Synthetic approaches to structurally complex molecules by photo- and non-photochemical methods

Hyunil Jo, University of Pennsylvania

Abstract

This dissertation details the development and investigation of three independent research projects. These aims show a progressive evolution from ground state chemistry to excited state chemistry and finally supramolecular chemistry in construction and design of structurally complex molecules. The first section shows the synthetic approaches toward a potent microtubule stabilizing natural product, elutherobin, utilizing tandem Diels-Alder reaction/Grob-type fragmentation reaction as key steps. During the course of these studies, large scale preparation of bis-diene and successful activation of the secondary alcohol were achieved. Due to the difficulty in SmI 2 fragmentation and the capricious nature of the tandem Diels-Alder reaction, our original route did not prove amenable to an efficient synthesis of eleutherobin. A revised route using a β-elimination pathway was subsequently investigated. The following section has its foundation based upon a serendipitous discovery in the Winkler group. In an effort to explore the scope of the photoreaction, we found a novel desulfurative photocycloaddition from investigation of enone-benzothiazoline photochemistry and its mechanistic rationale was studied to suggest enecarbamate could be an intermediate that was generated from its episulfide precursor. The formation of N,S-acetal photoproduct could be also utilized in the synthesis of another natural product, discorhabdin A. The concluding section deals with a synthetic design of chiral molecular tweezers based upon the natural alkaloid calycanthine. A number of synthetic strategies on the extended dimer of calycanthine were investigated and monobromocalycanthine was successfully prepared from a semi-synthetic approach. The future directions of this project based on dimethylcalycanthine are presented.

Subject Area

Organic chemistry

Recommended Citation

Jo, Hyunil, "Synthetic approaches to structurally complex molecules by photo- and non-photochemical methods" (2008). Dissertations available from ProQuest. AAI3346138.
https://repository.upenn.edu/dissertations/AAI3346138

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