title: cycloSal-2',3'-dideoxy-2',3'-didehydrothymidine monophosphate (cycloSal-d4TMP): synthesis and antiviral evaluation of a new d4TMP delivery system.
abstract: The synthesis, hydrolysis, and antiviral evaluation of novel, lipophilic cycloSal-d4TMP derivatives 3a-h of the anti-HIV dideoxynucleoside 2',3'-dideoxy-2',3'-didehydrothymidine (d4T, 1) are reported. This pro-nucleotide concept has been designed to deliver d4TMP (2) by selective chemical hydrolysis. All compounds 3a-h were synthesized using phosphorus(III) chemistry in good yields and in somewhat lower yields using phosphorus(V) chemistry starting from substituted salicyl alcohols 6a-h. The phosphotriesters 3 were obtained without stereochemical preference with respect to the configuration at the phosphorus center as 1:1 diastereomeric mixtures. However, a few of the triesters 3 could be separated into the diastereomers by means of semipreparative HPLC. In a 1-octanol/phosphate buffer mixture, all compounds 3 exhibited 9-100-fold higher lipophilicity as judged from their Pa values as compared to d4T (1). Furthermore, in hydrolysis studies 3 decomposed under mild aqueous basic conditions releasing solely d4TMP (2) and the diols 6 following the designed tandem reaction sequence. A correlation of the electronic properties introduced by the substituents and the half-lives of triesters 3 was observed. Thus, by varying the substituent, the half-lives of 3 could be adjusted over a wide range of compounds still delivering d4TMP (2) selectively. Phosphotriesters 3 exhibited considerable activity against HIV-1 and HIV-2 in wild-type human T-lymphocyte (CEM/O) cells as well as mutant thymidine kinase-deficient (CEM/TK-) cells. Surprisingly, we observed a 3-80-fold difference in antiviral activity between the two diastereomers. Our data clearly prove that the cycloSal-d4TMPs deliver exclusively the nucleotide d4TMP not only under simulated hydrolysis conditions but also under cellular conditions and thus fulfill the thymidine kinase-bypass premise. Therefore, the cycloSal-nucleotide concept is the first reported pro-nucleotide system that delivers the dideoxynucleotide by a pH-driven, chemically activated, tandem reaction without the requirement of an enzymatic contribution.
authors.affiliation: Institute of Organic Chemistry, Julius-Maximilians-University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Meier
authors.forename: M
authors.initials: M
authors.lastname: Lorey
authors.forename: E
authors.initials: E
authors.lastname: De Clercq
authors.forename: J
authors.initials: J
authors.lastname: Balzarini
mesh_terms: D000818:Animals; D019380:Anti-HIV Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D002021:Buffers; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D016503:Drug Delivery Systems; D015497:HIV-1 / Q000187:drug effects; D015498:HIV-2 / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D009154:Mutation; D000442:Octanols; D010755:Organophosphates / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D011355:Prodrugs / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D012995:Solubility; D018119:Stavudine / Q000737:chemistry* / Q000493:pharmacokinetics; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000821:virology; D013937:Thymidine Kinase / Q000172:deficiency; D013938:Thymidine Monophosphate / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics; D014407:Tumor Cells, Cultured
chemical_list: D019380:Anti-HIV Agents; D002021:Buffers; D000442:Octanols; D010755:Organophosphates; D011355:Prodrugs; D013938:Thymidine Monophosphate; D018119:Stavudine; D013937:Thymidine Kinase