An acid-promoted pseudocine substitution manifold of γ-aminocyclopentenone enables divergent access to polycyclic indole derivatives

Synthesis of Etrasimod (APD334): Al2O3-Promoted Decarboxylative Rearrangements of Cyclopentenones with Stereochemical Inversion

This study presents an efficient synthesis pathway for etrasimod, starting from (+)-cis-4-acetoxy-2-cyclopenten-1-ol, yielding 5.6% overall with 98% enantiomeric excess. The crucial intermediate, (4R)-anilinocyclopent-2-enone, was derived from the (S)-alcohol/isocyanate adduct through a concerted, Al2O3-promoted decarboxylative rearrangement, which inverted the configuration. A tetracyclic fused lactam was formed via a one-pot acylation-Michael addition, followed by keto α-arylation. Subsequent removal of the oxo group facilitated the synthesis of cyclopenta[b]indol-3-ylacetic acid through a series of reactions, including methanolysis, indoline oxidation, and hydrolysis.

Hydrogen bonding-promoted tunable approach for access to aza-bicyclo-[3.3.0]octanes and cyclopenta[b] pyrroles

A unified strategy is disclosed that builds on successfully engaging the aniline nitrogen of 1,3-amphoteric γ-aminocyclopentenone for a tandem annulation with electron-poor alkynes, solely assisted by the H-bonding network of HFIP. This metal-free mild strategy provides access to medicinally relevant aza-bicyclo-octanes en route to another important scaffold: cyclopenta[b]pyrrole.

Rapid Access to Densely Functionalized Cyclopentenyl Sulfoximines through a Sc-Catalyzed Aza-Piancatelli Reaction

Sulfoximines make up a class of compounds of growing interest for crop science and medicinal chemistry, but methods for directly incorporating them into complex molecular scaffolds are lacking. Here we report a scandium-catalyzed variant of the aza-Piancatelli cyclization that can directly incorporate sulfoximines as nucleophiles rather than the classical aniline substrates. Starting from 2-furylcarbinols and sulfoximines, the reaction provides direct access to 4-sulfoximinocyclopentenones, a new scaffold bearing cyclopentenone and sulfoximine motifs, both of interest for bioactive compounds.

Furan ring opening reaction for the synthesis of 2,5-dicarbonyl-3-ene-phosphates

Furan ring opening reactions are essential in organic synthesis, enabling the incorporation of diverse functional groups and the construction of complex molecular structures. A highly efficient and practical method for synthesizing 2,5-dicarbonyl-3-ene-phosphates from readily available biomass furan and dialkyl phosphonates is reported. The reaction, catalyzed by FeCl3, demonstrated wide substrate scope and high synthetic efficiency. Gram-scale synthesis was achieved, and a one-pot reaction provided a quick access route to the desired compounds. Additionally, a successful Diels-Alder reaction highlighted the versatility of the methodology.

Access to densely functionalized spirocyclopentenonyl oxindole frameworks via aza- and carbo-Piancatelli rearrangement

A new strategy for access to spirocyclopentenonyl oxindole frameworks is disclosed. Suitably anchored furfuryl alcohol at C3 of an oxindole was used for the aza-Piancatelli rearrangement, which furnished spirocyclic aminocyclopentenone frameworks with catalytic phosphomolybdic acid. The scope of the transformation was extended to the carbo-Piancatelli rearrangement with various indole derivatives.