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[Ala8]-dynorphin A, a potent «-selective opioid heptadecapeptide with numerous sensitive side-chain residues, has been prepared by solid-phase synthesis using base-labile JVa-9-fluorenylmethyloxycarbonyl (Fmoc) protection and side-chain anchoring to a tris (alkoxy) benzylamide “PAL”-resin. Final cleavage anddeprotection was carried out with reagent R, trifluoroacetic acid-thioanisole-l, 2-ethanedithiol-anisole (90: 5: 3: 2), reagent K, trifluoroacetic acid-phenol-water-thioanisole-l, 2-ethanedithiol (82.5: 5: 5: 5: 2.5), and reagentB, trifluoroacetic acid-phenol-water-triisopropylsilane (88: 5: 5: 2); optimal reaction and workup conditions are described. Crude peptide products were evaluated by analytical high-performance liquid chromatography (HPLC), capillary zone electrophoresis (CZE), ánd direct fast atom bombardment and ion electrospray mass spectrometry (FABMS and ESMS). Tryptophan alkylation side …