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. Author manuscript; available in PMC: 2016 Nov 1.
Published in final edited form as: Org Lett. 2016 Jul 13;18(15):3614–3617. doi: 10.1021/acs.orglett.6b01655

Figure 2.

Figure 2

Keto/enol tautomerization and trans/cis isomerization of β-keto amides of substituted prolines. An nπ* interaction can occur in the trans isomer. Integration of the 1H NMR signal of the alkenyl proton (red) in the trans enol species reports on the effect of the nπ* interaction on the hydrogen bond.