Effective syntheses of quinoline-7,8-diol, 5-amino-l-DOPA, and 3-(7,8-dihydroxyquinolin-5-yl)-l-alanine

The Baeyer–Villiger Oxidation of Cycloketones Using Hydrogen Peroxide as an Oxidant

Baeyer–Villiger oxidation can synthesize a series of esters or lactones that have essential application value but are difficult to be synthesized by other methods. Cycloketones can be oxidized to lactones using molecular oxygen, peroxy acids, or hydrogen peroxide as an oxidant. Hydrogen peroxide is one of the environmental oxidants. Because of the weak oxidation ability of hydrogen peroxide, Bronsted acids and Lewis acids are used as catalysts to activate hydrogen peroxide or the carbonyl of ketones to increase the nucleophilic performance of hydrogen peroxide. The catalytic mechanisms of Bronsted acids and Lewis acids differ in the Baeyer–Villiger oxidation of cyclohexanone with an aqueous solution of hydrogen peroxide as an oxidant.

Synthesis of Proposed Structure of Aaptoline A, a Marine Sponge-Derived 7,8-Dihydroxyquinoline, and Its Neuroprotective Properties in C. elegans

A concise and efficient synthesis of the proposed structure of aaptoline A, a 7,8-dihydroxyquinoline derived from a marine sponge, was accomplished in seven steps with a 52% overall yield. A key feature of the synthesis is the high-yielding Ag(I)-catalyzed cycloisomerization of the N-propargylaniline precursor to afford the quinoline carboxylate skeleton from acid-labile methyl aminobenzoate. However, the spectral data of the synthesized aaptoline A were not consistent with those of previous studies. The structure of the synthesized aaptoline A was confirmed by combined 2D NMR analysis. Additional studies on the bioactivity of the synthesized aaptoline A revealed that it has the ability to protect dopaminergic neurons against MPP⁺-induced neurotoxicity in C. elegans. In addition, impaired food-sensing ability and travel distance capability in C. elegans were significantly ameliorated by aaptoline A treatment, suggesting that aaptoline A can protect dopaminergic neurons both morphologically and functionally.

Modifications of amino acids using arenediazonium salts

Aryl transfer reactions from arenediazonium salts have started to make their impact in chemical biology with initial forays in the arena of arylative modifications and bio-conjugations of amino acids, peptides and proteins.

A concise formation of N-substituted 3,4-diarylpyrroles – synthesis and cytotoxic activity

Sequential condensation of a phenacyl halide with a primary amine and a phenylacetaldehyde led to N-substituted 3,4-diarylpyrroles. Synthesis of analogs of the marine alkaloid halitulin and cytotoxic studies are reported.