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J Org Chem. 2000 Jan 14;65(1):41-6.

A strategy for the asymmetric aminohomologation of alpha, beta-dihydroxy aldehydes: application to the synthesis of the southwest tripeptide segment of echinocandin B.

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  • 1Departamento de Química Orgánica. Facultad de Química. Universidad del País Vasco, Apdo 1072, 20080 San Sebastián, Spain.

Abstract

The synthesis of the (2S,3S,4S)-3,4-dihydroxyhomotyrosine amino acid segment, present in echinocandin B, in its activated form ready for peptide coupling is described. The key steps of the approach are the enantioselective AD reaction of 4-methoxycinnamic acid methyl ester, a completely diastereoselective [2 + 2] hydroxyketene-imine cycloaddition, and the TEMPO-assisted cycloexpansion of the resulting 3-hydroxy beta-lactam to the corresponding alpha-amino acid N-carboxy anhydride (NCA). The smooth opening of the latter upon treatment with L-Thr(OSi(t)BuPh(2))OMe and further acylation with the N-Cbz protected L-4-tert-butyldiphenylsilyloxy proline rendered the southwest portion of echinocandin B.

PMID:
10813893
[PubMed - indexed for MEDLINE]
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