title: First isolation of disubstituted cis-5,6-dihydro-1,10-phenanthrolines. Lipase-mediated resolution of cis- and trans-phenoxy alcohol isomers and assignment of absolute stereochemistry via CD and NMR spectroscopy.
abstract: 5,6-Dihydro-1,10-phenanthrolines can display axial and central chirality. In conjunction with the ligating properties of the diimino moiety, this class of compounds is of great interest to applications in supramolecular chemistry. We report the first preparation of cis-5,6-dihydro-1,10-phenanthroline derivatives by reacting triphenyl borate with the corresponding epoxide precursor. We found that solvent and temperature choice determined the stereoselectivity of the epoxide opening giving rise to the cis (14:1 dr) or trans (99:1 dr) product. Racemates of each stereoisomeric mixture, cis- and trans-phenoxy alcohol, were separated via highly enantioselective transesterifications with lipase PSCI from Burkholderia cepacia (97% ee, E > 200). Stereochemical assignments were carried out using CD and X-ray analyses in conjunction with NMR studies of α-methoxy-α-(trifluoromethyl)phenylacetic acid and α-methoxyphenylacetic acid esters.
authors.affiliation: Department of Chemistry, Western Michigan University, Kalamazoo, Michigan 49008-5413, USA.
authors.forename: Lars
authors.initials: L
authors.lastname: Kohler
authors.forename: Elke
authors.initials: E
authors.lastname: Schoffers
authors.forename: Erin
authors.initials: E
authors.lastname: Driscoll
authors.forename: Matthias
authors.initials: M
authors.lastname: Zeller
authors.forename: Carla
authors.initials: C
authors.lastname: Schmiesing
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D055162:Biocatalysis; D016956:Burkholderia cepacia / Q000201:enzymology; D005591:Chemical Fractionation / Q000379:methods*; D002942:Circular Dichroism; D004951:Esterification; D008049:Lipase / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D010618:Phenanthrolines / Q000737:chemistry* / Q000302:isolation & purification*; D011551:Pseudomonas fluorescens / Q000201:enzymology; D013237:Stereoisomerism; D013997:Time Factors
chemical_list: D000438:Alcohols; D010618:Phenanthrolines; D008049:Lipase; C025205:1,10-phenanthroline