From citronellal to iridoids: asymmetric synthesis of iridoids and their analogues via organocatalytic intramolecular Michael reactions.

A series of iridoids, including iridomyrmecin A, B, C', D', (-)-isoiridomyrmecin, (+)-7-epi-boschnialactone, and the inside-yohimbine analogues have been synthesized from readily available, naturally occurring (-)-citronellal via the key step reaction of metathesis, organocatalysis, and subsequent transformations, such as reduction, lactonization, alkylation, Pictet-Spengler reaction and lactamization. Notably, the use of DBU as an additive in the organocatalytic intramolecular Michael reaction of an aldehyde ester with Jørgensen-Hayashi catalysts resulted in better stereoselectivity than the conditions using acetic acid as an additive. The structures of three products have been unequivocally established with single-crystal X-ray crystallographic analyses.

The azatryptophan-based fluorescent platform for in vitro rapid screening of inhibitors disrupting IKKß-NEMO interaction.

The nuclear factor-κB (NF-κB) plays an important role in inflammatory and immune responses. Aberrant NF-κB signaling is implicated in multiple disorders, including cancer. Targeting the regulatory scaffold subunit IκB kinase γ (IKKγ/NEMO) as therapeutic interventions could be promising due to its specific involvement in canonical NF-κB activation without interfering with non-canonical signaling. In this study, the use of unnatural amino acid substituted IKKß with unique photophysical activity to sense water environment changes upon interaction with NEMO provides a powerful in vitro screening platform that would greatly facilitate the identification of compounds having the potential to disrupt IKKß-NEMO interaction, and thus specifically modulate the canonical NF-κB pathway. We then utilized a competitive binding platform to screen the binding ability of a number of potential molecules being synthesized. Our results suggest that a lead compound (-)-PDC-099 is a potent agent with ascertained potency to disrupt IKKß-NEMO complex for modulating NF-κB canonical pathway.

Asymmetric Synthesis of Spirocyclopentane Oxindoles Containing Four Consecutive Stereocenters and Quaternary α-Nitro Esters via Organocatalytic Enantioselective Michael-Michael Cascade Reactions.

An enantioselective domino Michael-Michael reaction of nitroolefins and 2-nitro-3-arylacrylates has been established, which provided a series of spirocyclopentane oxindoles with four consecutive stereocenters including quaternary α-nitro esters with good yields (up to 73%) and excellent enantioselectivities (up to 97% ee). The reaction was realized and optimized with the aid of a chiral squaramide-amine catalyst. The structures of 11 products were confirmed by single-crystal X-ray diffraction analysis.

Organocatalytic Enantioselective Michael-Michael-Michael-Aldol Condensation Reactions: Control of Six Stereocenters in a Quadruple-Cascade Asymmetric Synthesis of Polysubstituted Spirocyclic Oxindoles.

An organocatalyzed enantioselective Michael-Michael-Michael-aldol cascade reaction for the construction of cyclopentane fused spirooxindoles was achieved. The domino reaction provided the spirooxindoles with six contiguous stereocenters including a quaternary center in good yields (55-64%) with excellent enantioselectivities (up to >99% ee). Enantioselective Michael-Michael-Michael-aldol condensation-aromatization reactions of an isomeric product were observed.