(2S,4R)-4-hydroxyproline(4-nitrobenzoate): strong induction of stereoelectronic effects via a readily synthesized proline derivative. Crystallographic observation of a correlation between torsion angle and bond length in a hyperconjugative interaction.
(2S,4R)-4-Hydroxyproline(4-nitrobenzoate) was synthesized. The crystal structure revealed an exo ring pucker, with the nitrobenzoate pseudoaxial on the pyrrolidine envelope and antiperiplanar to C(β) and C(δ) C-H bonds. The unit cell exhibited variation in C(δ)-H/C(γ)-O and C(β)-H/C(γ)-O torsion angles, with a 15° increase in torsion angle (148° to 163°) observed to result in a 0.018 Å decrease in C(δ)-H/C(γ)-O bond length, consistent with favorable σC-H → σ*C-O hyperconjugative interactions increasing with greater orbital overlap.
Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States.
Anil K
AK
Pandey
Glenn P A
GP
Yap
Neal J
NJ
Zondlo
D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D011392:Proline / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry
C000593150:(2S,4R)-4-hydroxyproline(4-nitrobenzoate); D011392:Proline