Total Synthesis of Cyclosporin O Both in Solution and in the Solid Phase Using Novel Thiazolium-, Immonium-, and Pyridinium-Type Coupling Reagents: BEMT, BDMP, and BEP1
摘要:
Cyclosporin O (1), an extensively N-methylated immunosuppressive cyclic undecapeptide isolated from Tolypocladium inflatum Gams, was synthesized in 20-23% overall yield via 4 + 7 segment condensation and cyclization by the combined utilization of novel thiazolium- and immonium-type peptide coupling reagents 2-bromo-3-ethyl-4-methyl thiazolium tetrafluoroborate (BEMT) and 5-(1H-benzotriazol-1-yloxy)-3,4-dihydro-1-methyl 2H-pyrrolium hexachloroantimonate (BDMP) as well as compound 2-bromo-1-ethyl pyridinium tetrafluoroborate (BEP). BEMT and BEP, which have been proven to be very efficient for the coupling of peptide segments containing N-alkylated amino acid residues with respect to the fast reaction speed, low racemization, and high yields, were used to construct hindered amide bonds in CsO with the addition of HOAt, whereas the most efficient HOBt-derived immonium type reagent, BDMP, was used to perform the coupling of coded amino acids in CsO. Thus, the highly hindered protected 8-11 tetrapeptide 25 was successfully synthesized using BEMT in 65% yield, and the 1-7 heptapeptide 21 was obtained in 52-55% yield by the rationally combined utilization of BDMP, BEMT, and BEP. The synthesis of the linear undecapeptide 27 of CsO in the solid phase using BEMT and BEP was accomplished for the further evaluation of the effectiveness of these reagents.
Total Synthesis of Cyclosporin O Both in Solution and in the Solid Phase Using Novel Thiazolium-, Immonium-, and Pyridinium-Type Coupling Reagents: BEMT, BDMP, and BEP1
摘要:
Cyclosporin O (1), an extensively N-methylated immunosuppressive cyclic undecapeptide isolated from Tolypocladium inflatum Gams, was synthesized in 20-23% overall yield via 4 + 7 segment condensation and cyclization by the combined utilization of novel thiazolium- and immonium-type peptide coupling reagents 2-bromo-3-ethyl-4-methyl thiazolium tetrafluoroborate (BEMT) and 5-(1H-benzotriazol-1-yloxy)-3,4-dihydro-1-methyl 2H-pyrrolium hexachloroantimonate (BDMP) as well as compound 2-bromo-1-ethyl pyridinium tetrafluoroborate (BEP). BEMT and BEP, which have been proven to be very efficient for the coupling of peptide segments containing N-alkylated amino acid residues with respect to the fast reaction speed, low racemization, and high yields, were used to construct hindered amide bonds in CsO with the addition of HOAt, whereas the most efficient HOBt-derived immonium type reagent, BDMP, was used to perform the coupling of coded amino acids in CsO. Thus, the highly hindered protected 8-11 tetrapeptide 25 was successfully synthesized using BEMT in 65% yield, and the 1-7 heptapeptide 21 was obtained in 52-55% yield by the rationally combined utilization of BDMP, BEMT, and BEP. The synthesis of the linear undecapeptide 27 of CsO in the solid phase using BEMT and BEP was accomplished for the further evaluation of the effectiveness of these reagents.
An epimerization free and efficient total synthesis of immunosuppressant cyclosporin O (CsO) by step-by-step assembly of amino acids in solution phase is reported. The couplings were performed by employing Fmoc-amino acid chlorides and were mediated by zinc dust under neutral conditions. The yield and purity of the coupling of sterically hindered N-methylamino acids to N-methylamino acids at positions
据报道,通过在溶液相中逐步组装氨基酸,可实现无差向异构和高效的免疫抑制剂环孢菌素O(CsO)的全合成。通过使用Fmoc-氨基酸氯化物进行偶联,并在中性条件下由锌粉介导。的空间耦合的产率和纯度受阻Ñ甲基氨基酸以Ñ甲基氨基酸在位置8,9,10,和11通过在这些特定接合点重复三次耦合增强。分离出与CsO和最终CsO有关的所有10种中间肽,并通过IR,1 H NMR,质谱和HPLC技术对其进行了完全表征。
A novel thiazolium type peptide coupling reagent for hindered amino acids
作者:Peng Li、Jie Cheng Xu
DOI:10.1016/s0040-4039(99)01763-3
日期:1999.11
A highly efficient couplingreagent, 2-bromo-3-ethyl-4-methyl thiazolium tetrafluoroborate (BEMT), was designed, synthesized and successfully applied to the synthesis of oligopeptides containing N-alkyl or α-C-dialkyl aminoacids. Its efficiency was evaluated by HPLC and 1H NMR methods, and demonstrated by synthesis of a number of N-methyl-rich peptide segments with good yields and negligible racemization
设计,合成了高效偶联试剂2-溴-3-乙基-4-甲基噻唑四氟硼酸酯(BEMT),并将其成功地用于合成包含N-烷基或α- C-二烷基氨基酸的寡肽。通过HPLC和1 H NMR方法评价了其效率,并通过合成了许多具有良好产率和可忽略的外消旋作用的富含N-甲基的肽段。通过HPLC,1 H NMR和IR监测研究了偶联机理。有人提出不稳定的(酰氧基)噻唑盐和N-保护的氨基酸溴化物是主要的活性中间体,伴随着N的形成-乙基-4-甲基噻唑烷酮和少量的恶唑酮和N保护的氨基酸酸酐。