Stereoselective synthesis of PSI-352938: a β-D-2'-deoxy-2'-α-fluoro-2'-β-C-methyl-3',5'-cyclic phosphate nucleotide prodrug for the treatment of HCV. 2011

P Ganapati Reddy, and Byoung-Kwon Chun, and Hai-Ren Zhang, and Suguna Rachakonda, and Bruce S Ross, and Michael J Sofia
Pharmasset, Inc., 303A College Road East, Princeton, New Jersey 08540, United States.

PSI-352938 is a novel 2'-deoxy-2'-α-fluoro-2'-β-C-methyl 3',5'-cyclic phosphate nucleotide prodrug currently under investigation for the treatment of hepatitis C virus (HCV) infection. PSI-352938 demonstrated superior characteristics in vitro that include broad genotype coverage, superior resistance profile, and high levels of active triphosphate in vivo in the liver compared to our first and second generation nucleoside inhibitors of this class. Consequently, PSI-352938 was selected for further development and an efficient and scalable synthesis was sought to support clinical development. We report an improved, diastereoselective synthesis of a key 1'-β-nucleoside intermediate 13 via S(N)2 displacement of 1-α-bromo ribofuranose sugar 16 with the potassium salt of 6-chloro-2-amino purine and an efficient method to prepare cis-Rp cyclic phosphate (PSI-352938) in a highly stereoselective manner without any chromatographic purification. The 1-α-bromo sugar 16 was stereospecifically prepared from the corresponding 1-β-lactol in high yield under mild bromination conditions using CBr(4)/PPh(3) (Appel reaction). The desired cis-Rp 3',5'-cyclic phosphate construction was accomplished using isopropyl phosphorodichloridate readily obtained from POCl(3) and isopropyl alcohol. The base combination of Et(3)N/NMI was identified as a key factor for producing PSI-352938 as the major (>95%) diastereomer (cis-Rp) in high yield after the final cyclization step. The current route described in this article was successfully used to produce PSI-352938 on multikilogram scale.

UI MeSH Term Description Entries
D009705 Nucleosides Purine or pyrimidine bases attached to a ribose or deoxyribose. (From King & Stansfield, A Dictionary of Genetics, 4th ed) Nucleoside,Nucleoside Analog,Nucleoside Analogs,Analog, Nucleoside,Analogs, Nucleoside
D011355 Prodrugs A compound that, on administration, must undergo chemical conversion by metabolic processes before becoming the pharmacologically active drug for which it is a prodrug. Drug Precursor,Drug Precursors,Pro-Drug,Prodrug,Pro-Drugs,Precursor, Drug,Precursors, Drug,Pro Drug,Pro Drugs
D003498 Cyclic P-Oxides Heterocyclic P-Oxides,Cyclic P Oxides,Heterocyclic P Oxides,Oxides, Cyclic P,P Oxides, Cyclic,P-Oxides, Cyclic,P-Oxides, Heterocyclic
D003500 Cyclization Changing an open-chain hydrocarbon to a closed ring. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed) Cyclizations
D000998 Antiviral Agents Agents used in the prophylaxis or therapy of VIRUS DISEASES. Some of the ways they may act include preventing viral replication by inhibiting viral DNA polymerase; binding to specific cell-surface receptors and inhibiting viral penetration or uncoating; inhibiting viral protein synthesis; or blocking late stages of virus assembly. Antiviral,Antiviral Agent,Antiviral Drug,Antivirals,Antiviral Drugs,Agent, Antiviral,Agents, Antiviral,Drug, Antiviral,Drugs, Antiviral
D013237 Stereoisomerism The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed) Molecular Stereochemistry,Stereoisomers,Stereochemistry, Molecular,Stereoisomer
D013379 Substrate Specificity A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts. Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D016174 Hepacivirus A genus of FLAVIVIRIDAE causing parenterally-transmitted HEPATITIS C which is associated with transfusions and drug abuse. Hepatitis C virus is the type species. Hepatitis C virus,Hepatitis C-Like Viruses,Hepaciviruses,Hepatitis C Like Viruses,Hepatitis C viruses,Hepatitis C-Like Virus

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