反应详情

Amino acids were purchased from Advanced Chemtech (Louisville, Ky.), and used as the following derivatives: N-Fmoc-D-Ala-OH.H2O, N-Fmoc-D-Leu-OH, N-Fmoc-D-Glu(O-t-Bu)-OH, N-Fmoc-D-Pro-OH, N-Fmoc-D-Tyr(O-t-Bu), N-Fmoc-D-Arg(Pmc)-OH. (R)-β-hydroxy-N-(Fmoc)valine was prepared from (R)-β-hydroxy-N-(Boc)valine (Dettwiler et al., 2003) by removal of the Boc group (1:1 TFA (trifluoroacetic acid)/CH2Cl2), protection with Fmoc-OSu and NaHCO3 in aqueous acetone (Capatsanis et al. 1983), followed by purification by chromatography over silica gel (1:1:98 MeOH/HOAc/CHCl3) and lyophilization from aqueous acetonitrile (78% yield). (3R,6R,9R)-2-Oxo-3-[N-(Fmoc)amino]-1-azabicyclo[4.3.0]-nonane-9-carboxylic acid was prepared from (3R,6R,9R)-methyl 2-oxo-3-amino-1-azabicyclo[4.3.0]-nonane-9-carboxylate (in turn prepared (Lombart et al. 1996) from D-glutamic acid) by Fmoc-protection with Fmoc-OSu and NaHCO3 in aqueous acetone (Capatsanis et al. 1983), followed by selective hydrolysis of the methyl ester (Pascal et al. 1998). Peptide synthesis was performed on a 0.1 mmol scale (200 mg resin), and conducted by deprotection with piperidine in DMF (10 ml/g resin, 20% v/v, 1×2 min, 1×3 min, 1×10 min) followed by washing with DMF (10 ml/g resin, 5×1 min). Fmoc protected amino acid (0.5 mmol, 500 mol %) dissolved in a solution of TBTU in DMF (0.25 M, 2 ml) was added to the resin. After agitation of the resin (5 min), DIEA (0.6 mmol, 600 mol %) was added, and agitation continued for 1 h. The resin was washed with DMF (10 ml/g resin, 5×1 min), and coupling efficiency determined using the Kaiser test. The resin was agitated using a mechanical vortex apparatus during coupling, rinsing and deprotection sequences. Rp-HPLC analysis was performed on an Alltech C18 column (dimensions 250 mm×4.6 mm) using acetonitrile/water/TFA mixtures, where solvent A=water/0.1% TFA and solvent B=MeCN/0.1% TFA (see below). The flow rate was 0.5 ml/min, and detection was performed at 214 nM.

1. washby washing with DMF (10 ml/g resin, 5×1 min)
2. additionwas added to the resin
3. washThe resin was washed with DMF (10 ml/g resin, 5×1 min)
4. washrinsing