Date of Award
Chemistry and Biochemistry
Cecilia H. Marzabadi, Ph.D
James E. Hanson, Ph.D
Gerald J. Buonopane, Ph.D
synthesis, Pyranobenzopyrans, Microwave, Ionic Liquid
Carbohydrates and their derivatives are involved in a wide array of biological processes and are crucial for the survival of living entities. As a result, sugar-based compounds have become attractive scaffolds for drug design. In addition, pyranobenzopyran derivatives have shown promise in the treatment of numerous health conditions such as anticoagulants, antifungal, and anti-inflammatory agents. They have also shown important properties as antibiotics anti-AIDS agents) and antitumor drugs. The main point of our research was to determine and develop a synthetic method for the preparation of pyranobenzopyrans and carbohydrate fused heterocyclic compounds. This was accomplished via a [4+2] cycloaddition reaction to generate the oxygen-containing six-membered ring by the addition of the imine o-hydroxybenzaldimine and its derivatives to glucals in organic solvent under catalysis by scandium triflate. The conventional method and microwave reactor method were initially used to achieve this goal, but no reaction was observed. The failure of these reactions may be due to the sugar protecting group such as the acetyl ester. Acetyl could deactivate electronically, where benzyl and butyldimethylsilyl ethers created steric hindrance and inhibited the reaction. Then new methodology was developed and an ionic liquid was used as a solvent to dissolve the D-glucal and the other reactants. A series of pyranobenzopyrans have been prepared via Lewis Acid catalyzed cycloaddition reactions of D-glucal and o-hydroxybenzaldehyde and its derivatives in room temperature imidazolium ion-based ionic liquid solvents. Different o-hydroxybenzaldehyde derivatives were tested to study the effect of the substituents in the rate of the reaction. Four products were obtained in poor to moderate yields. Because 2-hydroxy-5-nitrobenzaldehyde, 2-hydroxy-5-methylbenzaldehyde and 2,5-dihydroxybenzaldehyde were insoluble in the ionic liquids, no product was obtained from their reaction with D-glucal. Danishefsky’s Diene, 1-methoxy-3-trimethylsiloxy-1, 3-butadiene, was also reacted in ionic liquid and the product 2-5,8a-dihydroxy-1(hydroxymethyl)-1,4a, 5, 6, 7,8a-hexahydro-8H-isochromenone was obtained in moderate yield. In these reactions, the glycal itself was found to serve as a diene with another molecule of glycal as the dienophile to form an interesting sugar dimer. All the structures prepared were confirmed by NMR and elemental analyses.
Eltayeb, Sumiea B., "Synthesis of Pyranobenzopyrans" (2017). Seton Hall University Dissertations and Theses (ETDs). 2302.