Table 1.

Summarized molecular features of the methyl esters of N-acetylamino acids as model compounds.^a

entry	compound	COSMO volume (in water), Å3	surface electrostatic potential at C4	logP	preferred C4-pucker	amide bond
						Ktrans/cis (in water, 25 °C)	kcis-to-trans (in water, 37 °C), s−1	ktrans-to-cis (in water, 37 °C), s−1
Pro		214	positive	−0.44 ± 0.05	endo/exo mix	4.95 ± 0.05	0.033 ± 0.002	0.0070 ± 0.0005
R-Flp		222	positive and negative	−0.66 ± 0.03	exo	7.16 ± 0.31	0.087 ± 0.009	0.012 ± 0.002
S-Flp		221	negative and positive	−0.84 ± 0.05	endo	2.62 ± 0.07	0.041 ± 0.004	0.016 ± 0.002
Dfp		230	negative	−0.29 ± 0.04	endo/exo mix	3.49 ± 0.11	0.163 ± 0.016	0.049 ± 0.003

^aSee references [16,19,51–52,55] for details.