Addition of halogenated acetic acids to vinyl ketones. Nuclear magnetic resonance study of the kinetics

Sequence-Defined Cationic Lipo-Oligomers Containing Unsaturated Fatty Acids for Transfection

Sequence-defined cationic lipo-oligomers containing unsaturated fatty acids are potent nucleic acid carriers that are produced by solid-phase supported synthesis. However, the trifluoroacetic acid (TFA)-mediated removal of acid-labile protecting groups and cleavage from the resin can be accompanied by side products caused by an addition of TFA to the double bonds of unsaturated fatty acids. These TFA adducts are converted into hydroxylated derivatives under aqueous conditions. Here we describe an optimized cleavage protocol (precooling cleavage solution to 4 °C, 20 min cleavage at 22 °C), which minimizes TFA adduct formation, retains the unsaturated hydrocarbon chain character, and ensures high yields of the synthesis.

A nuclear magnetic double resonance study of N-beta-bis-(beta'-chloroethyl) phosphonylethyl-DL-phenylalanine

Studies were carried out on the effect of decoupling, deuterium labeling, concentration, temperature, and solvent media on the NMR parameters of the vinyl phosphonate adduct of phenylalanine, C6H5CH2CH(COO-)NH2+CH2CH2PO(OCH2CH2C1)2. The results permit assignments of chemical shifts and coupling constants to the various protons of this molecule which contains unique structural features. The NH2+-CH2-protons are deshielded by more than 1 ppm than the CH2-PO-protons. The -OCH2-protons are nonequivalent exhibiting a fine split. Possible sources of the fine split include NH...O=P hydrogen bonding. The deuterium-labeling method should be applicable for synthesizing deuterium-and tritium-labeled crosslinked amino acids such as lysinoalanine and lanthionine and demonstrating analgous dehydroalanine-alpha-amino group-crosslinking.