Application of Phosphoramidate ProTide Technology Significantly Improves Antiviral Potency of Carbocyclic Adenosine Derivatives

Abstract

We report the application of phosphoramidate pronucleotide (ProTide) technology to the antiviral agent carbocyclic L-d4A (L-Cd4A). The phenyl methyl alaninyl parent ProTide of L-Cd4A was prepared by Grignard-mediated phosphorochloridate reaction and resulted in a compound with significantly improved anti-HIV (2600-fold) and HBV activity. We describe modifications of the aryl, ester, and amino acid regions of the ProTide and how these changes affect antiviral activity and metabolic stability. Separate and distinct SARs were noted for HIV and HBV. Additionally, ProTides were prepared from the D-nucleoside D-Cd4A and the dideoxy analogues L-CddA and D-CddA. These compounds showed more modest potency improvements over the parent drug. In conclusion, the ProTide approach is highly successful when applied to L-Cd4A with potency improvements in vitro as high as 9000-fold against HIV. With a view to preclinical candidate selection we carried out metabolic stability studies using cynomolgus monkey liver and intestinal S9 fractions.

First Example of Phosphoramidate Approach Applied to a 4‘-Substituted Purine Nucleoside (4‘-Azidoadenosine): Conversion of an Inactive Nucleoside to a Submicromolar Compound versus Hepatitis C Virus

“…The elimination of HI was performed in the same conditions described above. The key step was the synthesis of the epoxide (14) and the subsequent ring opening reaction. In order to avoid N1-oxidation with DMDO, it was necessary to acylate the 6-NH 2 group (13).…”

“…In order to avoid N1-oxidation with DMDO, it was necessary to acylate the 6-NH 2 group (13). The unsaturated derivative of adenosine (13) was converted to the corresponding epoxide (14) in the presence of 1 M solution of dimethoxydioxirane, which has been previously reported as stereoselective reagent for such epoxidation reactions. 23 The ring opening reaction was then performed in the presence of a Lewis Acid (tin tetrachloride) and azidotrimethylsilane.…”

Synthesis and Evaluation of 2,6-Modified Purine 2′-C-Methyl Ribonucleosides as Inhibitors of HCV Replication

“…Therefore, in order to overcome the often rate-limiting first phosphorylation step and improve the antiviral activity of our nucleoside analogues, we prepared their corresponding monophosphate McGuigantype prodrugs. 12 The synthesis of phosphoramidates 31−46 was performed following the Uchiyama procedure by reacting the nucleosides 10−12, 14,15,17,18,20,22,23,25,26,28, and 29 with chlorophosphoramidate 30 13 in the presence of N-methylimidazole (Scheme 4). 14,15 It is noteworthy that the use of acetonitrile as a cosolvent improved the solubility of certain nucleosides leading to better overall yields.…”

“…12 The synthesis of phosphoramidates 31−46 was performed following the Uchiyama procedure by reacting the nucleosides 10−12, 14,15,17,18,20,22,23,25,26,28, and 29 with chlorophosphoramidate 30 13 in the presence of N-methylimidazole (Scheme 4). 14,15 It is noteworthy that the use of acetonitrile as a cosolvent improved the solubility of certain nucleosides leading to better overall yields. Attempts to prepare the 2-aminooxypurine nucleoside prodrugs by Cbz removal of compounds 38 and 40 were not successful and instead afforded the isoguanosine derivatives 39 and 41.…”

Synthesis and Biological Evaluation of LNA Phosphoramidates

“…To solve this problem lipophilic monophosphate prodrugs such as simple phosphate esters (Adefovir dipivoxil), CycloSal, [3] SATE, [4] and phosphoramidates [5,6] have been prepared. Due to the many promising prospects of nucleotide prodrugs research within the field is continuously growing.…”