Scalable and Divergent Total Synthesis of (+)-Colletoic Acid, a Selective 11β-Hydroxysteroid Dehydrogenase Type 1 Inhibitor

Recent Progress in the Synthesis of Sesquiterpenoid Involving Spirocyclic Carbon Framework

Spirocarbocyclic natural products have been attracting considerable attention from synthetic organic chemists. This review focused on total syntheses of sesquiterpenoids involving spiro[4.5]decane and spiro[5.5]undecane scaffolds, compiling syntheses of colletoic acid, cubebol, axenol, vetispirene, hinesol, agarospirol, axenol, gleenol, exiguamide, exigurin, erythrodiene, spirojatamol, antroalbocin A, omphalic acid, dactylone, and aplydactonee since 2015.

Asymmetric Total Syntheses of (+)-5-epi-Schisansphenin B and the Proposed Structure of (+)-15-Hydroxyacora-4(14),8-diene

The asymmetric total syntheses of (+)-5-epi-schisansphenin B and the proposed structure of (+)-15-hydroxyacora-4(14),8-diene have been accomplished from 1,3-cyclopentadione (10) in eight synthetic steps. The enantioselective palladium-catalyzed redox-relay Heck alkenylation, the intramolecular Stetter reaction, and the regioselective Tiffeneau-Demjanov-type ring expansion were the pivotal steps in these syntheses.

Discovery and Characterization of 1H-1,2,3-Triazole Derivatives as Novel Prostanoid EP4 Receptor Antagonists for Cancer Immunotherapy

The prostanoid EP4 receptor is one of the key receptors associated with inflammatory mediator PGE₂-elicited immunosuppression in the tumor microenvironment. Blockade of EP4 signaling to enhance immunity-mediated tumor elimination has recently emerged as a promising strategy for cancer immunotherapy. In our efforts to discover novel subtype-selective EP4 antagonists, we designed and synthesized a class of 1H-1,2,3-triazole-based ligands that display low nanomolar antagonism activity toward the human EP4 receptor and excellent subtype selectivity. The most promising compound 59 exhibits single-digit nanomolar potency in the EP4 calcium flux and cAMP-response element reporter assays and effectively suppresses the expression of multiple immunosuppression-related genes in macrophage cells. On the basis of its favorable ADMET properties, compound 59 was chosen for further in vivo biological evaluation. Oral administration of compound 59 significantly inhibited tumor growth in the mouse CT26 colon carcinoma model accompanied by enhanced infiltration of cytotoxic T lymphocytes in the tumor tissue.

Mechanistic Insight on the Mode of Action of Colletoic Acid

The natural product colletoic acid (CA) is a selective inhibitor of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which primarily converts cortisone to the active glucocorticoid (GC) cortisol. Here, CA's mode of action and its potential as a chemical tool to study intracellular GC signaling in adipogenesis are disclosed. 11β-HSD1 biochemical studies of CA indicated that its functional groups at C-1, C-4, and C-9 were important for enzymatic activity; an X-ray crystal structure of 11β-HSD1 bound to CA at 2.6 Å resolution revealed the nature of those interactions, namely, a close-fitting and favorable interactions between the constrained CA spirocycle and the catalytic triad of 11β-HSD1. Structure-activity relationship studies culminated in the development of a superior CA analogue with improved target engagement. Furthermore, we demonstrate that CA selectively inhibits preadipocyte differentiation through 11β-HSD1 inhibition, suppressing other relevant key drivers of adipogenesis (i.e., PPARγ, PGC-1α), presumably by negatively modulating the glucocorticoid signaling pathway. The combined findings provide an in-depth evaluation of the mode of action of CA and its potential as a tool compound to study adipose tissue and its implications in metabolic syndrome.

Synthesis of selective 11β-HSD1 inhibitors based on dammarane scaffold

Inspired by natural 11β-HSD1 inhibitors hupehenols A - E, a ring-focused strategy was applied for the synthesis of 35 structurally diverse dammarane-type derivatives. These derivatives were effectively prepared from protopanaxadiol based on the modification of rings A and D. Among these compounds, ten were identified as selective 11β-HSD1 inhibitors (IC50 range: 101-1047 nM, SI range: 8-169) which exhibited inhibitory activities against human or mouse 11β-HSD1. Otherwise, we found 23a could selectively inhibit both human and mouse 11β-HSD1 with IC50 value of 994 and 213 nM (SI > 10 and > 47), respectively. Additionally, the molecular modelling results of 23a docking into the human and mouse 11β-HSD1 were in good agreement with the results from the enzyme inhibitory experiment. Moreover, valuable structural-activity relationship (SAR) information of dammarane-type 11β-HSD1 inhibitor was summarized.

Applications of oxazolidinones as chiral auxiliaries in the asymmetric alkylation reaction applied to total synthesis

In this review, a number of applications of chiral oxazolidinones in the asymmetric alkylation reaction applied to total synthesis are described.

Total syntheses of natural products containing spirocarbocycles

The spiro motif is becoming an increasingly prevalent structure in medicinal and organic chemistry. The total syntheses of natural products containing all-carbon spirocycles is reviewed.