Regio- and stereocontrolled Diels-Alder reaction tethered by Asp-Thr dipeptide.
The Asp-Thr tethered Diels-Alder reaction of 1a was accomplished to provide 2a exclusively in a regio- and stereoselective manner.
Aspartic Acid↗
Biomedical subjects
Susumu Kawauchi
Publications and source records attributed to Susumu Kawauchi.
Production and excited state dynamics of the photorearranged isomer of benzyl chloride and its methyl derivatives studied by stepwise two-color laser excitation transient absorption and time-resolved thermal lensing techniques.
Production and photoexcited dynamics of reaction intermediates with photolyses of benzyl chloride (BzCl) and methyl-substituted benzyl chlorides (MeBzCls) were studied by using stepwise two-color laser excitation transient absorption (TC-TA) and two-color laser excitation time-resolved thermal lensing (TC-TRTL) measurements. With photoexcitation of BzCl the formation of transient photorearranged isomer was suggested in the previous paper [Res. Chem. Intermed. 2001, 27, 137]. Such an isomer formation for MeBzCls was also observed in a 248 nm excitation. It was found that further photoexcitation of the isomers with the 308 nm light caused photodissociation to yield the corresponding benzyl radicals. The reaction quantum yield and the molar absorptivity of the photorearranged isomer of BzCl were estimated. The heat of reaction for the photodissociation of the isomer was successfully determined with the TC-TRTL measurement. These experimental results were consistent with MO calculations.
Journal Article↗
Computational evaluation of the specific interaction between cation and mismatch base pair.
Ab initio calculations were carried out to characterize the structure and energetic of silver cation (Ag (I)) complex with cytosine (C:Ag:C) and mercury cation (Hg (II)) complex with thymine (T:Hg:T) systems. These metal-modified mismatch base pairs have been optimized using Hatree-Fock method without any symmetry constrains. Using above methods, the models of Ag (I) in a crosslink between O2 carbonyl oxygen of cytosine, O2(C):Ag:O2(C), and Hg (II) in a crosslink between N3 nitrogen atom of thymine, N3(T):Hg:N3(T) were obtained. Furthermore, the interaction energies of C:Ag:C and T:Hg:T models were estimated. The result showed that the coordination silver (I) cation with cytosine is more stable than hydrate state.
Base Pair Mismatch↗
Specific swelling behaviors of poly(4-vinyl phenol) gels in tetraalkylammonium chloride solutions.
Swelling behaviors of poly(4-vinyl phenol) (P4VPh) gel in aqueous tetraalkylammonium chloride (TAACl) solutions were investigated to find a very specific swelling behavior. Especially for the tetrabutylammonium chloride (TBACl) system, P4VPh gel remarkably deswelled with increasing salt concentration (</=2.0 M) and then sharply reswelled in a higher concentration region (>/= ca. 2.1 M). A similar swelling profile was also observed in the swelling time-course; upon immersion of a water-swollen P4VPh gel into 2.5 M TBACl solution, the gel first deswelled in an early stage (approximately 0.1 h) and then remarkably reswelled with time. Relative amounts (mol/mol) of TBA cation and water per monomer residue were estimated as ca. 1 and 0 for the deswollen state and 5 and 50 for the reswollen state, respectively. This result, together with those of attenuated total reflection Fourier transform infrared measurements performed for the gels swollen in various kinds of TAACl and inorganic salt solutions, suggested that in the highly deswollen and almost dehydrated state, phenol rings aggregated with intervening TBA cations, while the aggregation reswelled upon further binding with TBA cations.
Journal Article↗