Liu Chao, Dobhal Mahabeer P, Ethirajan Manivannan, Missert Joseph R, Pandey Ravindra K, Balasubramanian Sathyamangalam, Sukumaran Dinesh K, Zhang Min, Kadish Karl M, Ohkubo Kei, Fukuzumi Shunichi
Chemistry Division, PDT Center, Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
J Am Chem Soc. 2008 Oct 29;130(43):14311-23. doi: 10.1021/ja8050298. Epub 2008 Oct 2.
The oxidation of bacteriopyropheophorbide with ferric chloride hexahydrate or its anhydrous form produced the ring-D oxidized (ring-B reduced) chlorin in >95% yield. Replacing the five-member isocyclic ring in bacteriopyropheophorbide- a with a fused six-member N-butylimide ring system made no difference in regioselective oxidation, and the corresponding ring-B reduced chlorin was isolated in almost quantitative yield. When the oxidant was replaced by 2,3-dichloro-5,6-dicyano-p-benzoquinone, which is frequently used at the oxidizing stage of the porphyrin synthesis, the ring-B oxidized (ring-D reduced) chlorins were obtained. With both ring-B reduced and ring-D reduced chlorins in hand, their photophysical and electrochemical properties were examined and compared for the first time. The ring-B reduced chlorine 20, with a fused six-member N-butylimide ring, exhibits the most red-shifted absorption band (at lambda(max) = 746 nm), the lowest fluorescence quantum yield (4.5%), and the largest quantum yield of singlet oxygen formation (67%) among the reduced ring-B and ring-D chlorins investigated in this study. Measurements of the one-electron oxidation and reduction potentials show that compound 20 is also the easiest to oxidize among the examined compounds and the third easiest to reduce. In addition, the 1.62 eV HOMO-LUMO gap of 20 is the smallest of the examined compounds, and this agrees with values calculated using the DFT method. Spectroelectrochemical measurements afforded UV-visible absorption spectra for both the radical cations and radical anions of the examined chlorins. The ring-B reduced compound 20, with a fused six-member N-butylimide ring, is regarded as the most promising candidate in this study for photodynamic therapy because it has the longest wavelength absorption and the largest quantum yield of singlet oxygen formation among the compounds investigated.
用六水合氯化铁或其无水形式氧化细菌焦脱镁叶绿酸，生成的D环氧化（B环还原）二氢卟吩产率>95%。用稠合的六元N-丁基酰亚胺环体系取代细菌焦脱镁叶绿酸-a中的五元异环，区域选择性氧化没有差异，相应的B环还原二氢卟吩以几乎定量的产率分离得到。当氧化剂被卟啉合成氧化阶段常用的2,3-二氯-5,6-二氰基对苯醌取代时，得到了B环氧化（D环还原）二氢卟吩。有了B环还原和D环还原二氢卟吩后，首次对它们的光物理和电化学性质进行了研究和比较。带有稠合六元N-丁基酰亚胺环的B环还原二氢卟吩20，在本研究中所研究的B环还原和D环还原二氢卟吩中，呈现出最大红移的吸收带（λmax = 746 nm）、最低的荧光量子产率（4.5%）和最大的单线态氧形成量子产率（67%）。单电子氧化和还原电位的测量表明，化合物20在被检测的化合物中也是最容易氧化的，并且是第三容易还原的。此外，20的1.62 eV的HOMO-LUMO能隙是被检测化合物中最小的，这与使用DFT方法计算的值一致。光谱电化学测量给出了被检测二氢卟吩的自由基阳离子和自由基阴离子的紫外可见吸收光谱。带有稠合六元N-丁基酰亚胺环的B环还原化合物20，被认为是本研究中光动力疗法最有前景的候选物，因为在所研究的化合物中它具有最长波长的吸收和最大的单线态氧形成量子产率。
