Semi-synthesis of Polymyxin B (2-10) and Colistin (2-10) Analogs Employing the Trichloroethoxycarbonyl (Troc) Group for Side Chain Protection of .ALPHA.,.GAMMA.-Diaminobutyric Acid Residues
作者:Keiko Okimura、Kazuhiro Ohki、Yuki Sato、Kuniharu Ohnishi、Naoki Sakura
DOI:10.1248/cpb.55.1724
日期:——
Improved strategies for the chemical conversion of natural polymyxin B and colistin to their N-terminal analogs are reported. First, the protection of the side chains of five L-α,γ-diaminobutyric acid (Dab) residues in natural polymyxin B and colistin was achieved with trichloroethoxycarbonyl (Troc), then the resulting pentakis(Nγ-Troc)-polymyxin B and pentakis(Nγ-Troc)-colistin were treated with trifluoroacetic acid (TFA) : methanesulfonic acid (MSA) : dimethylformamide (DMF) : H2O (10 : 30 : 55 : 5) at 40 °C in order to remove Nα-alkanoyl-Dab(Troc)-OH selectively. The new key compounds, tetrakis(Nγ-Troc)-polymyxin B (2-10) and tetrakis(Nγ-Troc)-colistin (2-10), were obtained in 19% and 15% yields, respectively, which is higher than previous reports using trifluoroacetyl (Tfa) for tetrakis(Nγ-Tfa)-polymyxin B (2-10) and tetrakis(Nγ-Tfa)-colistin (2-10), respectively. Acylation of tetrakis(Nγ-Troc)-polymyxin B (2-10) and tetrakis(Nγ-Troc)-colistin (2-10) with various hydrophobic acids bearing aliphatic or aromatic ring structures, followed by the deprotection of Troc by Zn in AcOH, produced polymyxin B (2-10) and colistin (2-10) analogs which were used for structure–activity relationship studies. It was found that cyclohexylbutanoyl-, 4-biphenylacetyl-, and 1-adamantaneacetyl-polymyxin B (2-10) showed potent antimicrobial activity equal to that of polymyxin B against three Gram-negative bacterial strains. The lipopolysacharide (LPS) binding activity of cyclohexylbutanoyl-, 4-biphenylacetyl-, and cyclododecanecarbonyl-polymyxin B (2-10) increased greatly in comparison with that of polymyxin B (2-10). The various Nα-acylated polymyxin B (2-10) analogs showed slightly higher antimicrobial and LPS binding activities than the corresponding Nα-acylated colistin (2-10) analogs.
报告了将天然多粘菌素 B 和秋水仙素化学转化为其 N 端类似物的改进策略。首先,用三氯乙氧羰基(Troc)保护天然多粘菌素 B 和秋水仙素中五个 <小>L小>-α,γ-二氨基丁酸(Dab)残基的侧链,然后用三氟乙酸(TFA):甲磺酸(MSA): 二甲基甲酰胺(DMF):H2O (10 : 30 : 55 : 5) 在 40 °C 下处理,以选择性地去除 Nα-alkanoyl-Dab(Troc)-OH 。新的关键化合物四(Nγ-Troc)-多粘菌素 B (2-10)和四(Nγ-Troc)-colistin (2-10)的收率分别为 19% 和 15%,高于之前使用三氟乙酰(Tfa)分别制备四(Nγ-Tfa)-多粘菌素 B (2-10) 和四(Nγ-Tfa)-colistin (2-10)的报道。四(Nγ-Troc)-多粘菌素 B (2-10)和四(Nγ-Troc)-考利司汀(2-10)与各种具有脂肪环或芳香环结构的疏水酸进行酰化,然后在 AcOH 中用 Zn 对 Troc 进行脱保护,得到多粘菌素 B (2-10) 和考利司汀 (2-10) 类似物,并将其用于结构-活性关系研究。研究发现,环己基丁酰基、4-联苯乙酰基和 1-金刚烷乙酰基多粘菌素 B (2-10) 对三种革兰氏阴性细菌菌株的抗菌活性与多粘菌素 B 相当。与多粘菌素 B(2-10)相比,环己基丁酰基、4-联苯乙酰基和环十二羰基多粘菌素 B(2-10)的脂多糖羧酸(LPS)结合活性大大提高。各种 Nα-acylated polymyxin B (2-10) 类似物的抗菌活性和 LPS 结合活性略高于相应的 Nα-acylated colistin (2-10) 类似物。