A general and convenient synthesis of novel phosphotyrosine mimetics

Potent, Selective Agonists for the Cannabinoid-like Orphan G Protein-Coupled Receptor GPR18: A Promising Drug Target for Cancer and Immunity

The human orphan G protein-coupled receptor GPR18, activated by Δ9-tetrahydrocannabinol (THC), constitutes a promising drug target in immunology and cancer. However, studies on GPR18 are hampered by the lack of suitable tool compounds. In the present study, potent and selective GPR18 agonists were developed showing low nanomolar potency at human and mouse GPR18, determined in β-arrestin recruitment assays. Structure-activity relationships were analyzed, and selectivity versus cannabinoid (CB) and CB-like receptors was assessed. Compound 51 (PSB-KK1415, EC50 19.1 nM) was the most potent GPR18 agonist showing at least 25-fold selectivity versus CB receptors. The most selective GPR18 agonist 50 (PSB-KK1445, EC50 45.4 nM) displayed >200-fold selectivity versus both CB receptor subtypes, GPR55, and GPR183. The new GPR18 agonists showed minimal species differences, while THC acted as a weak partial agonist at the mouse receptor. The newly discovered compounds represent the most potent and selective GPR18 agonists reported to date.

Design and synthesis of cinnamic acid triptolide ester derivatives as potent antitumor agents and their biological evaluation

A series of novel cinnamic acid triptolide ester derivatives were synthesized, and their growth inhibitory properties against human hepatoma HepG2 cells were assessed as the measure of cytotoxicity with triptolide as the positive control. One of the phenolic hydroxyl phosphorylated products, CL20 was found to possess the best cytotoxicity and surpassed the parent natural triptolide, suggesting that compound CL20 is a promising antitumor lead compound and deserves further research of pharmacological activity. In addition, the structure-activity relationship for these compounds was also investigated.

Recent advances in synthetic and medicinal chemistry of phosphotyrosine and phosphonate-based phosphotyrosine analogues

Phosphotyrosine-containing compounds attract significant attention due to their potential to modulate signalling pathways by binding to phospho-writers, erasers and readers such as SH2 and PTB domain containing proteins. Phosphotyrosine derivatives provide useful chemical tools to study protein phosphorylation/dephosphorylation, and as such represent attractive starting points for the development of binding ligands and chemical probes to study biology, and for inhibitor and degrader drug design. To overcome enzymatic lability of the phosphate group, physiologically stable phosphonate-based phosphotyrosine analogues find utility in a wide range of applications. This review covers advances over the last decade in the design of phosphotyrosine and its phosphonate-based derivatives, highlights the improved and expanded synthetic toolbox, and illustrates applications in medicinal chemistry.

Atherton-Todd reaction: mechanism, scope and applications

Initially, the Atherton-Todd (AT) reaction was applied for the synthesis of phosphoramidates by reacting dialkyl phosphite with a primary amine in the presence of carbon tetrachloride. These reaction conditions were subsequently modified with the aim to optimize them and the reaction was extended to different nucleophiles. The mechanism of this reaction led to controversial reports over the past years and is adequately discussed. We also present the scope of the AT reaction. Finally, we investigate the AT reaction by means of exemplary applications, which mainly concern three topics. First, we discuss the activation of a phenol group as a phosphate which allows for subsequent transformations such as cross coupling and reduction. Next, we examine the AT reaction applied to produce fire retardant compounds. In the last section, we investigate the use of the AT reaction for the production of compounds employed for biological applications. The selected examples to illustrate the applications of the Atherton-Todd reaction mainly cover the past 15 years.

Solid-phase synthesis of Stat3 inhibitors incorporating O-carbamoylserine and O-carbamoylthreonine as glutamine mimics

O-Carbamoylserine and O-carbamoylthreonine are glutamine analogues that were incorporated into a Stat3 inhibitory peptide to probe the requirements of Gln at the pY+3 position. Fmoc-Ser-NHBn and Fmoc-Thr-NHBn were converted to nitrophenyl carbonates and were attached to Rink resin via a side-chain carbamate linkage. After assembly of the peptide, acid treatment resulted in O-carbamoylserine and O-carbamoylthreonine-containing peptides. The order of affinity for Stat3 was Gln > Ser(CONH2) >> Thr(CONH2) suggesting a relatively tight binding pocket for the side chain of glutamine.

Structure-activity relationships of the peptide deformylase inhibitor BB-3497: modification of the metal binding group

A series of analogues of the potent peptide deformylase (PDF) inhibitor BB-3497 containing alternative metal binding groups was synthesised. Enzyme inhibition and antibacterial activity data for these compounds revealed that the bidentate hydroxamic acid and N-formyl hydroxylamine structural motifs represent the optimum chelating groups on the pseudopeptidic BB-3497 backbone.

Design and synthesis of a pyridone-based phosphotyrosine mimetic

A novel pyridone-based tyrosine analog, 6, has been designed to mimic the binding interaction of SH2 domains with phosphotyrosine (pTyr) containing peptides. Synthesis of 6 features a key Pd catalyzed coupling of beta-iodoalanine with phosphonomethyl 4-pyridone triflate.