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. Author manuscript; available in PMC: 2019 Apr 20.
Published in final edited form as: J Org Chem. 2018 Apr 5;83(8):4491–4504. doi: 10.1021/acs.joc.8b00207

Figure 5.

Figure 5

(A) 1H–1H NOESY NMR of P25 revealed 14 inter-residue NOE correlations. Red: evidence of NHval–C=OThr γ-turn NHval–C=OPG β-turn. Magenta: flexibility of NHval to rotate beneath Pro. Orange: relating to ψ–angle of pThr. Blue: relating to side-chain dihedral angle of pThr. Green: correlation between phosphoric acid and NHThr, (B) Proposed structure of P25, resulting from an equilbirum between a γ-turn and β-turn. (C–D) Mechanistic models for formation of cis- and trans- products, which incorporate the above hybrid γ/β-turn. Putative H-bonding interactions are shown in magenta.