Wang L, Morin K W, Kumar R, Cheraghali M, Todd K G, Baker G B, Knaus E E, Wiebe L I
University of Alberta, Edmonton, Canada.
J Med Chem. 1996 Feb 16;39(4):826-33. doi: 10.1021/jm9408326.
A new class of 5-halo-6-alkoxy-5,6-dihydro-3'-azido-3'-deoxythymidine diastereomers (5-x-6-OR -5,6-dihydro-AZTs; X = I, Br, Cl; R = Me, Et) were evaluated as potential anti-AIDS prodrugs of 3'-azido-3'-deoxythimidine (AZT). In vivo regeneration of AZT from these 5-X-6-OR-5,6-dihydro-AZTs was examined in Balb/c mice after intravenous tail vein injection. The (5R,6R)- and (5S,6S)-5-bromo(or iodo)-6-methoxy-5,6-dihydro derivatives of AZT (BMAZT, IMAZT) were rapidly converted to AZT, resulting in AZT plasma concentrations after a 144 micromol/kg dose similar to those after an equivalent dose (144 microg/kg, 38.5 mg/kg) of AZT, whereas AZT was not detectable by HPLC after the same dose of the chloro diastereomer (5R,6R)-CMAZT. The interaction of AZT and the 5-X-6-methoxy-5,6dihydro-AZT diastereomers with the 6-[(4-nitrobenzyl)thio]-9-beta-D-ribofuranosylpurine equilibrative-sensitive nucleoside transporter in murine erythrocytes was also studied. The (5R,6R)- and (5S,6S)-5-X-6-OMe-5,6-dihydro-AZT diastereomers demonstrated a high affinity (K(i) = 0.2-0.5 mM) for the transporter relative to AZT (K(i) = 1.3 mM), with the exception of (5S,6R)-5-chloro-6-methoxy-5,6-dihydro-3'-azido-3'-deoxythymidine (CMAZT) which has a K(i) value larger than 1.5 mM. [2-(14)C]-Labeled (5R,6R)- and (5S,6S)-5-bromo-6-methoxy(or ethoxy)- 5,6-dihydro-3'-azido-3'-deoxythymidines were synthesized by the regiospecific addition of methyl hypobromite or ethyl hypobromite to the 5,6-olefinic bond of [2-(14)C]-AZT in high radiochemical yield [(5R,6R)-BMAZT, 48%, and (5S,6S)-BMAZT, 33%; (5R,6R)-BEAZT, 61%, and (5S,6S)-BEAZT, 15%), high radiochemical purity (>98%), and high specific activity (56mCi/mmol)]. The amounts of radioactivity in mouse brain after iv injection of [2-(14))C]-labeled (5R,6R)-BMAZT, (5S,6S)-BMAZT, or (5R,6R)-BEAZT were 2-4 fold higher that that for [2-(14)C]-AZT (P < 0.05). The radioactivity remaining in blood after dosing with these 5-bromo-6-alkoxy-5,6-dihydro-AZTs was up to 20-fold higher than after injection of [2-(14)C]-AZT at longer time intervals after injection. The amounts of radioactivity present in femoral bone following injection of [2(-14)C]-AZT, or these 5-bromo-6-alkoxy-5,6-dihydro-AZTs, were similar. Subcellular and regional distributions of [2-(14)C]-labeled AZT, (5R,6R)-BMAZT, or (5R,6R)-BEAZT in mouse brain after jugular vein injection did not show preferential concentration in any particular subcellular fraction nor a marked preferential regional localization for either AZT or these 5,6-dihydro prodrugs of AZT.
一类新型的5-卤代-6-烷氧基-5,6-二氢-3'-叠氮基-3'-脱氧胸苷非对映异构体（5-x-6-OR -5,6-二氢-AZT；X = I、Br、Cl；R = Me、Et）被评估为3'-叠氮基-3'-脱氧胸苷（AZT）潜在的抗艾滋病前药。在Balb/c小鼠经尾静脉注射后，研究了这些5-X-6-OR-5,6-二氢-AZT在体内向AZT的转化情况。AZT的(5R,6R)-和(5S,6S)-5-溴（或碘）-6-甲氧基-5,6-二氢衍生物（BMAZT、IMAZT）能迅速转化为AZT，在给予144 μmol/kg剂量后，其血浆中AZT浓度与给予等量（144 μg/kg，38.5 mg/kg）AZT后的浓度相似，而给予相同剂量的氯代非对映异构体(5R,6R)-CMAZT后，通过高效液相色谱法未检测到AZT。还研究了AZT和5-X-6-甲氧基-5,6-二氢-AZT非对映异构体与小鼠红细胞中6-[(4-硝基苄基)硫基]-9-β-D-呋喃核糖基嘌呤平衡敏感核苷转运体的相互作用。相对于AZT（K(i)=1.3 mM），(5R,6R)-和(5S,6S)-5-X-6-OMe-5,6-二氢-AZT非对映异构体对该转运体表现出高亲和力（K(i)=0.2 - 0.5 mM），但(5S,6R)-5-氯-6-甲氧基-5,6-二氢-3'-叠氮基-3'-脱氧胸苷（CMAZT）的K(i)值大于1.5 mM除外。通过次溴酸甲酯或次溴酸乙酯对[2-(14)C]-AZT的5,6-烯键进行区域特异性加成，以高放射化学产率[（5R,6R）-BMAZT，48%，和（5S,6S）-BMAZT，33%；（5R,6R）-BEAZT，61%，和（5S,6S）-BEAZT，15%]合成了[2-(14)C]-标记的(5R,6R)-和(5S,6S)-5-溴-6-甲氧基（或乙氧基）-5,6-二氢-3'-叠氮基-3'-脱氧胸苷，具有高放射化学纯度（>98%）和高比活度（56 mCi/mmol）。经静脉注射[2-(14)C]-标记的(5R,6R)-BMAZT、(5S,6S)-BMAZT或(5R,6R)-BEAZT后，小鼠脑中的放射性活度是[2-(14)C]-AZT的2 - 4倍（P<0.05）。在注射这些5-溴-6-烷氧基-5,6-二氢-AZT后较长时间间隔时，血液中残留的放射性活度比注射[2-(14)C]-AZT后高20倍。注射[2-(14)C]-AZT或这些5-溴-6-烷氧基-5,6-二氢-AZT后，股骨中的放射性活度相似。经颈静脉注射后，[2-(14)C]-标记的AZT、(5R,6R)-BMAZT或(5R,6R)-BEAZT在小鼠脑中的亚细胞和区域分布未显示在任何特定亚细胞组分中有优先富集，也未显示AZT或这些AZT的5,6-二氢前药有明显的优先区域定位。
