title: Comparative study of bis(benzyl)phosphate triesters of 2',3'-dideoxy-2',3'-didehydrothymidine (d4T) and cyclosal-d4TMP--hydrolysis, mechanistic insights and anti-HIV activity.
abstract: A comparative study of three cycloSal-d4TMP 1, 2 and 3 and a variety of bis(benzyl) phosphate triester 4-8 of the antivirally active nucleoside analogue 2',3'-dideoxy-2',3'-didehydrothymidine (d4T) will be described. This study has been initiated by the observation that the introduction of a simple 7-methyl group in the cycloSal-structure (2) led to a completely different hydrolysis pattern as compared to the prototype cycloSal-d4TMP 1. Instead of the selective formation of d4TMP, a phenyl phosphate diester was formed in the case of the 7-methyl-substituted compound 2. The difference in degradation pathway was caused by a change of the reaction mechanism. The phenyl phosphate diester was chemically and enzymatically inert to further cleavage to yield d4TMP. For comparison bis(benzyl)-d4TMP 4, bis(alpha-methylbenzyl)-d4TMP 5, bis(alpha-methoxycarbonylmethyl [MCM]-benzyl)-d4TMP 6 as well as the enzyme-cleavable bis(4-acetoxybenzyl)-d4TMP [bis(AB)-d4TMP(7 and bis(alpha-methoxycarbonylmethyl-4-acetoxybenzyl)-d4TMP [bis(alpha-MCM-AB)-d4TMP] 8 were synthesized. Chemical hydrolysis studies proved that all bis(benzyl) triesters hydrolyze to give the intermediate benzyl phosphate diesters. Moreover, the latter two triesters 7,8 and cycloSal-d4TMPs 1 and 3 led finally to the delivery of d4TMP. The chemical hydrolysis studies allowed a detailed mechanistic interpretation of the degradation pathways of triesters 1-8. Cell extract studies of the bis(benzyl) triesters 4-8 confirmed that only triesters 7 and 8 released d4TMP although with a considerable increase of the reaction rate. Anti-HIV evaluation of the compounds showed that cycloSal-d4TMP 1 and the bis(AB) triesters 7,8 were entirely independent of the presence of cellular thymidine kinase (TK).
authors.affiliation: Institut für Organische Chemie, Universität Hamburg, Germany. chris.meier@chemie.uni-hamburg.de
authors.forename: Chris
authors.initials: C
authors.lastname: Meier
authors.forename: Ulrike
authors.initials: U
authors.lastname: Muus
authors.forename: Jürgen
authors.initials: J
authors.lastname: Renze
authors.forename: Lieve
authors.initials: L
authors.lastname: Naesens
authors.forename: Erik
authors.initials: E
authors.lastname: De Clercq
authors.forename: Jan
authors.initials: J
authors.lastname: Balzarini
mesh_terms: D019380:Anti-HIV Agents / Q000737:chemistry* / Q000378:metabolism; D054306:Dideoxynucleotides; D004952:Esters / Q000737:chemistry / Q000378:metabolism; D015497:HIV-1 / Q000187:drug effects; D015498:HIV-2 / Q000187:drug effects; D006801:Humans; D006868:Hydrolysis; D015394:Molecular Structure; D018119:Stavudine / Q000737:chemistry* / Q000378:metabolism / Q000031:analogs & derivatives; D013329:Structure-Activity Relationship; D013936:Thymidine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D013937:Thymidine Kinase; D013942:Thymine Nucleotides; D014407:Tumor Cells, Cultured
chemical_list: D019380:Anti-HIV Agents; C415254:Cyclosaligenyl-2',3'-didehydro-2',3'-dideoxythymidine monophosphate; D054306:Dideoxynucleotides; D004952:Esters; D013942:Thymine Nucleotides; D018119:Stavudine; D013937:Thymidine Kinase; D013936:Thymidine