Versatile Synthesis of Chlorophylls and Bacteriochlorophylls for Fundamental Studies in Photosynthesis

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With the support of the Chemical Synthesis (SYN) program in the Division of Chemistry, Professor Jonathan S. Lindsey at North Carolina State University is developing methods to create chlorophylls and bacteriochlorophylls in the laboratory from simple starting materials. The chemical synthesis of (bacterio)chlorophylls has never been fully accomplished from simple starting materials, although individual steps of a very long pathway to chlorophyll a have been achieved. The goal of this research will allow chlorophylls and analogues to be created in a straightforward manner. The analogues ultimately sought (and their impact areas) will afford a much deeper understanding of energy flow in photosynthesis (biophysics, plant sciences), the nature of metabolic breakdown products (ecology, global carbon balance), and the properties of such compounds (nutrition, medicine). The project lies at the heart of organic chemistry but will also impact diverse areas of science including understanding of photosynthesis. Thus, the project is well suited for the education of scientists at all levels. Professor Lindsey's group is also well positioned to provide the highest level of education and training for students underrepresented in science. Outreach activities involving North Carolina teachers will also be part of the funded project. Chlorophylls and bacteriochlorophylls are the chief pigments in photosynthetic organisms, including plants, cyanobacteria, and anoxygenic photosynthetic bacteria. The lack of synthetic methods for preparing (bacterio)chlorophylls and analogues constitutes an intellectual and technical deficit in the photosynthetic sciences. The Lindsey lab proposes to fill this chasm by developing robust methods for synthesis of such valuable macrocycles. The particular challenges in synthesizing (bacterio)chlorophylls include (1) the stereochemistry of substituents in the pyrroline ring(s), (2) the fifth (isocyclic) ring, and (3) substituents arrayed about the perimeter of the macrocycle. The intellectual merit of the work concerns the development of routes for the synthesis of the key photosynthetic pigments and analogues; the latter have broad impact (beyond the scope of the present grant) encompassing studies of quantum coherence in photosynthesis and catabolism in ecology. A key outcome is a methodology in heterocyclic chemistry for preparing pyrroles, pyrrolines, and hydrodipyrrins relevant to the (bacterio)chlorophylls of photosynthesis. The broader impacts entail professional development of high school science teachers to improve teaching of photosynthesis (via a chlorophyll-based experiment) in schools and to inspire high school students to science, technology, engineering, and mathematics (STEM), thereby broadening the participation of underrepresented groups.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.