Li-Xin Gao

Cembrane diterpenoids from the soft coral Sarcophyton trocheliophorum Marenzeller as a new class of PTP1B inhibitors.

A detailed investigation of the South China Sea soft coral Sarcophyton trocheliophorum Marenzeller yielded, along with six known terpenes (6-11), the new sarcophytonolides N-R (1-5), whose structures have been elucidated by detailed spectroscopic analysis. Sarcophytonolides N-R are mono- or bicyclic cembranoids characterized by the presence of three/four double bonds and oxidized methyl groups. Some of the isolated compounds showed significant inhibitory activity against human protein tyrosine phosphatase 1B (PTP1B) enzyme, a key target for the treatment of type-II diabetes and obesity, and some preliminary structure-activity relationships have been drawn. This is the first report on the anti-PTP1B activity of cembrane diterpenoids.

4-Quinolone-3-carboxylic acids as cell-permeable inhibitors of protein tyrosine phosphatase 1B

Protein tyrosine phosphatase 1B is a negative regulator in the insulin and leptin signaling pathways, and has emerged as an attractive target for the treatment of type 2 diabetes and obesity. However, the essential pharmacophore of charged phosphotyrosine or its mimetic confer low selectivity and poor cell permeability. Starting from our previously reported aryl diketoacid-based PTP1B inhibitors, a drug-like scaffold of 4-quinolone-3-carboxylic acid was introduced for the first time as a novel surrogate of phosphotyrosine. An optimal combination of hydrophobic groups installed at C-6, N-1 and C-3 positions of the quinolone motif afforded potent PTP1B inhibitors with low micromolar IC50 values. These 4-quinolone-3-carboxylate based PTP1B inhibitors displayed a 2-10 fold selectivity over a panel of PTPs. Furthermore, the bidentate inhibitors of 4-quinolone-3-carboxylic acids conjugated with aryl diketoacid or salicylic acid were cell permeable and enhanced insulin signaling in CHO/hIR cells. The kinetic studies and molecular modeling suggest that the 4-quinolone-3-carboxylates act as competitive inhibitors by binding to the PTP1B active site in the WPD loop closed conformation. Taken together, our study shows that the 4-quinolone-3-carboxylic acid derivatives exhibit improved pharmacological properties over previously described PTB1B inhibitors and warrant further preclinical studies.

A novel class of small-molecule caspase-3 inhibitors prepared by multicomponent reactions

A series of tetra- and pentasubstituted polyfunctional dihydropyrroles 5 and 6 were synthesized via practical multicomponent reactions (MCRs) for research on their structure-activity relationship as caspase-3 inhibitors. Among 39 compounds evaluated, 14 of them exhibited inhibition against caspase-3 with IC(50) ranging from 5 to 20 μM. The inhibitory activities of 5 and 6 depend on the nature of substituents on different positions. 5 and 6 possess a different scaffold from those previously reported and are the first caspase-3 inhibitors prepared via MCRs. The most active compounds 5k (IC(50) = 5.27 μM) could therefore be used as a lead for the development of highly potent caspase-3 inhibitors as drug candidates for therapeutic agents by taking advantage of MCRs.

Divergent Synthesis of Multisubstituted Tetrahydrofurans and Pyrrolidines via Intramolecular Aldol-type Trapping of Onium Ylide Intermediates.

This paper reports a divergent strategy for the synthesis of multisubstituted tetrahydrofurans and pyrrolidines, starting from easily accessible β-hydroxyketones or β-aminoketones to react with diazo compounds. Under Rh(II) catalysis, this transformation is proposed to proceed through a metal-carbene-induced oxonium ylide or ammonium ylide formation followed by an intramolecular aldol-type trapping of these active intermediates. A series of highly substituted tetrahydrofurans and pyrrolidines are synthesized in high yields with good to excellent diastereoselectivities. Preliminary biological evaluations revealed that both types of heterocycles show good PTP1B inhibitory activities.

Click to a focused library of benzyl 6-triazolo(hydroxy)benzoic glucosides: novel construction of PTP1B inhibitors on a sugar scaffold.

With an aim of developing novel protein tyrosine phosphatase (PTP) 1B inhibitors based on sugar scaffolds, a focused library of benzyl 6-triazolo(hydroxy)benzoic glucosides was efficiently constructed via the modular and selective Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddtion (click chemistry). These glycoconjugates bearing alkyl chain length-varied bridges between the sugar and (hydroxy)-benzoic moieties were identified as new PTP1B inhibitors with selectivity over T-Cell PTP (TCPTP), SH2-Containing PTP-1 (SHP-1), SHP-2 and Leukocyte Antigen-Related Tyrosine Phosphatase (LAR). Molecular docking study sequentially elaborated the plausible binding modes of the structurally diverse sugar-based inhibitors with PTP1B.

Design and synthesis of paracaseolide A analogues as selective protein tyrosine phosphatase 1B inhibitors

A series of structurally related analogues of the natural product paracaseolide A were synthesized and identified as potent PTP1B inhibitors. Among these analogues, compound 10 in particular showed improved PTP1B enzyme inhibitory activity, high selectivity for PTP1B over TC-PTP, and improved cellular effects.

Chlorabietols A-C, Phloroglucinol-Diterpene Adducts from the Chloranthaceae Plant Chloranthus oldhamii.

Three unprecedented phloroglucinol-diterpene adducts, chlorabietols A-C (1-3), were isolated from the roots of the rare Chloranthaceae plant Chloranthus oldhamii. They represent a new class of compounds, featuring an abietane-type diterpenoid coupled with different alkenyl phloroglucinol units by forming a 2,3-dihydrofuran ring. Their structures were elucidated by detailed spectroscopic analysis, molecular modeling studies, and electronic circular dichroism calculations. Compounds 1-3 showed inhibitory activity against protein tyrosine phosphatase 1B (PTP1B) with IC50 values of 12.6, 5.3, and 4.9 μM, respectively.

Design, synthesis and in vitro activity of phidianidine B derivatives as novel PTP1B inhibitors with specific selectivity.

A series of phidianidine B derivatives were synthesized by introducing various heterocyclic rings. Their inhibitory effects on PTP1B and other PTPs (TCPTP, SHP1, SHP2 and LAR) were evaluated. A majority of them displayed significant inhibitory potency and specific selectivity over PTP1B. The SAR and molecular docking analysis were also described.

Diels–Alder adducts with PTP1B inhibition from Morus notabilis

Eight Diels-Alder adducts, morbilisins A-H (1-8), a known analogue, chalcomoracin (9), together with eleven known flavonoids and 2-arylbenzofurans, were isolated from the leaves of Morus notabilis. Their structures were elucidated by extensive spectroscopic analysis, including 1D, 2D NMR, MS, and ECD data. Compounds 1, 5, and 7-9 showed inhibition against PTP1B phosphatase activity in vitro.

Two Enantiomeric Pairs of Meroterpenoids from Rhododendron capitatum.

Two enantiomeric pairs of meroterpenoids, (-)- and (+)-rhodonoids A (1a and 1b) and B (2a and 2b), were isolated unprecedentedly from partially racemic mixtures that naturally occurred in Rhododendron capitatum. Their structures were fully determined by spectroscopic data, X-ray crystallography, and electronic circular dichroism analysis. Compounds 1a and 1b are the first examples of meromonoterpenes featuring a unique 6/6/6/4 ring system. Compounds 2a and 2b showed PTP1B inhibitory activity.