Synthesis of unnatural C-nucleosides for DNA-based catalysis.
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DNA based catalysis is a developing area in organic chemistry. It has been shown that DNA can not only increase the rates of reactions which occur in its presence but the inherent chirality of DNA can be transferred to the products of reactions which take place within the chiral environment it provides. We have synthesised an artificial C-nucleoside capable of metal coordination which can thus facilitate Lewis acid catalysis. The incorporation of this nucleotide into an artificial DNA sequence creates a novel system for asymmetric DNA based catalysis.
Post-synthetic modification of DNA allows its functionalisation. That is, the carrying out of chemical transformations on complete oligonucleotide species. In a second approach to asymmetric DNA based catalysis, an artificial DNA fragment has been prepared incorporating a synthetic monomer which comprises a terminal alkyne. Subsequent functionalisation of this alkyne by cycloaddition with an azide species put in place an organocatalyst moiety creating a further novel system for asymmetric DNA based catalysis.
The amination of aliphatic C-H bonds is a selective method for efficient preparation of amines. One of the most general and direct methods within this category for installing amino groups is the metal mediated nitrene insertion reaction and these nitrenes are often generated from azides. Chiral sulfonyl azides prepared by transformation of chiral sulfonic acid precursors could undergo similar reactions. The proposed photochemical conversion of enantiopure sulfonyl azides to cyclic sulfonamides, via nitrene intermediates, represents a mild metal free method for the functionalisation of aliphatic C-H bonds.