Steric challenges in Staudinger reaction

Syntheses of oligomers of furanoid sugar amino acids (AFUs, X), particularly α/β pentapeptides H-GG-X-GG-OH incorporating RibAFU(ip) (tX) or XylAFU(ip) (cX), were accomplished. The precursors for syntheses were azido compounds, N3-tX-OH and N3-cX-OH or Fmoc-tX-OH, using pathways starting from D-glucose. The oligomers can be synthesized on solid phase using N3-X-OH, investigating with the Ph3P or the more reactive nBu3P reagent via the Staudinger reaction, as well as by Fmoc-X-OH, with different conditions.

Use of Ph3P as Staudinger reagent is “ineffective” in the case of a cis stereoisomer, if cX is attached to the preceding residue with a peptide (–CONH–) bond. It was explained by X-Ray diffraction, NMR spectroscopic measurements, theoretical (QM) data with conformation search and subsequent DFT calculations.

Stau Ap

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