title: Absolute configurations of spiroiminodihydantoin and allantoin stereoisomers: comparison of computed and measured electronic circular dichroism spectra.
abstract: The assignment of absolute configurations is of critical importance for understanding the biochemical processing of DNA lesions. The diastereomeric spiroiminodihydantoin (Sp) lesions are oxidation products of guanine and 8-oxo-7,8-dihydroguanine (8-oxoG), and the absolute configurations of the two diastereomers, Sp1 and Sp2, have been evaluated by experimental and computational optical rotatory dispersion (ORD) methods. In order to support our previous assignments by the ORD method, we calculated the electronic circular dichroism spectra (ECD) of the Sp stereoisomers. Comparison of the experimentally measured and computed ECD spectra indicates that Sp1 has (-)-S absolute configuration, while Sp2 has (+)-R absolute configuration. Thus, the S and R assignments, based on the ECD spectra of Sp1 and Sp2, are consistent with our previous assignments of absolute configurations. To further test the validity of this approach, we performed a proof-of-principle computation of the ECD and ORD of the R and S enantiomers of allantoin (similar in chemical composition to Sp) of known absolute configurations. The calculations provide the correct assignment of the absolute configurations of the allantoin enantiomers, indicating that the computational TDDFT approach is robust for identifying the absolute configurations of allantoins and probably the Sp stereoisomers, as has been shown previously for other organic molecules.
authors.affiliation: Department of Biology, New York University, New York, New York 10003, USA.
authors.forename: Shuang
authors.initials: S
authors.lastname: Ding
authors.forename: Lei
authors.initials: L
authors.lastname: Jia
authors.forename: Alexander
authors.initials: A
authors.lastname: Durandin
authors.forename: Conor
authors.initials: C
authors.lastname: Crean
authors.forename: Alexander
authors.initials: A
authors.lastname: Kolbanovskiy
authors.forename: Vladimir
authors.initials: V
authors.lastname: Shafirovich
authors.forename: Suse
authors.initials: S
authors.lastname: Broyde
authors.forename: Nicholas E
authors.initials: NE
authors.lastname: Geacintov
mesh_terms: D000481:Allantoin / Q000737:chemistry*; D002942:Circular Dichroism / Q000379:methods*; D006151:Guanosine / Q000031:analogs & derivatives* / Q000737:chemistry; D008968:Molecular Conformation; D009905:Optical Rotatory Dispersion; D013141:Spiro Compounds / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D013141:Spiro Compounds; C408822:spiroiminodihydantoin; D006151:Guanosine; D000481:Allantoin