New Route to the Synthesis of the Isocryptolepine Alkaloid and Its Related Skeletons Using a Modified Pictet–Spengler Reaction

Abstract

A new route to the synthesis of the isocryptolepine alkaloid with antimalarial activity using a modified Pictet-Spengler reaction has been devised. The strategy was then used to generate libraries based on three structural variants of the alkaloid. Compounds based on these three variants in general were accessed in three steps through a modified PictetSpengler cyclization reaction as the key step. The C-2-, C-3-, or N-1-linked (aminoaryl)indoles (8, 12, 13) required for cyclization were obtained by treating the corresponding indoles with o-halonitrobenzene using either nucleophilic re-

Synthesis and antifungal activities of novel 5,6-dihydro-indolo[1,2-a]quinoxaline derivatives

“…Although Kundu and coauthors have reported the synthesis of indolo [1,2-a]quinoxalines in situ via the intermediates, 5,6-dihydro-indolo[1,2-a]quinoxalines, excess amounts (1.5 equiv.) of trifluoroacetic acid (TFA), a strong Brønsted acid, were required to prepare 5,6-dihydro-indolo[1,2-a]quinoxalines by the PicteteSpengler reaction [23]. Consequently, the development of environmentally friendly and less expensive catalysts for the construction of a library of 5,6-dihydro-indolo[1,2-a]quinoxalines is very important.…”

Cross‐Coupling of Heteroarenes by CH Functionalization: Recent Progress towards Direct Arylation and Heteroarylation Reactions Involving Heteroarenes Containing One Heteroatom

“…of o-iodonitrobenzene in dioxane at 100 8C using K 2 CO 3 as the base (Scheme 124). [162] As shown in Scheme 124, compounds 232a-c were then used as precursors to 7H-indoloA C H T U N G T R E N N U N G [2,3-c]quinolines 233. [162] In 2010, a versatile catalyst system based on PdA C H T U N G T R E N N U N G (OAc) 2 /bis(diphenylphosphino)methane (dppm) that works "on water" giving site selective arylation of free NH-indoles with aryl halides was developed by Djakovitch and co-workers.…”

“…[162] As shown in Scheme 124, compounds 232a-c were then used as precursors to 7H-indoloA C H T U N G T R E N N U N G [2,3-c]quinolines 233. [162] In 2010, a versatile catalyst system based on PdA C H T U N G T R E N N U N G (OAc) 2 /bis(diphenylphosphino)methane (dppm) that works "on water" giving site selective arylation of free NH-indoles with aryl halides was developed by Djakovitch and co-workers. [163] The control of the site-selectivity was achieved by small changes in the base/halide partners so that both C-2 and C-3 arylylated 1H-indoles could be obtained.…”

Compromise between compactness of micelle and overlap integral toward Förster resonance energy transfer from an indoloquinoline derivative to fluorescein: A fluorometric study

“…They show wide applications as anti-malarial [2], anti-microbial [4,5], anti-imflammatory [6], and anticancer agents [7]. Cryptolepines are also known to bind tightly to DNA and behave as typical intercalating agents [8][9][10]. Considerable interest has been shown to the anti-plasmodial indoloquinolines and attempts have been made to synthesize similar isomers to compare their biological activities with the naturally occurring isomers [11].…”