Synthesis of oligoribonucleotides with sequences identical to the nucleation region of Tobacco Mosaic Virus RNA: Preparation of AAG, AAGAAG and AAGAAGUUG via phosphotriester methods

Advancement of the Cleavage Methods of Carbohydrate-derived Isopropylidene and Cyclohexylidene Ketals

Abstract:

Carbohydrates, amino acids, and nucleosides, the fundamental building blocks of complex biomolecules in nature, are essential starting materials for the fabrication of natural and unnatural structural entities, which necessitate the masking and demasking of various functional groups with the utmost chemoselectivity, mildness, and efficiency to avoid unintended bond breaking and formation, as well as associated reactions. Ketals, benzylidene, methoxymethyl, p-methoxybenzyl, silyl ethers, trityl, tert-butyl carbamate, and other functional groups are widely used in modern organic synthesis. In carbohydrate chemistry, the commonly used protecting functionality of isopropylidene and cyclohexylidene ketals necessitates effective methods for selective cleavage. This review summarises different methods for deblocking isopropylidene and cyclohexylidene ketals using inorganic acids, Lewis acid, silica-supported inorganic acids, Amberlite-120 (H+) resin, phosphotungstic acid, Nafion-H, NaBArF4.2H2O, montmorillonite clay, Dowex 50W-X8, camphorsulphonic acid (CSA), ceric ammonium nitrate, molecular iodine, ionic liquids, zeolites and so on.

Protection of 2'-hydroxy functions of ribonucleosides

The main purpose of this article is to discuss 2'-protection in the context of effective oligoribonucleotide synthesis. Emphasis is placed on the 2'-protecting groups of choice in the synthesis of oligo-and polyribonucleotides, and the requirements that a protective group must satisfy to become the 2'-hydroxyl-protecting group of choice. Finally, the unit discusses the issue of 2'-O-acyl and 2'-O-silyl group migration to the 3'-hydroxy function of ribonucleosides during protection, along with the consequences of the conditions used for their removal on the stability of internucleotide linkages.

Synthesis of DNA Oligomers Possessing a Covalently Cross-Linked Watson-Crick Base Pair Model

Building bridges: A feasible solid-phase synthesis of antiparallel n-, h-, and H-type DNA oligomers has been demonstrated. The oligomers possess a CH₂ -bridged base-pair model that should be conformationally flexible, even after base pairing.