Computational Study on the Conformational Flexibility-Mediated Intramolecular Oxidative Spirocyclization of Procyanidin B4

• DOI: 10.1021/acs.joc.4c01183
• Publication Date: 2024-08-09T19:13:47Z
• Authors: Haruka Kataoka; Yuya Kakumu; Davidson Obinna Agbo; Tohru Taniguchi; Emiko Yanase

Procyanidins, found widely in foods and beverages, are prone to oxidation, yet the chemical structures of their oxidation products mechanisms involved remain unclear. Herein, we report that conformation procyanidin B4 influences its stereochemistry. Eight spirocyclized were obtained from classified as S- or R-forms based on configuration spiro carbons. The ratios derived compact extended rotamers B4, respectively, varied with solvent. DFT calculations suggested four lowest-energy conformers diverged by interflavan bond rotation heterocyclic ring inversion. Conformations an axial-oriented B-ring estimated reactive conformations showing proximity between reaction sites B- D-rings. Moreover, rotamer bearing axially oriented showed greater stabilization noncovalent interactions (NCIs), such OH−π interactions, compared counterpart rotamer. This NCI-based accounts for a higher production R-form despite predominant presence H2O. These findings highlight conformational effects bias stereoselectivity oxidative spirocyclization advancing our understanding product