Table 5.
Overall functional group effects on cis-trans isomerism in Ac-TAXN-NH2 peptides. ΔΔG = ΔGtrans/cis(4R stereoisomer) − ΔGtrans/cis(4S stereoisomer), with negative ΔG consistent with the magnitude of stereoelectronic effects and positive indicating steric effects dominating over stereoelectronic effects. By definition, for Pro (4R = 4S = H), ΔΔG = 0.00.
| Ac-TAP(4-X)N-NH2 X = | ΔΔG(4R-4S) kcal mol-1 |
|---|---|
| F | -0.87 |
| OBzNO2 | -0.82 |
| OBzCF3 | -0.65 |
| OMs | -0.59 |
| OH | -0.56 |
| azido | -0.54 |
| ONs | -0.53 |
| OPO3H– | -0.45 |
| OTs | -0.39 |
| OPO3Et2 | -0.38 |