Synthesis, Hydrolysis, and Protonation-Promoted Intramolecular Reductive Breakdown of Potential NRTIs: Stavudine α-P-Borano-γ-P-N-L-tryptophanyltriphosphates.
Phosphorus-modified prodrugs of dideoxynucleoside triphosphates (ddNTPs) have shown promise as pronucleotide strategies for improving antiviral activity compared to their parent dideoxynucleosides. Borane modified NTPs offer a promising choice as nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). However, the availability of α-P-borano-γ-P-substituted NTP analogs remains limited due to challenges with synthesis and purification. Here, we report the chemical synthesis and stability of a new potential class of NRTI prodrugs: stavudine (d4T) 5'-α-P-borano-γ-P-N-L-tryptophanyltriphosphates. One-pot synthesis of these compounds was achieved via a modified cyclic trimetaphosphate approach. Pure Rp and Sp diastereomers were obtained after HPLC separation. Based on LC-MS analysis, we report degradation pathways, half-lives (5-36 days) and mechanisms arising from structural differences to generate the corresponding borano tri- and di-phosphates, and H-phosphonate, via several parallel routes in buffer at physiologically relevant pH and temperature. Here, the major hydrolysis products, d4T α-P-boranotriphosphate Rp and Sp isomers, were isolated by HPLC and identified with spectral data. We first propose that one of the major degradation products, d4T H-phosphonate, was generated from the d4T pronucleotides via a protonation-promoted intramolecular reduction followed by a second step nucleophilic attack. This report could provide valuable information for pronucleotide-based drug design in terms of selective release of target nucleotides.
Shaw Department of Chemistry, Duke University, Durham, NC 27708, USA. zhihong.xu@duke.edu.
Zhihong
Z
Xu
Shaw Department of Chemistry, Duke University, Durham, NC 27708, USA. barbara.r.shaw@duke.edu.
Barbara
B
Ramsay Shaw
D001880:Boranes / Q000138:chemical synthesis; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D010084:Oxidation-Reduction; D011122:Polyphosphates / Q000138:chemical synthesis; D011355:Prodrugs / Q000138:chemical synthesis*; D018894:Reverse Transcriptase Inhibitors / Q000138:chemical synthesis*; D018119:Stavudine / Q000031:analogs & derivatives* / Q000138:chemical synthesis*; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000138:chemical synthesis*
D001880:Boranes; D011122:Polyphosphates; D011355:Prodrugs; D018894:Reverse Transcriptase Inhibitors; D014364:Tryptophan; D018119:Stavudine
boron chemistry; d4T boranotriphosphate analog; intramolecular reduction; mechanism; pronucleotide; stability