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You searched for +publisher:"Florida International University" +contributor:("David A. Becker"). Showing records 1 – 3 of 3 total matches.

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Florida International University

1. Birudukota, Nagaraju. Design and synthesis of novel Azasteroids and Pseudoazulenyl nitrones.

Degree: PhD, Chemistry, 2016, Florida International University

Steroids are one of the essential classes of bioactive compounds and are involved in many biological functions which include their role as signaling compounds, the alteration of membrane fluidity and the regulation of a variety of metabolic processes. In order to identify novel compounds with beneficial pharmacological action, the synthesis of modified steroids is gaining much attention in recent years. Among those analogs, azasteroids are one of the most important classes which display a variety of biological activities, often free from undesirable side effects. The challenges in the synthesis of steroids, particularly azasteroids, and the potential of azasteroids as novel drugs has prompted numerous investigations in this field. The synthetic methods leading to steroidal derivatives (azasteroids) with one or more nitrogen atoms are very limited. Generally, oxidative cleavage of the steroidal rings is needed to introduce nitrogen atom(s) in order to synthesize azasteroids. In the first part of this dissertation, explorations into the synthetic methods needed for making a new steroidal A-ring or seco A-ring on a tricyclic benz[e]indenedione (a dimer compound obtained in connection with continued work on the study of anhydrobases of the isoxazole series) were pursued. In this process, a series of three tricyclic hydrazone compounds have been designed and synthesized to mimic the tetracyclic rigid core structure of azasteroids. We are eager to ascertain if these compounds possesses any interesting biological properties. In continued research on the synthesis of azulenyl and pseudoazulenyl nitrones, (to target ROS generation at the site of mitochondria), the second part of this research was aimed at the synthesis of cationic pseudoazulenyl nitrones with mitochondriotropic properties. Several pseudoazulenyl nitrone derivatives were synthesized using the natural compound valtrate, obtained from the roots of Centranthus ruber. Unfortunately, the attempts made to convert these compounds into the corresponding cationic pseudoazulenyl nitrones failed. However, an interesting pseudoazulenyl dinitrone molecule bearing an imidazole group was prepared. Also, a pseudoazulenyl mono nitrone compound with an electron donating group was synthesized by leaving a highly reactive aldehyde functionality intact for further use in synthetic study. Advisors/Committee Members: David A. Becker, Stanislaw F. Wnuk, Kevin O'Shea, Anthony P. DeCaprio, Richard A. Bone.

Subjects/Keywords: Synthesis; Azasteroids; Azasteroidal mimics; Azulenes; Azulenyl nitrones; Pseudoazulenes; Pseudoazulenyl nitrones; Biochemistry; Chemistry; Organic Chemistry

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APA (6th Edition):

Birudukota, N. (2016). Design and synthesis of novel Azasteroids and Pseudoazulenyl nitrones. (Doctoral Dissertation). Florida International University. Retrieved from https://digitalcommons.fiu.edu/etd/3262 ; 10.25148/etd.FIDC001734 ; FIDC001734

Chicago Manual of Style (16th Edition):

Birudukota, Nagaraju. “Design and synthesis of novel Azasteroids and Pseudoazulenyl nitrones.” 2016. Doctoral Dissertation, Florida International University. Accessed March 08, 2021. https://digitalcommons.fiu.edu/etd/3262 ; 10.25148/etd.FIDC001734 ; FIDC001734.

MLA Handbook (7th Edition):

Birudukota, Nagaraju. “Design and synthesis of novel Azasteroids and Pseudoazulenyl nitrones.” 2016. Web. 08 Mar 2021.

Vancouver:

Birudukota N. Design and synthesis of novel Azasteroids and Pseudoazulenyl nitrones. [Internet] [Doctoral dissertation]. Florida International University; 2016. [cited 2021 Mar 08]. Available from: https://digitalcommons.fiu.edu/etd/3262 ; 10.25148/etd.FIDC001734 ; FIDC001734.

Council of Science Editors:

Birudukota N. Design and synthesis of novel Azasteroids and Pseudoazulenyl nitrones. [Doctoral Dissertation]. Florida International University; 2016. Available from: https://digitalcommons.fiu.edu/etd/3262 ; 10.25148/etd.FIDC001734 ; FIDC001734


Florida International University

2. Rayala, Ramanjaneyulu. Design and Synthesis of Novel Nucleoside Analogues: Oxidative and Reductive Approaches toward Synthesis of 2'-Fluoro Pyrimidine Nucleosides.

Degree: PhD, Chemistry, 2015, Florida International University

Fluorinated nucleosides, especially the analogues with fluorine atom(s) in the ribose ring, have been known to exert potent biological activities. The first part of this dissertation was aimed at developing oxidative desulfurization-fluorination and reductive desulfonylation-fluorination methodologies toward the synthesis of 2'-mono and/or 2',2'-difluoro pyrimidine nucleosides from the corresponding 2'-arylthiopyrimidine precursors. Novel oxidative desulfurization-difluorination methodology was developed for the synthesis of α,α-difluorinted esters from the corresponding α-arylthio esters, wherein the arylthio group is present on a secondary internal carbon. For the reductive desulfonylation studies, cyclic voltammetry was utilized to measure the reduction potentials at which the sulfone moiety of substrates can be cleaved. The 5-bromo pyrimidine nucleosides and 8-bromo purine nucleosides act as crucial intermediates in various synthetic transformations. The second part of the present dissertation was designed to develop a novel bromination methodology using 1,3-dibromo-5,5-dimethylhydantoin (DBH). Various protected and deprotected pyrimidine and purine nucleosides were converted to their respective C5 and C8 brominated counterparts using DBH. The effect of Lewis acids, solvents, and temperature on the efficiency of bromination was studied. Also, N-bromosuccinimide (NBS) or DBH offered a convenient access to 8-bromotoyocamycin and 8-bromosangivamycin. Third part of this research work focuses on the design and synthesis of 6-N-benzylated derivatives of 7-deazapurine nucleoside antibiotics, such as tubercidin, sangivamycin and toyocamycin. Target molecules were synthesized by two methods. First method involves treatment of 7-deazapurine substrates with benzylbromide followed by dimethylamine-promoted Dimroth rearrangement. The second method employs fluoro-diazotization followed by SNAr displacement of the 6-fluoro group by a benzylamine. The 6-N-benzylated 7-deazapurine nucleosides showed type-specific inhibition of cancer cell proliferation at micromolar concentrations and weak inhibition of human equilibrative nucleoside transport protein (hENT1). In the fourth part of this dissertation, syntheses of C7 or C8 modified 7-deazapurine nucleosides, which might exhibit fluorescent properties, were undertaken. 8-Azidotoyocamycin was synthesized by treatment of 8-bromotoyocamycin with sodium azide. Strain promoted click chemistry of 8-azidotoyocamycin with cyclooctynes gave the corresponding 8-triazolyl derivatives. Alternatively, 7-benzotriazolyl tubercidin was synthesized by iodine catalyzed CH arylation of tubercidin with benzotriazole. Advisors/Committee Members: Stanislaw F. Wnuk, Kathleen S. Rein, David A. Becker, Anthony P. DeCaprio, Salvatore D. Lepore.

Subjects/Keywords: Fluorination; Desulfurization; Desulfonylation; Pyrimidines; Purines; 7-Deazapurines; DBH; Click Chemistry; C-H Functionalization; One Electron Oxidation; Carbohydrates; Heterocyclic Compounds; Nucleic Acids, Nucleotides, and Nucleosides

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Rayala, R. (2015). Design and Synthesis of Novel Nucleoside Analogues: Oxidative and Reductive Approaches toward Synthesis of 2'-Fluoro Pyrimidine Nucleosides. (Doctoral Dissertation). Florida International University. Retrieved from https://digitalcommons.fiu.edu/etd/2172 ; 10.25148/etd.FIDC000129 ; FIDC000129

Chicago Manual of Style (16th Edition):

Rayala, Ramanjaneyulu. “Design and Synthesis of Novel Nucleoside Analogues: Oxidative and Reductive Approaches toward Synthesis of 2'-Fluoro Pyrimidine Nucleosides.” 2015. Doctoral Dissertation, Florida International University. Accessed March 08, 2021. https://digitalcommons.fiu.edu/etd/2172 ; 10.25148/etd.FIDC000129 ; FIDC000129.

MLA Handbook (7th Edition):

Rayala, Ramanjaneyulu. “Design and Synthesis of Novel Nucleoside Analogues: Oxidative and Reductive Approaches toward Synthesis of 2'-Fluoro Pyrimidine Nucleosides.” 2015. Web. 08 Mar 2021.

Vancouver:

Rayala R. Design and Synthesis of Novel Nucleoside Analogues: Oxidative and Reductive Approaches toward Synthesis of 2'-Fluoro Pyrimidine Nucleosides. [Internet] [Doctoral dissertation]. Florida International University; 2015. [cited 2021 Mar 08]. Available from: https://digitalcommons.fiu.edu/etd/2172 ; 10.25148/etd.FIDC000129 ; FIDC000129.

Council of Science Editors:

Rayala R. Design and Synthesis of Novel Nucleoside Analogues: Oxidative and Reductive Approaches toward Synthesis of 2'-Fluoro Pyrimidine Nucleosides. [Doctoral Dissertation]. Florida International University; 2015. Available from: https://digitalcommons.fiu.edu/etd/2172 ; 10.25148/etd.FIDC000129 ; FIDC000129

3. Cui, Wenbin. Comparative Evaluation on Human Infants Dietary Mercury Exposure through Consumption of Fish and Rice Products.

Degree: PhD, Chemistry, 2017, Florida International University

Human exposure to methylmercury (MeHg) through diets (e.g., fish and rice) is a global health concern. Although MeHg exposure through fish consumption has long been considered the major route of mercury health risks, studies concerning the long-term changes in MeHg exposure from fish remain lacking. In sharply contrast to the fish MeHg issue, the presence of MeHg in rice has only been reported recently and its implications on MeHg exposure, albeit probably important, are still in infancy. Focusing on the discrepancies in the studies of MeHg exposure through fish and rice consumption, this study was aimed to assess the MeHg exposure of human infants through consumption of rice cereals and to evaluate the long-term changes in fish MeHg. The presence of MeHg in rice prompted the studies on MeHg concentrations and bioaccessibility in rice cereals and potential infant dietary exposure to MeHg through cereal consumption, which is believed to be the first of its kind. The analysis of a variety of infant cereals sampled from the common markets in the United States and China showed that the concentrations of MeHg in the cereals ranged from 0.07 to 13.9 µg/kg with a mean of 1.61 µg/kg. On the basis of these MeHg concentrations, the daily intake of MeHg through rice cereal consumption for infants was estimated to be 4-122% of the reference dose (RfD). The MeHg bioaccessibility in the cereals, determined using an in vitro digestion method, ranged from 25 to 74% with a mean of 48±16%. A further examination on these results, however, revealed the occurrence of MeHg re-adsorption during extraction steps, which leads to the underestimation of MeHg bioaccessibility and warrants cautions to be exercised when using these procedures to evaluate bioaccessibility in general. The long-term changes in fish MeHg were investigated through conducting a comprehensive data analysis on datasets for the Everglades, a well-studied aquatic ecosystem for Hg contamination. The results showed a clear decline of MeHg in mosquitofish in the Everglades during the past two decades, which was probably related to changes in environmental conditions (e.g., periphyton, dissolve organic matter, and sulfate) instead of mercury deposition. Advisors/Committee Members: Yong Cai, José R. Almirall, David A. Becker, Jin He, Rudolf Jaffé.

Subjects/Keywords: Methylmercury; rice cereal; dietary exposure; reference daily dose; health risk; Everglades; fish; periphyton; environmental parameters

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Cui, W. (2017). Comparative Evaluation on Human Infants Dietary Mercury Exposure through Consumption of Fish and Rice Products. (Doctoral Dissertation). Florida International University. Retrieved from https://digitalcommons.fiu.edu/etd/3464 ; 10.25148/etd.FIDC001932 ; FIDC001932

Chicago Manual of Style (16th Edition):

Cui, Wenbin. “Comparative Evaluation on Human Infants Dietary Mercury Exposure through Consumption of Fish and Rice Products.” 2017. Doctoral Dissertation, Florida International University. Accessed March 08, 2021. https://digitalcommons.fiu.edu/etd/3464 ; 10.25148/etd.FIDC001932 ; FIDC001932.

MLA Handbook (7th Edition):

Cui, Wenbin. “Comparative Evaluation on Human Infants Dietary Mercury Exposure through Consumption of Fish and Rice Products.” 2017. Web. 08 Mar 2021.

Vancouver:

Cui W. Comparative Evaluation on Human Infants Dietary Mercury Exposure through Consumption of Fish and Rice Products. [Internet] [Doctoral dissertation]. Florida International University; 2017. [cited 2021 Mar 08]. Available from: https://digitalcommons.fiu.edu/etd/3464 ; 10.25148/etd.FIDC001932 ; FIDC001932.

Council of Science Editors:

Cui W. Comparative Evaluation on Human Infants Dietary Mercury Exposure through Consumption of Fish and Rice Products. [Doctoral Dissertation]. Florida International University; 2017. Available from: https://digitalcommons.fiu.edu/etd/3464 ; 10.25148/etd.FIDC001932 ; FIDC001932

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