Synthesis and antitumor activity of fused quinoline derivatives. III. Novel N-glycosylamino-indolo[3,2-b]quinolines

Indium-Catalyzed Annulation of o-Acylanilines with Alkoxyheteroarenes: Synthesis of Heteroaryl[b]quinolines and Subsequent Transformation to Cryptolepine Derivatives

We disclose herein the first synthetic method that is capable of offering heteroaryl[b]quinolines (HA[b]Qs) with structural diversity, which include tricyclic and tetracyclic structures with (benzo)thienyl, (benzo)furanyl, and indolyl rings. The target HA[b]Q is addressed by the annulation of o-acylanilines and MeO–heteroarenes with the aid of an indium Lewis acid that effectively works to make two different types of the N–C and C–C bonds in one batch. A series of indolo[3,2-b]quinolines prepared here can be subsequently transformed to structurally unprecedented cryptolepine derivatives. Mechanistic studies showed that the N–C bond formation is followed by the C–C bond formation. The indium-catalyzed annulation reaction thus starts with the nucleophilic attack of the NH₂ group of o-acylanilines to the MeO-connected carbon atom of the heteroaryl ring in an S_NAr fashion, and thereby the N–C bond is formed. The resulting intermediate then cyclizes to make the C–C bond through the nucleophilic attack of the heteroaryl-ring-based carbon atom to the carbonyl carbon atom, providing the HA[b]Q after aromatizing dehydration.

Probing the N-5 region of the indoloquinoline alkaloid, cryptolepine for anticryptococcal activity

N-5 Alkylated analogues of cryptolepine were synthesized and tested for anticryptococcal activity. Evidence provided in this study suggests that the active form of cryptolepine consists of the flat tetracyclic aromatic ring with the methyl group on the N-5 atom. It was also found that changes in the electronic density around the N-5 atom do not appear to affect activity. Steric hindrance of the N-5 substituents seems to decrease activity. Through systematic modification of the N-5 alkyl groups, o-phenylpentyl group was shown to possess the highest potency thus far.

Electrolytic Partial Fluorination of Organic Compounds. 31.(1) Regioselective Anodic Fluorination of 2-Quinolyl and 4-(7-Trifluoromethyl)quinolyl Sulfides and the Factors Affecting Its Optimization

Electrochemical fluorination of 2-quinolyl and 4-(7-trifluoromethyl)quinolyl sulfides bearing an electron-withdrawing group at the position alpha to the sulfur atom was studied. Fluorination was successfully carried out using Et(4)NF.nHF (n = 3, 4) and Et(3)N.3HF as a supporting electrolyte and a fluoride ion source in dimethoxyethane in a divided cell to provide the corresponding alpha-fluorinated sulfides in good yields. A trifluoromethyl group positioned on the quinoline ring significantly enhanced anodic alpha-fluorination. 4-(Methylthio)-7-(trifluoromethyl)quinoline was also found to undergo anodic fluorination efficiently. Solvent effects of various donor numbers were also established.