Chemically Modified Nucleic Acid Synthesis

A controlled pore glass support (CPG) derivatized with 2′-O-methyl-A, 2′-O-methyl-G, deoxythymidine, 5′,N-protected 2′-O-methylribo- (A, C, G, or U), 2′-O-TBDMS-ribo (A, C, G, or U) and deoxyribo (dT) phosphoramidites, 2-[2-(4,4’-dimethoxytrityloxy)ethylsulfonyl]ethyl-(2-cyanoethyl)-(N,N-diisopropyl)-phosphoramidite (CPR, Chemical Phosphorylation Reagent) were purchased from Glen Research Inc. (Sterling, VA, USA). Propargylamine, 1,6-diaminohexane, (pyrene-1-yl-methyl)amine hydrochloride, p-anisic (4-methoxybenzoic) acid, N,N′-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole hydrate (HOBt), N,N-diisopropylethylamine (DIPEA), α-GalNac-azide, and 1 M TBAF solution in THF were purchased from Sigma-Aldrich (St. Louis, MO, USA), N-Boc-1,6-diaminohexane hydrochloride and ethoxytrimethylsilane were obtained from Alfa Aesar (Heysham, UK); cholesterol chloroformate and oleylamine were obtained from Acros Organics (Geel, Belgium); 3-amino-1-propanol, triphenylphosphine (PPh₃), and 2,2′-dipyridyl disulfide ((PyS)₂) were obtained from Fluka (St. Louis, MO, USA). FAM-NHS, FAM-azide, 10 mM Cu(II)-TBTA Stock in 55% DMSO, and ascorbic acid were purchased from Lumiprobe (Moscow, Russia). All solvents (THF, DMSO, CH₃CN (various vendors)) were dried by 3 Å molecular sieves or by distillation and stored over CaH₂. Small molecule ligands were analyzed by thin-layer chromatography (TLC) using DC-Alufolien Kieselgel 60 F₂₅₄ plates (Merck, Darmstadt, Germany) at 254 nm ultraviolet light.