87% |
With O-(1H-benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate; N-ethyl-N,N-diisopropylamine; In N,N-dimethyl-formamide; at 20.0℃; |
<strong>[53298-33-2]Fmoc-Cys(Bn)-OH</strong> (728 mg, 1.68 mmol), the trivalent ester 10 (350 mg, 842 lmol) and HBTU (637 mg, 1.68 mmol) were dried for 1 h in vacuo. Then dry DMF (20 mL) and DIPEA (577 mumol, 3.37 mmol) were added and it was stirred overnight at ambient temperature. Solvents were removed under reduced pressure and the crude product was dissolved in dichloromethane (25 mL). It was washed twice with water and brine (25 mL each), volatile compounds were removed under reduced pressure and the crude product was subjected to column chromatography (ethyl acetate/ cyclohexane, 1:4) yielding the title compound (609 mg, 733 mumol, 87%) as a colourless solid; Rf 0.34 (ethyl acetate/cyclohexane, 1:3); 1H NMR (500 MHz, CDCl3, 300 K) delta = 7.76 (d, 3J = 7.5 Hz, 2H, Hl), 7.62-7.59 (m, 2H, Haryl,Fmoc), 7.39 (mc, 2H, Haryl,Fmoc), 7.37-7.28 (m, 6H, Haryl,Fmoc, Haryl,benzyl), 7.26-7.22 (m, 1H, Haryl,benzyl), 6.32 (br s, 1H, NH), 5.61 (br s, 1H, NH), 4.44 (mc, 1H, CHHFmoc), 4.38 (br s, 1H, CHHFmoc), 4.23 (t, 3J = 7.1 Hz, 1H, CHFmoc), 4.12 (br s, 1H, HCys,a), 3.82-3.72 (m, 2H, CH2,benzyl), 2.88-2.80 (m, 1H, CH2,Cys, ba), 2.71 (mc, 1H, CH2,Cys, bb), 2.20 (mc, 6H, CCH2CH2C(O)), 1.95 (mc, 6H, CCH2CH2C(O)), 1.42 (s, 27H, C(CH3)3) ppm; 13C NMR (125 MHz, CDCl3, 300 K): delta = 172.7 (OC(O)), 169.0 (NHC(O)), 158.2 (OC(O)NH), 143.7 (Caryl,benzyl), 141.3, 141.3 (Caryl,Fmoc), 129.0, 128.7 (CHaryl,Fmoc), 127.7, 127.3, 127.1 (CHaryl,benzyl), 125.1, 120.0 (CHaryl,Fmoc), 80.7 (C(CH3)3), 67.2 (CH2,Fmoc), 58.0 (NHC(CH2CH2)3), 54.5 (CHCys,a), 47.5 (CHFmoc), 36.8 (CH2,benzyl), 34.2 (CH2,Cys,b), 29.9 (CCH2CH2C(O)), 29.7 (CCH2CH2C(O)), 28.1 (C(CH3)3)ppm; ESI MS: calcd for C47H62N2NaO9S: m/z 854.073 [M+Na]+; found: m/z 854.452 [M+Na]+. |