Hplc grade mecn

Unless otherwise specified, all commercially available reagents were used without further purification. Anhydrous Et₂O, PhMe, n-hexane, MeCN, DMF, DMSO, and CH₂Cl₂ were purchased from Fisher; THF was purchased from EMD, and PhH was purchased from Sigma-Aldrich. These were passed through a commercial solvent purification system (two columns of alumina) and used without further drying. HPLC grade MeCN and H₂O were purchased from Fisher. Triethylamine, diisopropylamine, pyridine, and Hünig’s base were distilled over CaH₂ immediately prior to use. All L-amino acids and HATU were purchased from Chem-Impex Int’l. Inc. unless otherwise noted. 4-Mercaptophenylacetic acid and 4-nitrophenyl chloroformate were purchased from Alfa Aesar. 4-Fluoro-3-nitrobenzoic acid and Tris(2-carboxyethyl)phosphine·HCl were purchased from Oakwood Chemical. Methylamine (33 wt %) in absolute ethanol, guanidine·HCl, H-Pro-OH, and H-Ala-OH were purchased from Sigma-Aldrich. Sodium thiophenylate was purchased from Santa Cruz Biotechnology. Ethyl 3-mercaptopropionate was purchased from TCI America. H-Gly-OH was purchased from J. T. Baker (Fisher).