Asymmetric Synthesis of Chiral Dihydrothiopyrans via an Organocatalytic Enantioselective Formal Thio [3 + 3] Cycloaddition Reaction with Binucleophilic Bisketone Thioethers

Base-Promoted Reaction of 4-Chloro-3-vinyl Coumarins, Phenacylpyridinium Bromides, and Elemental Sulfur: A Designed Approach to Thiopyrano[4,3-c]chromen-5(1H)-ones

A designed synthesis of thiopyrano[4,3-c]chromen-5(1H)-ones was developed based on a base-promoted three-component reaction between 4-chloro-3-vinyl coumarins, phenacylpyridinium bromides, and elemental sulfur. Readily available starting materials, mild conditions, chemoselectivity, operational simplicity, and synthetically useful yields are some highlighted advantages of these transformations.

Magnesium catalyzed [3 + 3] heteroannulation of α-enolic dithioesters with MBH acetate: access to functionalized 3,4-dihydro-2H-thiopyrans

Magnesium catalysis proved to be efficient towards [3 + 3] chemo- and diastereoselective heteroannulation employing racemic Morita-Baylis-Hillman (MBH) acetate as the C3 unit and α-enolic dithioester as the C2S1 unit, leading to highly substituted 3,4-dihydro-2H-thiopyrans in excellent yields. The compatibility with a wide range of functional groups makes this domino formation of C-C and C-S bonds interesting. DFT analyses for the regioselective formation of the intermediate was performed.

Discovery of novel KRAS‒PDEδ inhibitors with potent activity in patient-derived human pancreatic tumor xenograft models

KRAS‒PDEδ interaction is revealed as a promising target for suppressing the function of mutant KRAS. The bottleneck in clinical development of PDEδ inhibitors is the poor antitumor activity of known chemotypes. Here, we identified novel spiro-cyclic PDEδ inhibitors with potent antitumor activity both in vitro and in vivo. In particular, compound 36l (K _D = 127 ± 16 nmol/L) effectively bound to PDEδ and interfered with KRAS-PDEδ interaction. It influenced the distribution of KRAS in Mia PaCa-2 cells, downregulated the phosphorylation of t-ERK and t-AKT and promoted apoptosis of the cells. The novel inhibitor 36l exhibited significant in vivo antitumor potency in pancreatic cancer patient-derived xenograft (PDX) models. It represents a promising lead compound for investigating the druggability of KRAS‒PDEδ interaction.

Organocatalytic asymmetric synthesis of highly functionalized spiro-thiazolone–cyclopropane-oxindoles bearing two vicinal spiro quaternary centers

Spiro-thiazolone–cyclopropane-oxindoles with three contiguous stereocenters, including two vicinal quaternary centers, were obtained via an organocatalytic asymmetric Michael/alkylation cascade reaction.

l-Phenylalanine potassium catalyzed asymmetric formal [3 + 3] annulation of 2-enoyl-pyridine N-oxides with acetone

A highly enantioselective formal [3 + 3] annulation of 2-enoyl-pyridine N-oxides with acetone was developed.

Synthesis of spiro-tetrahydrothiopyran-oxindoles by Michael–aldol cascade reactions: discovery of potential P53-MDM2 inhibitors with good antitumor activity

Novel one-pot Michael–aldol cascade reactions were used to efficiently construct spiro-tetrahydrothiopyran-oxindoles with good in vitro antitumor activity.

Total Syntheses of (±)-Rhodonoids C, D, E, F, and G and Ranhuadujuanine B

Here we describe the divergent, biosynthetically inspired syntheses of (±)-rhodonoids C-G and (±)-ranhuadujuanine B. The key steps of the syntheses include the construction of the chromene unit through a formal oxa-[3 + 3] annulation and a biomimetic acid-catalyzed ring cyclization. Cationic [2 + 2] cycloaddition is accomplished to form the cyclobutane core of (±)-rhodonoids E and F.

Total Syntheses of (±)-Rhodonoids A and B and C12-epi-Rhodonoid B

Total syntheses of (±)-rhodonoids A and B and C12-epi-rhodonoid B are described here. A unified strategy employed in these syntheses is an intramolecular oxa-[3 + 3] annulation for accessing the chromene unit. A Fe(OTf)₃-promoted diastereoselective cationic [2 + 2] cycloaddition and a photochemical [2 + 2] cycloaddition were featured to construct the cyclobutane core of (±)-rhodonoids A and B and C12-epi-rhodonoid B, respectively. Fe(OTf)₃ also leads to an interesting bridged tetracycle, which was unambiguously confirmed by single crystal X-ray analysis.

The first organocatalytic, ortho-regioselective inverse-electron-demand hetero-Diels–Alder reaction

The development of the unprecedented ortho-regioselective inverse-electron-demand hetero-Diels–Alder (IEDHDA) reaction is described.

Enantioselective organocatalytic Michael addition of isorhodanines to α,β-unsaturated aldehydes

The Michael reaction of substituted isorhodanines with α,β-unsaturated aldehydes in the presence of a catalytic amount of a chiral secondary amine is presented. This transformation proceeds in good to high yields furnishing the corresponding 4,5-disubstituted isorhodanine adducts in good to excellent enantioselectivities.

Meeting Organocatalysis with Drug Discovery: Asymmetric Synthesis of 3,3'-Spirooxindoles Fused with Tetrahydrothiopyrans as Novel p53-MDM2 Inhibitors

An organocatalytic enantioselective Michael-Michael cascade reaction is developed for the synthesis of chiral spirotetrahydrothiopyrans. This highly functionalized scaffold was assembled in moderate to good yield (55-74%) and excellent diastereo- and enantioselectivities (>30:1 dr, ≥ 99% ee) with the creation of four consecutive stereogenic centers. The novel spiro-oxindole scaffold is validated as a new class of p53-MDM2 protein-protein interaction inhibitors with good antitumor activity.

Asymmetric α,γ-Regioselective [3 + 3] Formal Cycloadditions of α,β-Unsaturated Aldehydes via Cascade Dienamine-Dienamine Catalysis

Asymmetric α,γ-regioselective [3 + 3] formal cycloadditions of α,β-unsaturated aldehydes and 2-nitroallylic acetates have been developed for the first time. These reactions proceeded through a domino Michael addition-Michael addition sequence via an unusual cascade dienamine-dienamine catalysis of a chiral secondary amine, and multifunctional cyclohexene derivatives were generally constructed in moderate yields with excellent stereoselectivity after simple treatment with K2CO3.

A highly enantioselective, organocatalytic [3+2]-cycloannulation reaction towards the de novo-synthesis of 1-cyclopentenyl-α-keto esters

A novel [3+2]-cycloannulation process produces cyclopentenes with good yields and excellent enantioselectivity via a domino-vinylogous Michael–Knoevenagel reaction.