Highly diastereoselective synthesis of new, carbostyril-based type of conformationally-constrained β-phenylserines

Analogues of natural products yaequinolones as potential inflammatory inhibitors: Design, synthesis and biological evaluation

Inflammation is connected with a variety of diseases and there is still a need to develop more effective and safer anti-inflammatory drugs. Herein, we synthesized, resolved, and characterized eight enantiopure isomers of yaequinolone J1 (1), yaequinolone J2 (2), 4'-desmethoxyyaequinolone J1 (3), and 4'-desmethoxyyaequinolone J2 (4). The key synthetic steps were extended and 34 racemic analogues modified at the 4-aryl, the N-position, and the pyran ring were designed and synthesized. All the synthesized compounds were evaluated for their anti-inflammatory activities in RAW 264.7 cells of which 13 compounds showed significant inhibition of nitric oxide (NO) production at a concentration of 0.1 μM, which was more potent than that of indomethacin. Furthermore, compounds (-)-3, (-)-4, 5h, and 6g reduced the production of IL-6 in LPS-stimulated RAW 264.7 cells at a concentration of 50 nM. A preliminary SAR indicated that 3'-Br (5h), 4'-NO₂ (6g) on 4-phenyl and 3-bromobenzyl (7f) on the N-position were the most effective substituents. This is the first report of the anti-inflammatory yaequinolone alkaloids and the present study provided evidence for exploiting this series of highly efficacious derivatives for new anti-inflammatory agents.

Scalable total synthesis of (+)-aniduquinolone A and its acid-catalyzed rearrangement to aflaquinolones

The strong antibacterial, antiviral and anticancer activities demonstrated by quinolones make them promising lead structures and important synthetic targets for drug discovery. Here, we report, to the best of our knowledge, the first scalable total synthesis of antiviral (+)-aniduquinolone A, possessing a 3,4-dioxygenated 5-hydroxy-4-aryl-quinolin-2(1H)-one skeleton. This synthetic strategy explores E-stereoselective Horner-Wadsworth-Emmons (HWE) olefination as the key step to assemble isopropenyl substituted tetrahydrofuran onto the 3,4-dioxygenated 5-hydroxy-4-aryl-quinolin-2(1H)-one core, which is built by highly diastereoselective intramolecular aldol reaction. Moreover, two sets of stereoisomers of aniduquinolone A with substantially overlapping NMR data were synthesized completely and assigned unambiguously by comprehensive analysis of both their spectroscopic and X-ray diffraction data. Unexpectedly, aflaquinolones A, C, and D that feature different 2,4-dimethyl cyclohexanone moieties were transformed successfully from (+)-aniduquinolone A by treating with TFA. The methodology delineated herein can be applied broadly to the synthesis of natural alkaloids containing the core structure of 3,4-dioxygenated 5-hydroxy-4-aryl-quinolin-2(1H)-one.

Five-Step Synthesis of Yaequinolones J1 and J2

A concise synthesis of yaequinolones J1 and J2 is reported. The route is based on the aryne insertion into the σ-C-N bond of an unsymmetric imide followed by a diastereoselective aldol cyclization of the resulting N-acylated aminobenzophenone. The chromene motif is generated in the first step by an organocatalytic tandem Knoevenagel electrocyclization of citral and 2-bromoresorcinol. The approach adheres to the ideality principle, using almost exclusively strategic bond-forming reactions.

Synthesis of Quinolinone Alkaloids via Aryne Insertions into Unsymmetric Imides in Flow

A general strategy for the synthesis of 3,4-dioxygenated quinolin-2-one natural products is reported. The key step is a regioselective insertion of arynes into unsymmetric imides. When performed in continuous flow, the reaction proceeds within minutes, while lower yields and longer reaction times are observed in batch. The resulting N-acylated 2-aminobenzophenones were transformed to (±)-peniprequinolone, (±)-aflaquinolones E and F, (±)-6-deoxyaflaquinolone E, (±)-quinolinones A and B, and (±)-aniduquinolone C in 1-3 steps.

Total Synthesis and Absolute Stereochemical Assignment of the Insecticidal Metabolites Yaequinolones J1 and J2

A highly stereocontrolled total synthesis of (-)-yaequinolone J1 and (+)-yaequinolone J2 was accomplished using an Evans auxiliary to establish a syn-diol unit in an acyclic appendage to a preformed benzopyran core bearing a homoprenyl group. The first total synthesis of a complex member of this family of 3,4-dioxygenated 3,4-dihydro 4-aryl quinolin-2-(1 H)-ones also allowed the assignment of absolute stereochemistry, thereby suggesting the same for several members of this family of biogenetically related alkaloids hitherto reported with relative configurations of stereogenic carbons for some and absolute assignments relying on empirical data for others.

Efficient total synthesis of neocryptolepine and synthetic access to 6-methylquinindoline from a common intermediate

The total synthesis of neocryptolepine and the synthesis of its non-natural isomer 6-methyl quinindoline were efficiently achieved in a few steps from a common intermediate.

A convenient approach to an advanced intermediate toward the naturally occurring, bioactive 6-substituted 5-hydroxy-4-aryl-1H-quinolin-2-ones

An advanced intermediate for the total synthesis of the 5-hydroxy-4-aryl-3,4-dihydro-1H-quinolin-2-one natural products and a 3,4-bisdesoxy analog of peniprequinolone were synthesized.

The 3,4-dioxygenated 5-hydroxy-4-aryl-quinolin-2(1H)-one alkaloids. Results of 20 years of research, uncovering a new family of natural products

The title alkaloids are discussed. Emphasis is placed on their isolation, source microorganisms and structure, as well as relevant biological activities and synthetic progress.