Oxetane nucleosides with fluorine and azide substitutents: nucleophilic displacements on an oxetane ring

A mini-review on synthesis and antiviral activity of natural product oxetanocin A derivatives

Oxetanocin A (Oxt-A), a novel oxetanosyl N-glycoside nucleoside, was isolated from Bacillus megaterium in 1986. It carries an oxetane ring on the sugar moiety of the nucleoside scaffold, which contributes to differences in its structure from those of common tetrahydrofuranyl-based nucleosides. In view of the unique 3D-spatial framework, the complete synthesis of Oxt-A has been achieved by multiple research groups. The pharmacological properties of this natural product have also been broadly investigated by pharmacists and chemists since its discovery. Notably, the potential antiviral effect of Oxt-A has captured attention of researchers in the field of antiviral agent development. Furthermore, epidemic outbreaks caused by viruses have been stimulating the preparation and modification of various Oxt-A analogs over the past few decades. However, none of the studies have overviewed the antiviral efficacies of this naturally occurring scaffold yet. Thus, the present review summarizes the synthesis, structural modification, and antiviral activities of Oxt-A and its derivatives. We believe that these comprehensive descriptions will provide a novel perspective for the discovery of antivirus drugs with well-improved performance and pave newer paths for combating sudden public health issues triggered by viruses in the future.

Decarboxylative Halogenation of Organic Compounds

Decarboxylative halogenation, or halodecarboxylation, represents one of the fundamental key methods for the synthesis of ubiquitous organic halides. The method is based on conversion of carboxylic acids to the corresponding organic halides via selective cleavage of a carbon-carbon bond between the skeleton of the molecule and the carboxylic group and the liberation of carbon dioxide. In this review, we discuss and analyze major approaches for the conversion of alkanoic, alkenoic, acetylenic, and (hetero)aromatic acids to the corresponding alkyl, alkenyl, alkynyl, and (hetero)aryl halides. These methods include the preparation of families of valuable organic iodides, bromides, chlorides, and fluorides. The historic and modern methods for halodecarboxylation reactions are broadly discussed, including analysis of their advantages and drawbacks. We critically address the features, reaction selectivity, substrate scopes, and limitations of the approaches. In the available cases, mechanistic details of the reactions are presented, and the generality and uniqueness of the different mechanistic pathways are highlighted. The challenges, opportunities, and future directions in the field of decarboxylative halogenation are provided.

Square sugars: challenges and synthetic strategies

The synthesis of square sugars requires innovative strategies based on efficient stereoselective methodologies, from organocatalysis to metal carbene insertion.

Synthesis and absolute configuration assignment of albucidin: a late-stage reductive deiodination by visible light photocatalysis

The total synthesis and absolute configuration assignment of albucidin might pave the way for synthetic and medicinal chemists for further research on this type of bioactive molecule.

Skeletal rearrangements resulting from reactions of 1,6:2,3- and 1,6:3,4-dianhydro-β-D-hexopyranoses with diethylaminosulphur trifluoride

A complete series of eight 1,6:2,3- and 1,6:3,4-dianhydro-β-D-hexopyranoses were subjected to fluorination with DAST. The 1,6:3,4-dianhydropyranoses yielded solely products of skeletal rearrangement resulting from migration of the tetrahydropyran oxygen (educts of D-altro and D-talo configuration) or of the 1,6-anhydro bridge oxygen (D-allo, D-galacto). The major products yielded by the 1,6:2,3-dianhydropyranoses were compounds arising from nucleophilic substitution, with configuration at C4 either retained (D-talo, D-gulo) or inverted (D-manno), or from C6 migration (D-allo). The minor products in the 1,6:2,3-series resulted from migration of the tetrahydropyran oxygen (D-gulo) or the oxirane oxygen (D-manno), or from nucleophilic substitution with retention of configuration (D-manno). The structure of most of the rearranged products was verified by X-ray crystallography.

Novel nucleoside strategies for anti-HIV and anti-HSV therapy

This mini-review describes the structure-activity relationships of several series of new nucleoside analogues. It also points to the possibilities of finding new molecular modifications which could lead to antivirals with activity both against human immunodeficiency viruses (HIV) and herpesviruses.