Synthesis of 8-Bromo- and 8-Azido-2′-deoxyadenosine-5′-O-(1-thiotriphosphate)

Synthesis of two 8-[(anthraquinone-2-yl)-linked]-2'-deoxyadenosine 3'-benzyl hydrogen phosphates for studies of photoinduced hole transport in DNA

The challenge in working with anthraquinone-2'-deoxyadenosine (AQ-dA) conjugates is that they are insoluble in water and only sparingly soluble in most organic solvents. However, water-soluble AQ-dA conjugates with short linkers are required for study of their electrochemical and intramolecular electron transfer properties in this solvent prior to their use in laser kinetics investigations of photoinduced hole (cation) transport in DNA. This article first describes the synthesis of a water-soluble, ethynyl-linked AQ-dA conjugate, 8-[(anthraquinone-2-yl)ethynyl]-2'-deoxyadenosine 3'-benzyl hydrogen phosphate, based on initial formation of a 5'-O-(4,4'-dimethoxytrityl) (5'-O-DMTr) intermediate. Because intended H2 over Pd/C reduction of the ethynyl linker in 5'-O-DMTr-protected 2'-deoxyadenosines cleaves the DMTr protecting group and precipitates multiple side products, this work also describes the synthesis of an ethylenyl-linked AQ-dA conjugate, 8-[2-(anthraquinone-2-yl)ethyl]-2'-deoxyadenosine 3'-benzyl hydrogen phosphate, starting with a 5'-O-tert-butyldiphenylsilyl protecting group.

Enhancement of nucleoside cytotoxicity through nucleotide prodrugs

A common reason for the lack of cytotoxicity of certain nucleosides is thought to be their inability to be initially activated to the monophosphate level by a nucleoside kinase or other activating enzyme. In a search for other nucleosides that might be worthwhile anticancer agents, we have begun to examine the utilization of monophosphate prodrugs in order to explore whether any enhanced cytotoxicity might be found for the prodrugs of candidate nucleosides that have little or no cytotoxicity. To that end, 5'-bis(pivaloyloxymethyl) phosphate prodrugs of two weakly cytotoxic compounds, 8-aza-2'-deoxyadenosine (5) and 8-bromo-2'-deoxyadenosine (9), have been prepared. These prodrugs (8 and 12) were examined for their cytotoxicity in CEM cells and were found to possess significantly enhanced cytotoxicity when compared with the corresponding parent nucleosides. Further cell culture experiments were conducted to gain insight into the mechanisms of cytotoxicity of these two prodrugs, and those data are reported.