Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The short-cut analog of neuropeptide Y (NPY), NPY 1YESK-Ahx-25RHYINKITRQRY-NH2, was synthesized on the amide anchor 5-(4-aminomethyl-3,5-dimethoxyphenoxy)valeric acid (ADPV) attached to polystyrene/1% divinylbenzene by using the 9-fluorenylmethoxycarbonyl/tert-butyl (Fmoc/tBu) strategy. Side-chain-to-side-chain cyclization of residues Glu2 to Lys30 of this linear heptadecapeptide amide was carried out by using different activating reagents under high-dilution conditions of the free peptide. The use of diphenylphosphoryl azide (DPPA) with the addition of triethylamine gave the highest yield of cyclic peptide. Replacing the tertiary amine by dipotassium hydrogen phosphate as an insoluble inorganic base did not improve the cyclization. Complete cyclization was achieved within four hours by using 2-(1H-benzotriazol-1-yl) -1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU) in combination with 1-hydroxybenzotriazol (HOBt) as activating agent, but the separation from excess TBTU resulted in lower yields. Reactions were monitored by HPLC and kinetic investigations were made. The identity and purity of the final product were proven by various analytical methods including atmospheric pressure ionization mass spectrometry (API-MS). The receptor binding constant of the cyclic analog was found to be comparable to that of NPY.
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