Chalier Florence, Hardy Micaël, Ouari Olivier, Rockenbauer Antal, Tordo Paul
Chimie Biologie et Radicaux Libres, Aix-Marseille Université, CNRS UMR 6517, Centre de Saint Jérôme, case 521, 13397 Marseille Cedex 20, France.
J Org Chem. 2007 Oct 12;72(21):7886-92. doi: 10.1021/jo071070s. Epub 2007 Sep 20.
A general synthetic route to prepare derivatives of the DEPMPO nitrone (5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide) functionalized at C-4 was established via the synthesis of 4-HMDEPMPO nitrone (5-diethoxyphosphoryl-4-hydroxymethyl-5-methyl-1-pyrroline-N-oxide) that was obtained from reduction of the nitro compound 1. (4R*,5S*)-4-HMDEPMPO was successfully separated from its minor diastereoisomer and could be used to generate various substituted analogues. Among them, 4-NHSDEPMPO, 5-diethoxyphosphoryl-4-succinimidyloxycarbonyloxymethyl-5-methyl-1-pyrroline-N-oxide, constitutes a NH2-reactive precursor for further conjugation to relevant moieties such as targeting groups, labels, or drugs. From 4-NHSDEPMPO, a biotinylated nitrone was synthesized offering new perspectives for targeted delivery applications. A short study of the trapping behaviors of the (4R*,5S*)-isomer of these 4-HMDEPMPO analogues proved that they are as good as DEPMPO for detecting superoxide. For each isomer, only one diastereoisomer adduct was obtained, resulting from the addition of superoxide on the less hindered face of the nitrone, that is, trans to the phosphoryl group and the C-4 substituent. From spectra simulation and experiments in various solvents, we proved that ESR patterns of each adduct corresponded to the superimposed signals of two sets of conformers in a sufficiently slow chemical exchange to induce a widening and a dissymmetry of some of the signal lines. This phenomenon was drastically reduced when compared with that observed for DEPMPO superoxide and attributed to a similar chemical exchange, and it did not hamper spectrum assignment. Determination of the decay rate of the superoxide adduct of (4R*,5S*)-4-HMDEPMPO proved that it has a 25% longer half-life time than the superoxide adduct of DEPMPO.
通过合成4-HMDEPMPO硝酮（5-二乙氧基磷酰基-4-羟甲基-5-甲基-1-吡咯啉-N-氧化物）建立了一种通用的合成路线，以制备在C-4位官能化的DEPMPO硝酮（5-二乙氧基磷酰基-5-甲基-1-吡咯啉-N-氧化物）衍生物，该4-HMDEPMPO硝酮由硝基化合物1还原得到。（4R*，5S*）-4-HMDEPMPO已成功与其次要非对映异构体分离，并可用于生成各种取代类似物。其中，4-NHSDEPMPO，即5-二乙氧基磷酰基-4-琥珀酰亚胺氧基羰基氧甲基-5-甲基-1-吡咯啉-N-氧化物，构成了一种可与相关部分（如靶向基团、标记物或药物）进一步偶联的NH2反应性前体。由4-NHSDEPMPO合成了一种生物素化硝酮，为靶向递送应用提供了新的前景。对这些4-HMDEPMPO类似物的（4R*，5S*）-异构体的捕获行为进行的简短研究证明，它们在检测超氧化物方面与DEPMPO一样出色。对于每种异构体，仅获得一种非对映异构体加合物，这是由于超氧化物在硝酮位阻较小的面上加成所致，即与磷酰基和C-4取代基呈反式。通过光谱模拟和在各种溶剂中的实验，我们证明了每种加合物的ESR图谱对应于两组构象体的叠加信号，其化学交换足够缓慢，从而导致一些信号线变宽和不对称。与DEPMPO超氧化物加合物相比，这种现象显著减少，归因于类似的化学交换，并且它不妨碍光谱归属。对（4R*，5S*）-4-HMDEPMPO超氧化物加合物的衰变率测定证明，其半衰期比DEPMPO超氧化物加合物长25%。
