A Strategy for the Asymmetric Aminohomologation of α,β-Dihydroxy Aldehydes: Application to the Synthesis of the Southwest Tripeptide Segment of Echinocandin B
摘要:
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 cyclo-expansion 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((OSiBuPh2)-Bu-t)OMe and further acylation with the N-Cbz protected L-4-tert-butyldiphenylsilyloxy proline rendered the southwest portion of echinocandin B.
A Strategy for the Asymmetric Aminohomologation of α,β-Dihydroxy Aldehydes: Application to the Synthesis of the Southwest Tripeptide Segment of Echinocandin B
摘要:
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 cyclo-expansion 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((OSiBuPh2)-Bu-t)OMe and further acylation with the N-Cbz protected L-4-tert-butyldiphenylsilyloxy proline rendered the southwest portion of echinocandin B.
Iodonitrene in Action: Direct Transformation of Amino Acids into Terminal Diazirines and <sup>15</sup>N<sub>2</sub>-Diazirines and Their Application as Hyperpolarized Markers
作者:Thomas Glachet、Hamid Marzag、Nathalie Saraiva Rosa、Johannes F. P. Colell、Guannan Zhang、Warren S. Warren、Xavier Franck、Thomas Theis、Vincent Reboul
DOI:10.1021/jacs.9b07035
日期:2019.8.28
terminal diazirines has been developed using phenyliodonium diacetate (PIDA) and ammonia. This PIDA mediated transformation occurs via three consecutive reactions and involves an iodonitrene intermediate. This method is tolerant to most functional groups found on the lateral chain of amino acids, it is operationally simple, and can be scaled up to provide multigram quantities of diazirine. Interestingly
A Strategy for the Asymmetric Aminohomologation of α,β-Dihydroxy Aldehydes: Application to the Synthesis of the Southwest Tripeptide Segment of Echinocandin B
作者:Claudio Palomo、Mikel Oiarbide、Aitor Landa
DOI:10.1021/jo990964c
日期:2000.1.1
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 cyclo-expansion 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((OSiBuPh2)-Bu-t)OMe and further acylation with the N-Cbz protected L-4-tert-butyldiphenylsilyloxy proline rendered the southwest portion of echinocandin B.