The diastereomeric thiophosphoramidate analogs [(RP)- and (SP)-3â²,5â²-Tnp(s)T]
2 and the phosphoramidate analog [3â²,5â²-TnpT]
3 of thymidylyl-3â²,5â²-thymidine were prepared and their hydrolytic reactions over the pH-range 1â8 at 363.2 K were followed by RP HPLC. At pH < 6, an acid-catalyzed PâN3â² bond cleavage (first-order in [H+]) takes place with both 3â²,5â²-Tnp(s)T and 3â²,5â²-TnpT, the former being about 12 fold more stable than the latter. At pH > 4, Tnp(s)T undergoes two competing pH-independent reactions, desulfurization (yielding TnpT) and depyrimidination (cleavage of the N-glycosidic bond) the rates of which are of the same order of magnitude. Also with 3â²,5â²-TnpT the pH-independent depyrimidination competes with PâN3â² cleavage at pH > 5.
硫代
磷酰胺
酯类似物[(RP)-和(
SP)-3′,5′-Tnp(s)T]2以及
磷酰胺
酯类似物[3′,5′-TnpT]3的
胸苷基-3′,5′-
胸苷被制备出来,并在363.2 K下通过反相高效
液相色谱法跟踪了它们在pH范围1至8的
水解反应。在pH < 6时,酸催化的P-N3′键断裂([H+]的一级反应)在3′,5′-Tnp(s)T和3′,5′-TnpT中都会发生,前者比后者稳定约12倍。在pH > 4时,Tnp(s)T会经历两种竞争性的pH无关反应,去
硫化(生成TnpT)和去
嘧啶化(N-糖苷键断裂),这两种反应的速率是同一数量级的。同样,3′,5′-TnpT在pH > 5时,pH无关的去
嘧啶化与P-N3′键断裂竞争。