Wiley-VCH Verlag, ChemInform, 20(35), 2004
Elsevier, Tetrahedron Letters, 6(45), p. 1237-1242
DOI: 10.1016/j.tetlet.2003.11.133
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A concise synthesis of novel homochiral aromatic amino acid surrogates comprising a tetrahydroindazole or a benzisoxazole system was developed via the acylation of a cyclic 1,3-diketone by the side-chain carboxyl functionality of either Boc-Asp-OtBu or Boc-Glu-OtBu followed by regioselective condensation with hydrazine, N-benzylhydrazine and hydroxylamine. The tetrahydroindazole nucleus was also constructed by the condensation of Boc-Asp-OtBu with the enamine, 1-pyrrolidino-1-cyclohexene followed by acid-hydrolytic treatment and reaction with hydrazines. Further functional group transformations gave Nα-Fmoc-protected derivatives as useful building blocks for solid-phase peptide assembly.