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.
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。
Cyclosporin Analogs Modified in the 3,7,8-Positions: Substituent Effects on Peptidylprolyl Isomerase Inhibition and Immunosuppressive Activity Are Nonadditive
作者:Ming-Kuan Hu、Alison Badger、Daniel H. Rich
DOI:10.1021/jm00021a005
日期:1995.10
Four analogs of cyclosporin A (CsA) were synthesized to determine if the biological activities of CsAanalogs generated by multiple amino acid replacements are predictable from the effects on biological activity of analogs with single residue changes. CsAanalogs [Phe7]CsA (8a), [D-MeAla3,Phe7]CsA (8b), [D-Ser8,Phe7]CsA (8c), and [D-MeAla3,Phe7,D-Ser8]CsA (8d) were designed by modification of positions
Synthesis, conformation and immunosuppressive activity of a conformationally restricted cyclosporin lactam analog
作者:Johannes D. Aebi、Dominique Guillaume、Brian E. Dunlap、Daniel H. Rich
DOI:10.1021/jm00117a022
日期:1988.9
Cyclosporine A (CsA, 1), an immunosuppressive cyclic undecapeptide, in apolar solvents adopts a II' beta-turn at the Sar3-MeLeu4 residues. [D-Proline3]Cs has been reported to be a nonimmunosuppressive analogue in which the II' beta-turn is retained. In order to determine if this loss of activity is caused by steric hindrance between the Cs analogue and its receptor or is caused by a change in the peptide conformation, an analogue that stabilizes a II' beta-turn has been synthesized, [lactam3,4]Cs. We also have studied the solution conformation of two other analogues, [D-MeAla3]Cs and [L-MeAla3]Cs. The conformations have been established by 1D difference NOE and 2D (NOESY or ROESY) NMR. The conformations of [lactam3,4]Cs and [D-MeAla3]Cs are indistinguishable from that of CsA in solution. [L-MeAla3]Cs was found to adopt a conformation with a cis amide bond between Sar3 and MeLeu4. The inhibition of concanavalin A stimulated thymocytes by CsA, [D-MeAla3]Cs, [L-MeAla3]Cs, and [lactam3,4]Cs gave IC50 values (nM) of 5, 6, 100, and 100, respectively. The weak immunosuppressive activity of [lactam3,4]Cs possessing the II' beta-turn suggests that the loss of activity for 4 is due to steric hindrance with the Cs receptor.
LEE, JIHAE PARK;DUNLAP, BRIAN;RICH, DANIEL H., INT. J. PEPTIDE AND PROTEIN PES., 35,(1990) N, C. 481-494
作者:LEE, JIHAE PARK、DUNLAP, BRIAN、RICH, DANIEL H.
DOI:——
日期:——
AEBI, JOHANNES D.;GUILLAUME, DOMINIQUE;DUNLAP, BRIAN E.;RICH, DANIEL H., J. MED. CHEM., 31,(1988) N 9, C. 1805-1815
作者:AEBI, JOHANNES D.、GUILLAUME, DOMINIQUE、DUNLAP, BRIAN E.、RICH, DANIEL H.