Chirality effects on the IRMPD spectra of basket resorcinarene/nucleoside complexes.
The IRMPD spectra of the ESI-formed proton-bound complexes of the R,R,R,R- and S,S,S,S-enantiomers of a bis(diamido)-bridged basket resorcin[4]arene (R and S) with cytosine (1), cytidine (2), and cytarabine (3) were measured in the region 2800-3600 cm(-1). Comparison of the IRMPD spectra with the corresponding ONIOM (B3LYP/6-31(d):UFF)-calculated absorption frequencies allowed the assessment of the vibrational modes that are responsible for the observed spectroscopic features. All of the complexes investigated, apart from [R⋅H⋅3](+), showed similar IRMPD spectra, which points to similar structural and conformational landscapes. Their IRMPD spectra agree with the formation of several isomeric structures in the ESI source, wherein the N(3)-protonated guest establishes noncovalent interactions with the host amidocarbonyl groups that are either oriented inside the host cavity or outside it between one of the bridged side-chains and the upper aromatic nucleus. The IRMPD spectrum of the [R⋅H⋅3](+) complex was clearly different from the others. This difference is attributed to the effect of intramolecular hydrogen-bonding interactions between the C(2')-OH group and the aglycone oxygen atom of the nucleosidic guest upon repulsive interactions between the same oxygen atom and the aromatic rings of the host.
Dipartimento di Chimica e Tecnologie del Farmaco, Università di Roma La Sapienza, 00185 Roma, Italy.
Antonello
A
Filippi
Caterina
C
Fraschetti
Susanna
S
Piccirillo
Flaminia
F
Rondino
Bruno
B
Botta
Ilaria
I
D'Acquarica
Andrea
A
Calcaterra
Maurizio
M
Speranza
D003561:Cytarabine / Q000737:chemistry; D003562:Cytidine / Q000737:chemistry; D003596:Cytosine / Q000737:chemistry; D015394:Molecular Structure; D009705:Nucleosides / Q000737:chemistry*; D011522:Protons; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013237:Stereoisomerism
D009705:Nucleosides; D011522:Protons; D003561:Cytarabine; D003562:Cytidine; D003596:Cytosine