Observations on Protecting Groups in the Synthesis of Mono- and Triphosphates of Amino Alcohols

Abstract

Natural and modified nucleoside polyphosphates are indispensable tools in modern biological investigations. Their applications include but are not limited to polymerase chain reactions (PCR), single nucleotide polymorphism (SNP) detection, DNA/RNA labelling, non-specific mutagenesis, and DNA-sequencing including single molecule real time sequencing. It is known that the terminal phosphate labeled nucleoside 5 polyphosphates (n1⁄4 2-4, Figure 1) are better substrates for RNAand DNA-polymerases than c-labelled nucleoside 5 -triphosphates. One of the approaches to obtain derivatives like those shown in Figure 1, where X cannot be phosphorylated directly, includes the insertion of an intermediate aminoalkyl linker tethered to the terminal phosphate by a stable phosphoroester bond and coupling of two phosphorylated blocks to form a disubstituted polyphosphate chain. This may provide a wide variety of derivatives conjugated with fluorescent labels based on commercially available carboxyl containing dyes. Recently, we applied this strategy to the synthesis of a number of novel ADP conjugates, potential inhibitors of poly(ADPribosyl)polymerase 1. In that work, AMP and monophosphorylated amino alcohols protected at the amino group were coupled to give disubstituted pyrophosphates. Unlike pyrophosphate linkage formation, there are different strategies to obtain the linear polyphosphates by coupling two phosphorylated blocks. Among them, coupling that involves monoand triphosphate derivatives is more attractive due to the relative availability of parent monoand triphosphorylated species in contrast to diphosphates. Currently, there are several methods for the monoand triphosphorylation of alcohols including nucleoside derivatives. To provide the selective O-phosphorylation of amino alcohols containing aliphatic amino groups it is necessary to protect the