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As a physical-organic chemist with a focus in photochemistry, in this literature, I will be studying the reactivity of organic azido-quinones upon light irradiation in solution and solid-state. Azides, after irradiation, gives access to high spin assembly nitrenes that can generate compounds hard to obtain through normal synthetic routes. In the solid-state, we developed crystalline solids, due to their pristine crystal lattice giving rise to regioselectivity, then upon irradiation, also producing compounds that would otherwise be hard to obtain. These crystals, with the naked-eye or under microscope, will display some mechanical motion after light exposure. In my work, bromine derivatives will be used to stabilize azirine or used during crystallization to alter the photodynamic effect displayed. Photomechanical motions aren’t only about looking at the crystal’s nice movements, but due to their ability to harvest the energy from the light, it opens up the possibility to the innovation of new devices.

Quinones are ubiquitous in biochemistry, where they typically function as electron carriers in processes such as photosynthesis and respiration. Quinones bound in protein complexes are often studied using Fourier-transform infrared (FTIR) difference spectroscopy (DS). With FTIR DS it is possible to probe even small changes in hydrogen bonding between the quinones and nearby protein residues. However, the interpretation of FTIR DS is complicated by multiple overlapping contributions to the spectra. Here we employ density functional theory (DFT) based vibrational frequency calculations on benzoquinone (BQ) and naphthoquinone (NQ) model systems to help untangle the intrinsic and environmental factors that could shift the quinone’s vibrational mode frequencies and intensities. Specifically, we systematically study the effect that hydrogen bonds and quinone substituents have on the ��=�� mode vibrational frequencies of the neutral and one-electron reduced BQs and NQs.

In photosystem I (PSI), the secondary electron acceptor is a phylloquinone (PhQ) molecule and occupies the so-called A1 binding site. PhQ, a naphthoquinone derivative with methyl and phytyl substituents, forms a single hydrogen bond (H-bond) via one carbonyl oxygen to the protein in PSI. Light-induced Fourier-transform infrared (FTIR) difference spectra corresponding to electron acceptor A1 in PSI protein complex reconstituted with non-native quinones show the influence of the quinone-protein interactions in terms of vibrational modes. However, the interpretation of FTIR difference spectra is not straightforward; in particular, the origin of two noticeable separated carbonyls vibrational modes in the anionic states has not been elucidated. Theoretical spectra built upon the X-ray crystal structure using the multi-layer ONIOM technique have been developed to assist the assignment of FTIR bands associated with native and foreign quinones in the A1 binding site. Calculated and FTIR spectra remarkably agree when the H-bond network, including water molecules in the H-bonded carbonyl vicinity, is included in the molecular structure. The conformity suggests that the complex H-bond network between water molecules might modulate the vibrational bands of reduced PhQ (PhQ-) in the A1 binding site; consequently, quinones' observed splits between carbonyls vibrational modes in the A1 binding site are simulated. Furthermore, theoretical models along with experiments indicate that non-native quinones adopt a particular orientation with respect to the presence of the single H-bond in the protein in addition to their chemical structures and related substituents. Comparison between vibrational bands of PhQ- in the A1 binding site in PSI and the QA binding site of purple photosynthetic bacteria indicates that the unique H-bond pattern in the anionic state is the structural feature of the A1 binding site. In comparison, the formation of two H-bond interactions via carbonyl oxygen atoms of PhQ- in the QA binding site does not lead to the noticeable split and shift between two carbonyl vibrations. In contrast to the A1 binding site, calculations show that a polar and aprotic solvent model could be appropriate to simulate PhQ- and protein interactions in the QA binding site.

As part of an International Cooperative Biodiversity Group (ICBG) program and a continuing search for antiproliferative natural products from the Madagascar rainforest, and a collaborative research project established between Virginia Tech and the Institute for Hepatitis and Virus Research (IHVR) focusing on searching for bioactive natural products from tropical forests in South Africa, 20 extracts were selected for investigation based on their antiproliferative activities against A2780 human ovarian cancer cell line or antimalarial activities against the Dd2 strain of Plasmodium falciparum. Bioassay-guided fractionation of seven of the extracts yielded twenty new compounds and twenty-four known compounds, and their structures were elucidated by using a combination of 1D (1H and 13C) and 2D NMR spectroscopy including COSY, HASQC, HMQC, HMBC, and NOESY sequences, mass spectrometry, UV, IR, ECD, optical rotation, and chemical conversions. In addition, ten known compounds were isolated from another five of the extracts, while studies on the remaining extracts were suspended due to loss of activity, unworkable small amounts of material, or low structural interest. The plants and their metabolites are discussed in the following order: five new antimalarial 5,6-dihydro--pyrones and six bicyclic tetrahydro--pyrone derivatives from Cryptocarya rigidifolia (Lauraceae); two new and five known antiproliferative lignans from Cleistanthus boivinianus (Phyllanthaceae); two new and two known antiproliferative sesquiterpenes lactones from Piptocoma antillana (Asteraceae); one new antiproliferative 1,4-naphthoquinone, one known antiproliferative isoflovonoid, and five known antiproliferative stilbenoids from Stuhlmannia moavi (Leguminosae); four known antiproliferative bisbenzylisoquinoline alkaloids from Anisocycla grandidieri (Menispermaceae); one new and two known antiproliferative butanolides, and two new antiproliferative secobutanolides from Ocotea macrocarpa (Lauraceae); one new antiproliferative and five known antiproliferative diterpenoids from Malleastrum rakotozafyi (Meliceae); and 10 known compounds from Monoporus sp. (Myrsinaceae), Premna corymbosa (Verbenaceae), Premna perplexanes (Verbenaceae), Epallage longipes (Asteraceae), and Cinnamosma fragrans (Canellaceae).

The study of some acylurea derivatives of 2-amino-3-alkylamino- and -3-arylamino-1,4-naphthoquinones was undertaken to determine the course of reaction under conditions similar to those used by J. R. Hoover and A. R. Day to prepare 2-alkyl-1H-naphth[2,3-d] imidazole-4.9-diones from 2-acylamino-3-amino-1,4-naphthoquinones.

Although many quinoid pigments are known, until recently only six naphthoquinone pigments had been isolated from animals and identified. However in 1966, Moore, Singh and Scheuer reported the isolation of over thirty different pigments from the sea urchins Echinothrix diadema Linn. and E. calamaris Pallis. In addition to five known compounds, eleven new pigments were identified. Several of these pigments were juglone derivatives containing hydroxyl and acetyl functions. The synthesis of only three acetyljuglone derivatives has been described previously. This paucity of data showed the need for further work in this area. For this reason and in order to facilitate structure proof of several new pigments, the introduction of hydroxyl and acetyl groups into juglone and several of its derivatives was investigated. As a result of this work the structures of three pigments (i, ii, iii) were confirmed, but a fourth compound (iv) did not display identical properties with those of the natural pigment. In addition to the synthesis of compounds i-iv, five new juglone derivatives (v-ix) were prepared. Compounds v-ix have not yet been reported as naturally occurring substances. Investigation of new methods for the synthesis of juglone and naphthazarin derivatives was unsuccessful.