstrated that these amphiphilic molecules form supramolecular organizations of nanometer size in aqueous solutions and are able to bind nucleic acids. siRNA knockdown experiments were performed with these nucleolipids and we observed protein knockdown activity similar to the siPORT NeoFX positive control. No significant cytotoxicity was found.Nucleolipids --amphiphiles possessing both nucleic acid recognition and lipophilic alkyl chains components--are emerging as both tools for constructing supramolecular assemblies and for nucleic acid delivery.(1-13) The area of nucleic acid delivery is particularly interesting, since gene delivery provides a mechanism to introduce new genes in cells for basic in vitro research experiments as well as to replace or supplement a defective or missing gene in a patient as part of a clinical therapy.(14-20) Consequently, synthetic lipids, as well as other DNA carriers such as calcium phosphate particles, dendrimers, or surface-mediated assemblies(21), are highly sought-after. Minimally toxic to cells, these lipids also afford high DNA or RNA transfection activity. Recently, we have reported the synthesis and transfection activity of a series of cationic and glycosylated nucleolipids which are both nontoxic and active DNA transfection agents. (11) (13) In an ongoing effort to expand the scope and properties of this family of lipids we are 1) synthesizing analogs where the thymine nucleobase is replaced by the synthetic 3-nitropyrrole universal base, and 2) evaluating the potential of these nucleolipids for siRNA delivery. Herein, we report the synthesis, physico-chemical properties, and siRNA transfection efficiency of a universal-base nucleolipid, the tosylate salt of 1-(2', 3'-dioleyl-5'-trimethylammonium-(α,β)-D-ribofuranosyl)-3-nitropyrrole.Contact : mgrin@bu.edu or camplo@univmed.fr. The target nucleolipid, 7, is shown in Figure 1, which possesses three key components: a quaternized amine at the 5' position, two oleic acid chains linked at the 2' and 3' positions, and a 3-nitropyrrole attached at the anomeric position. The cationic charge is responsible for electrostatic binding to the nucleic acids and the oleyl chains contribute to stabilization of the resulting nucleic acid-nucleolipid assembly through hydrophobic chain-chain interactions. The 3-nitropyrrole, which is perhaps the best characterized universal base analogue, was introduced to circumvent the restrictive hydrogen bonding pattern controlling typical purine-pyrimidine hydrogen motifs by incorporating the weakly hydrogen bonding nitro substituent.(22-24) It is known that the 3-nitropyrrole group can form complementary base-pairs with all four natural bases without significantly destabilizing neighboring base-pair interactions. As a result, it has been used for diverse applications including hybri...