Optimization of Cyclic Peptide Property Using Chromatographic Capacity Factor on Permeability of Passive Cell Membrane and Human Induced Pluripotent Stem Cell-Derived Intestinal Membrane.

Cyclic peptides have attracted increasing attention as a privileged class of molecules addressing undruggable targets. Cell permeability of cyclic peptides has remained a challenging issue owing to their molecular properties. Various efficiency metrics have emerged to assess this issue. Among them, the lipophilic permeability efficiency (LPE) metric is the difference between an experimental 1,9-decadiene-water partition coefficient at pH 7.4 (log Ddec/w) and calculated octanol/water partition coefficients (ALogP). This metric provides insight into how structural changes affect permeability. Here, we demonstrate the chromatographic capacity factor (log k') of cyclic peptides using reversed-phase liquid chromatography as an alternative to log Ddec/w, which enables efficient and reliable experimental lipophilicity for the adoption of LPE in early drug discovery. The log k' indicates the passive membrane permeability of cyclic peptides and can be used to optimize passive membrane permeability in combination with other parameters. In addition, intestinal membrane permeability of cyclic peptides on human induced pluripotent stem cell-derived intestinal epithelial cells was achieved with log k' and high passive membrane permeability, although cyclic peptides are P-glycoprotein substrates. These approaches could facilitate optimization of properties of cyclic peptides for oral administration and contribute to the successful discovery and development of cyclic peptides.

Discovery of 2-Sulfinyl-Diazabicyclooctane Derivatives, Potential Oral ß-Lactamase Inhibitors for Infections Caused by Serine ß-Lactamase-Producing Enterobacterales.

Coadministration of ß-lactam and ß-lactamase inhibitor (BLI) is one of the well-established therapeutic measures for bacterial infections caused by ß-lactam-resistant Gram-negative bacteria, whereas we have only two options for orally active BLI, clavulanic acid and sulbactam. Furthermore, these BLIs are losing their clinical usefulness because of the spread of new ß-lactamases, including extended-spectrum ß-lactamases (ESBLs) belonging to class A ß-lactamases, class C and D ß-lactamases, and carbapenemases, which are hardly or not inhibited by these classical BLIs. From the viewpoints of medical cost and burden of healthcare personnel, oral therapy offers many advantages. In our search for novel diazabicyclooctane (DBO) BLIs possessing a thio-functional group at the C2 position, we discovered a 2-sulfinyl-DBO derivative (2), which restores the antibacterial activities of an orally available third-generation cephalosporin, ceftibuten (CTB), against various serine ß-lactamase-producing strains including carbapenem-resistant Enterobacteriaceae (CRE). It can be orally absorbed via the ester prodrug modification and exhibits in vivo efficacy in a combination with CTB.

Introduction of a Thio Functional Group to Diazabicyclooctane: An Effective Modification to Potentiate the Activity of ß-Lactams against Gram-Negative Bacteria Producing Class A, C, and D Serine ß-Lactamases.

By the emergence and worldwide spread of multi-drug-resistant Gram-negative bacteria, there have been growing demands for efficacious drugs to cure these resistant infections. The key mechanism for resistance to ß-lactam antibiotics is the production of ß-lactamases, which hydrolyze and deactivate ß-lactams. Diazabicyclooctane (DBO) analogs play an important role as one of the new classes of ß-lactamase inhibitors (BLIs), and several compounds such as avibactam (AVI) have been approved by the FDA, along with many derivatives under clinical or preclinical development. Although these compounds have a similar amide substituent at the C2 position, we have recently reported the synthesis of novel DBO analogs which possess a thio functional group. This structural modification enhances the ability to restore the antimicrobial activities of cefixime (CMF) against pathogens producing classes A, C, and D serine ß-lactamases compared with AVI and expands the structural tolerance at the six position. Furthermore, some of these analogs showed intrinsic microbial activities based on multipenicillin binding protein (PBP) inhibition. This is the unique feature which has never been observed in DBOs. One of our DBOs had a pharmacokinetic profile comparable to that of other DBOs. These results indicate that the introduction of a thio functional group into DBO is a novel and effective modification to discover a clinically useful new BLI.

Synthesis of 2-Thio-Substituted 1,6-Diazabicyclo[3.2.1]octane Derivatives, Potent ß-Lactamase Inhibitors.

Approval of avibactam by the FDA has led to the recognition of 1,6-diazabicyclo[3.2.1]octane (DBO) derivatives as attractive compounds for ß-lactamase inhibition. We achieved a concise and collective synthesis of 2-thio-substituted DBO derivatives. The synthesis involves diastereoselective photo-induced Barton decarboxylative thiolation, which can be applied to large-scale synthesis. The DBO analogues exhibited strong inhibitory activities against serine ß-lactamases and acceptable solution stabilities for clinical development.

Pharmacological evaluation of novel (6-aminopyridin-3-yl)(4-(pyridin-2-yl)piperazin-1-yl) methanone derivatives as TRPV4 antagonists for the treatment of pain.

A novel series of (6-aminopyridin-3-yl)(4-(pyridin-2-yl)piperazin-1-yl) methanone derivatives were identified as selective transient receptor potential vanilloid 4 (TRPV4) channel antagonist and showed analgesic effect in Freund's Complete Adjuvant (FCA) induced mechanical hyperalgesia model in guinea pig and rat. Modification of right part based on the compound 16d which was disclosed in our previous communication led to the identification of compound 26i as a flagship compound. In this paper, we described the details about design, synthesis and structure-activity relationship (SAR) analysis at right and left part of these derivatives (Fig. 1).

Discovery of novel 2',4'-dimethyl-[4,5'-bithiazol]-2-yl amino derivatives as orally bioavailable TRPV4 antagonists for the treatment of pain: Part 2.

A series of 2',4'-dimethyl-[4,5'-bithiazol]-2-yl amino derivatives have been identified as selective TRPV4 antagonists that display inhibition potencies against 4α-phorbol 12,13-didecanoate (4αPDD), well known as a TRPV4 selective agonist and/or a hypotonicity. In particular, 9-(6-((2',4'-dimethyl-[4,5'-bithiazol]-2-yl)amino)nicotinoyl)-3-oxa-9-azabicyclo[3.3.1]nonan-7-one showed an analgesic effect in Freund's Complete Adjuvant (FCA) induced mechanical hyperalgesia model in guinea pig (reported in Part 1). However, there are some concerns such as species differences and the need for higher plasma exposure to achieve target efficacy for evaluation by an in vivo pain model. In this Letter, we report the resolution of some of the problems by further optimizing the chemical scaffold.

Perfluoroalkyl Grignard Reagents: NMR Study of 1-Heptafluoropropylmagnesium Chloride in Solution.

We report on the generation of a perfluoroalkyl Grignard reagent ((F)RMgX) by exchange reaction between a perfluoroalkyl iodide ((F)R-I) and a Grignard reagent (RMgX). (19)F NMR was applied to monitor the generation of n-C3F7MgCl. Additional NMR techniques, including (19)F COSY, NOESY, and pulsed gradient spin-echo (PGSE) diffusion NMR, were invoked to assign peaks observed in (19)F spectrum. Schlenk equilibrium was observed and was significantly influenced by solvent, diethyl ether, or THF.

Chemo-, regio-, and stereo-selective perfluoroalkylations by a Grignard complex with zirconocene.

The synthesis of highly reactive perfluoroalkyl Grignard reagents with early transition metal zirconocene complexes and their new types of highly chemo-, regio-, and stereo-selective perfluoroalkylation reactions are reported with epoxides in particular. The zirconocene complex is advantageous in activating the perfluoroalkyl Grignard species. The zirconocene·Grignard complexes were clarified by DOSY. Both (1)H and (19)F DOSY analyses show that the addition of MAO and dioxane to the mixture of RFMgCl and Cp2ZrCl2 connects Cp2Zr and RFMg to generate the zirconocene/perfluoroalkyl-Grignard/dioxane complex.

Paradigm shift from alkaline (earth) metals to early transition metals in fluoroorganometal chemistry: perfluoroalkyl titanocene(III) reagents prepared via not titanocene(II) but titanocene(III) species.

Perfluoroalkyl (RF) titanocene reagents [Cp2Ti(III)RF] synthesized via [Cp2Ti(III)Cl] rather than [Cp2Ti(II)] show new types of perfluoroalkylation reactions. The [Cp2Ti(III)RF] reagents exhibit a wide variety of reactivity with carbonyl compounds including esters and nitriles, and selectivities far higher than those reported for conventional RFLi and RFMgX reagents.

Cu-catalyzed trifluoromethylation of aryl iodides with trifluoromethylzinc reagent prepared in situ from trifluoromethyl iodide.

The trifluoromethylation of aryl iodides catalyzed by copper(I) salt with trifluoromethylzinc reagent prepared in situ from trifluoromethyl iodide and Zn dust was accomplished. The catalytic reactions proceeded under mild reaction conditions, providing the corresponding aromatic trifluoromethylated products in moderate to high yields. The advantage of this method is that additives such as metal fluoride (MF), which are indispensable to activate silyl groups for transmetallation in the corresponding reactions catalyzed by copper salt by using the Ruppert-Prakash reagents (CF3SiR3), are not required.