Santhosh Penta

Synthesis of 4-aryl-2-pyranyl-7,8-dihydroquinolin-5(6 H )-ones catalyzed by cerium ammonium nitrate via Hantzsch multicomponent reaction and their antibacterial activity

4-Aryl-2-pyranyl-7,8-dihydroquinolin-5(6H)-one derivatives were obtained in excellent yields from 3-acetyl-4-hydroxy-6-methyl-2Hpyran-2-one, aromatic aldehydes, 5,5-dimethylcyclohexane-1,3-dione, and ammonium acetate by a one-pot multicomponent Hantzsch synthesis in the presence of cerium ammonium nitrate in water. In vitro antibacterial activity of all the newly synthesized compounds was evaluated. Some of the tested compounds showed a promising antibacterial activity against both Gram-positive and Gram-negative bacterial strains.

Copper(II)nitrate catalyzed regioselective protection of primary alcohols with 4,4′-dimethoxytrityl and 2,7-dimethyl-9-phenyl xanthen-9-yl groups in nucleosides and carbohydrates

ABSTRACT Regioselective protection of primary hydroxyl group in nucleoside and carbohydrate analogs was accomplished using dimethoxytrityl alcohol (DMTr-OH) or dimethylpixyl alcohol (DMPx-OH) in presence of copper(II)nitrate as a Lewis acid catalyst. Excellent selectivity was observed for the protection of primary hydroxyl group over secondary while glycosidic bond remain unaffected. Utility of this methodology was further exemplified via DMTr- and DMPx-protection of alipahtic acyclic and cyclic diols.

Recent developments in synthesis of embelin heterocyclic derivatives and their biological applications

Embelin (2,5-dihydroxy-3-undecyl-1,4-benzoquinone) has attracted a great deal of synthetic attention as a biologically active heterocyclic compound in the last decades. The high reactivity of its carbonyl groups, active methylene group, and hydroxyl groups represents challenges to many organic reactions for the synthesis of various embelin derivatives. This review summarizes for the first time the most recent and relevant approaches towards the synthesis of embelin-linked heterocyclic derivatives.

Ring Transformations in Dehydroacetic Acid

Abstract Dehydroacetic acid undergoes several kinds of reactions. Of these, ring transformations are having much more importance in organic synthesis. Most of the compounds formed by ring transformations of DHA are five-membered rings. When we see the mechanism of these transformations, we can observe the opening of a pyran ring into 1,3-di-carbonyl compound as an intermediate and then transforming into five- or six-membered heterocyclics. In this chapter we will discuss the formation of different hetero cyclic compounds from DHA by ring transformation reactions.

Chapter 3 – Antitumor Agents

This chapter describes the structure-activity relationships (SARs) of various coumarin derivatives having antitumor activity, which are considered for proficient inhibitors over the various human cancer cell lines. Antitumor agents: Coumarins substituted with hydroxyl, cyclopentane, and alkoxy groups are effective antitumor agents. At C3 position substitution of a hydroxyl group, amine group with palladium complex, hydrazide-hydrazone moiety having different heterocyclic group, sulphonamide derivatives are effective in the inhibition of various cancerous cell lines. Similarly, at C4 position, hydroxyl groups, tosyl groups, triazole groups with alkoxy aromatic rings and hydrogen bond acceptor groups, and idophenol derivatives with different substitutions are effective. Fused benzosubernone rings and furan rings at C3-C4 position and the presence of hydroxyl groups and alkoxy groups at C5 position are effective. At C6 position, hydroxyl groups, methylenedioxy groups, and chlorine atoms are significant. Finally, at C7 position, hydroxyl groups, chlorine atoms, amide derivatives, methoxy groups, and aromatic sulphonate derivatives showed effective antitumor activity.

Introduction to Coumarin and SAR

Structure-based drug design is a quickly emerging field, with achievements to a large extent of anticipation in recent years. Improvements in structural information and the mechanism of biological interactions have delivered several new targets and opportunities to create new drugs, leading to discovery. In medicinal and pharmacological studies, coumarins are well known for their highly potent biological activity as well as their versatility. Structure-activity relationships (SARs) of the coumarin derivatives with different substituents in various positions reveals significant information related to the development of highly specified and potent drugs. This chapter is intended as an overview of and introduction to coumarin and the process of drug designing as well as the application of structure-activity relationships, starting from the selection of the target to the generation and development of the lead compound.

Chapter 2 – Antimicrobial Agents

Coumarin derivatives are among the most intensely examined class of compounds in consideration of a proficient effective drug for microbial diseases. This chapter describes the structure-activity relationships (SARs) of coumarin derivatives associated with the various functional groups and position of coumarin for its antibacterial, antivirus, and antifungal activity. Antibacterial agents: At C3 position on the coumarin ring, the presence of ethylene moiety with carboxylic or tertiary amines group, alkoxyimino group, carbonyl group, hydroxamate group, and benzyl group with hydroxyl or halide group substitution is effective. Similarly, at C4 position, the methyl group, halogen-substituted iodinated aryloxymethyl group, thiotriazo derivatives are effective. Nitro group at C5 position is active. Whereas at C7 position, the carbomoyl group, complex alkoxy group substituted with electron withdrawing group, biphenyl groups are significant. Furanocoumarin substituted with nitro group, and at C8 position methyl group is effective for antibacterial activity. Antiviral agents: Planarity of coumarin ring and methyl group substitution on coumarin ring are important for antiviral agents. Methyl-substituted benzimidazole nucleus or D-ribofuranose group at C3 position of coumarin showed the prominent antiviral activity. Substituted heterocyclic group with -SCH2 linkage was also found as important for bioactivity. Antifungal agents: For effective antifungal activity, nitro group at C3 position is significant, whereas at C4 position the acetyl group is effective. At C6 position both nitro and acetyl groups are active, and at C7 position, the small alkoxy aliphatic chain, phenyl group, acetyl group, and nitro group are prominent.