Associate Professor and Vice Chair Undergraduate Program
Research Synopsis: Host-guest chemistry and peptide chemistry
Host-Guest Chemistry; Supramolecular Chemistry; Design and Synthesis of Molecular Containers; Inner Phase Chemistry and Catalysis; Reactive Intermediates; Strained Hydrocarbons; De Novo Design of Helical Peptides; Conformationally Constrained Amino Acids; Peptide-based Ion-Channels; Photochemical Triggers for Protein Folding
Host-Guest isolation of reactive intermediates: 1,2,4,6-cycloheptatetraene
The enantiomerization of 1,2,4,6-cycloheptatetraene (CHTE) in the inner phase of a chiral hemicarcerand. The enantiomerization of CHTE via the planar cycloheptatrienylidene (CHT) as the transition state is an important part of the phenylcarbene rearrangement. Recently, we generated CHTE photochemically in the inner phase of a chiral hemicarcerand, which prevented the dimerization of the highly strained guest. This allowed us to measure the exchange rate between the two diastereomeric CHTE hemicarceplexes (left and right structures) and to determine the enantiomerization barrier.
Host-Guest isolation of reactive intermediates: o-benzyne
The photochemical generation of o-benzyne in the inner phase of a hemicarcerand (center). Photolysis of incarcerated benzocyclobutenedione yields o-benzyne and two molecules of CO, which escape the inner phase (bottom right bull eye). The surrounding hemicarcerand protected the highly strained o-benzyne from self-destruction, e.g. dimerization, and allowed us to characterize for the first time o-benzyne by liquid phase NMR spectroscopy. Partial 13C-NMR spectra of a fully 13C-labeled o-benzyne are shown in the bull eyes on the left side and in the upper right corner.
Conformationally constrained peptides
A conformationally constrained lysine induces a single alpha helical turn in a short peptide.