Abstract
This thesis includes three parts: the potential energy surface corresponding to the Ramachandran plot, the 1,3-dipolar cycloaddition reactions of acetonitrile oxide with 5-substituted adamantan-2-one and its derivatives, and the structure effects on the Myers-Satio reaction. In the study of Ramachandran plot, the backbone energy of glycine was estimated using a model molecule with the B3LYP/D95++** method. The beta and beta'-sheets distribute at the ranges of energy lower than 2 kcal/mol. The alpha-helix and collagen structures are at higher energy regions of 5 ~ 7 kcal/mol. Thus, the backbone energy of most amino acids in proteins are concluded to be lower than 7 kcal/mol. The face selectivity of the 1,3-dipolar cycloaddition system was studied by the BLYP and BPW91 method with the 3-21G** basis set. Although the basis set is too small to accurately predict comparable results with experiments, the structural difference can still offer some useful information. The hyper conjugation effect exists in the adamantan-2-one and its derivatives; therefore, the four CC bonds near the C=Y (Y = O, S and CH2) groups have longer bond lengths, about 1.57 ~ 1.58 angstroms. The most important interaction that determines the face selectivity of this reaction is the hyperconjugation destruction from the reactants to the transition structures. The BPW91/6-311G** method are employed for studying the Myers-Satio reaction. The ring structure of the reactants lowers the activation energy and reduces the temperature effect on the thermodynamic data. The through bond interaction plays a significant role in the reaction 10 of a nine-membered ring compound. The reactivity of reaction 10 is similar to the Bergman reaction instead of the general Myers-Satio reaction due to the strong through bond interaction. Thus, 10 can be a reaction center of certain Bergman anti-tumor drug. A straightforward method to determine whether a reaction has the early or the late transition structure by the change of entropy was also derived. The late transition structures of Myers-Satio reactions confirm the validity of this method. The reaction centers of the Bergman anti-tumor drugs have very similar (Delta)Sa : (Delta)S ratio, 0.90 ~ 0.94 at 310.65 K, so they can almost have the same reactivity.