Computational studies of reactions of the UV-blocker 3-hydroxykynurenine and of pericyclic reactions of a highly reactive aminoborane

Two sets of computational studies were performed utilizing general electronic structure methods. These studies complement experimental results because they analyze experimental unobservables and they select between products experimentally identified only by spectroscopy.;The first study is of the UV-blocker 3-hydroxykynurenine. Amino acid residues on crystallins react with the UV-blocker 3-hydroxykynurenine, causing the human lens to become yellowed and cloudy with age. This reaction is marked by a decrease in absorbance at 365 nm, a 3-hydroxykynurenine peak, and an increase in absorbance at 320 nm and above 415 nm. Density functional theory optimizations and time dependent-density functional theory calculations performed in this dissertation on 3-hydroxykynurenine and similar molecules yielded models of their structures and the peaks of their absorbance spectra. Upwards of fifty potential photoproducts were researched computationally to aid the mass spectrometry and UV/Vis results. Experimental and calculated physical properties revealed that the attachment of N-terminal lysine is one likely source of a peak at 320 nm. A photoproduct of this type is proposed to be a bio-marker to cataract formation. Meanwhile, other proposed products that could give rise to the peak at 415 nm were examined.;The second study was of pericyclic reactions of a highly reactive aminoborane. Aminoborane (F3C)2BN(CH3)2 undergoes olefin-like bimolecular reactions with substrates in preference to dimerization. This arises from a combination of the steric bulk and the electron accepting/donating properties of the substituents, which enhances the double bond between nitrogen and boron. I examined ene-type and hydride transfer-type pericyclic reactions of (F3C)2BN(CH3)2 with alkenes and alkynes, using density functional and ab initio models. Both reactions proceed through six-membered cyclic chair-like transition states. Results for model reactions indicated that product formation depends on kinetic barriers rather than reaction energies, with a barrier of 65 kJ/mol apparently being the maximum for experimental reactions that occur readily. Experimental reactions where diborylation results from sequential ene steps, and where ene-type and hydride transfer-type reactions compete were also investigated. Observed products and distributions for these correlate with barrier energies. The observed 7:3 product mixture resulting from the reaction between 1-hexyne and (F3C)2BN(CH3)2 matches the 3 kJ/mol barrier difference.