Synthesis of the tBuSATE pronucleotide of AZT by two different synthetic approaches

Chemistry of bisSATE mononucleotide prodrugs

On the basis of AZT as a nucleosidic model, the protocols herein describe the synthesis of various bis(S-acyl-2-thioethyl) phosphotriester derivatives. These compounds, bearing transient phosphate-protecting groups, were designed to liberate the corresponding 5'-mononucleotide inside the cell through an esterase-mediated activation process. Two synthetic approaches are presented using either phosphoramidite intermediates or esterification of a nucleoside 5'-monophosphate.

Synthetic approaches to a mononucleotide prodrug of cytarabine

Synthetic pathways to a mononucleotide prodrug of cytarabine (Ara-C) bearing S-pivaloyl-2-thioethyl (tBuSATE) groups, as biolabile phosphate protections, are reported. Using a common phosphoramidite approach, two different kinds of nucleoside protecting groups have been investigated. During this study, we observed an intermolecular migration of the Boc protecting group in the course of the tert-butyldimethylsilyl ether cleavage using tetrabutyl ammonium fluoride.

Influence of a Calpha-substitution on the S-pivaloyl-2-thioethyl chain on the anti-HIV activity and stability of the resulting zidovudine mononucleoside phosphotriester

We report the synthesis, in vitro anti-HIV-1 activity and stability study of a mononucleoside phosphotriester derivative of 3'-azido-2',3'-dideoxythymidine (AZT) bearing a new biolabile phosphate-protection, namely S-pivaloyl-2-thioisopropyl (tBuSATP). This transient protection was characterized by the presence of a methyl substituent at the Calpha-position of the previously described S-pivaloyl-2-thioethyl (tBuSATE) group. Results demonstrated that the new phosphotriester entity was able to deliver selectively the corresponding 5'-mononucleotide within the infected cells. The introduction of a methyl group at the Calpha-position of the tBuSATE chain decreased the rate of this delivery.