Peptide-to-Small Molecule: Discovery of Non-Covalent, Active-Site Inhibitors of β-Herpesvirus Proteases

Viral proteases, the key enzymes that regulate viral replication and assembly, are promising targets for antiviral drug discovery. Herpesvirus proteases are enzymes with no crystallographically confirmed noncovalent active-site binders, owing to their shallow and polar substrate-binding pockets. Here, we applied our previously reported "Peptide-to-Small Molecule" strategy to generate novel inhibitors of β-herpesvirus proteases. Rapid selection with a display technology was used to identify macrocyclic peptide 1 bound to the active site of human cytomegalovirus protease (HCMVPro) with high affinity, and pharmacophore queries were defined based on the results of subsequent intermolecular interaction analyses. Membrane-permeable small molecule 19, designed de novo according to this hypothesis, exhibited enzyme inhibitory activity (IC50 = 10-6 to 10-7 M) against β-herpesvirus proteases, and the design concept was proved by X-ray cocrystal analysis.

Discovery of S-217622, a Noncovalent Oral SARS-CoV-2 3CL Protease Inhibitor Clinical Candidate for Treating COVID-19

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in millions of deaths and threatens public health and safety. Despite the rapid global spread of COVID-19 vaccines, effective oral antiviral drugs are urgently needed. Here, we describe the discovery of S-217622, the first oral noncovalent, nonpeptidic SARS-CoV-2 3CL protease inhibitor clinical candidate. S-217622 was discovered via virtual screening followed by biological screening of an in-house compound library, and optimization of the hit compound using a structure-based drug design strategy. S-217622 exhibited antiviral activity in vitro against current outbreaking SARS-CoV-2 variants and showed favorable pharmacokinetic profiles in vivo for once-daily oral dosing. Furthermore, S-217622 dose-dependently inhibited intrapulmonary replication of SARS-CoV-2 in mice, indicating that this novel noncovalent inhibitor could be a potential oral agent for treating COVID-19.

Facile Chemoselective Strategy toward Capturing Sphingoid Bases by a Unique Glutaraldehyde-Functionalized Resin

Sphingoid bases, which have a 2-amino-1,3-diol common functional group, are the structural backbone units of all sphingolipids. Recently, much attention has been focused on sphingoid bases because of their potentially beneficial bioactivities toward various cancer cells as well as their dietary interest. However, low abundance and the handling complexity caused by their amphiphilic character led to very limited research on them. Glutaraldehyde has two aldehyde groups, and it reacts rapidly with the 2-amino-1,3-diol functional group of sphingosine to give a tricyclic product. Immobilization of glutaraldehyde on a resin was successfully performed by organic synthesis, starting from trans-p-coumaric acid via eight steps. This approach suppresses the self-polymerization of glutaraldehyde, and addition of water to the developed resin causes the formation of cyclic double hemiacetal function, which avoids oxidation like a reducing sugar in nature and makes it stable even for up to 1 year incubation. The resin was applied to the solid-phase extracting experiment of free sphingosine from human serum at a concentration of 280 nM. Another extraction study of edible golden oyster mushrooms showed that the sphingoid base was selectively captured from complex natural extracts. These results demonstrate that the developed glutaraldehyde resin method is a highly selective method, and hence, the combination of it with the o-phthaldialdehyde HPLC method was confirmed as an efficient and sensitive method for analysis of sphingoid bases in biological samples.

Juvenile play experience does not affect nicotine sensitization and voluntary consumption of nicotine in adult rats

Juvenile play experiences promote behavioral flexibility in rats. If other early positive experiences, such as tactile stimulation, are given prior to exposure to psychostimulants, the behavioral response to the drug is attenuated. The objective of the present study was to determine if the experience of juvenile play behavior would attenuate the response to nicotine. Two experiments were conducted: (1) behavioral sensitization to nicotine exposure, and (2) voluntary consumption of nicotine. For both experiments, rats were reared either with three same-sex peers (play group) or one adult (no play group) during their juvenile period. Then, as adults, half of each group was exposed to repeated injections of nicotine and the other half to saline. Prior play experience had no effect on behavioral sensitization or on voluntary consumption of nicotine. It remains to be determined whether juvenile experience with play influences the rewarding properties of nicotine in social contexts as adults.

Training on motor and visual spatial learning tasks in early adulthood produces large changes in dendritic organization of prefrontal cortex and nucleus accumbens in rats given nicotine prenatally

Experience-dependent plasticity is an ongoing process that can be observed and measured at multiple levels. The first goal of this study was to examine the effects of prenatal nicotine on the performance of rats in three behavioral tasks (elevated plus maze (EPM), Morris water task (MWT), and Whishaw tray reaching). The second goal of this experiment sought to examine changes in dendritic organization following exposure to the behavioral training paradigm and/or low doses of prenatal nicotine. Female Long-Evans rats were administered daily injections of nicotine for the duration of pregnancy and their pups underwent a regimen of behavioral training in early adulthood (EPM, MWT, and Whishaw tray reaching). All offspring exposed to nicotine prenatally exhibited substantial increases in anxiety. Male offspring also showed increased efficiency in the Whishaw tray-reaching task and performed differently than the other groups in the probe trial of the MWT. Using Golgi-Cox staining we examined the dendritic organization of the medial and orbital prefrontal cortex as well as the nucleus accumbens. Participation in the behavioral training paradigm was associated with dramatic reorganization of dendritic morphology and spine density in all brain regions examined. Although both treatments (behavior training and prenatal nicotine exposure) markedly altered dendritic organization, the effects of the behavioral experience were much larger than those of the prenatal drug exposure, and in some cases interacted with the drug effects.

A vibrational circular dichroism approach to the determination of the absolute configurations of flavorous 5-substituted-2(5H)-furanones

Sotolon (1) and maple furanone (2) are naturally occurring chiral furanones. These 5-substituted-2(5H)-furanones are industrially significant aroma compounds due to their characteristic organoleptic properties and extraordinarily low odor thresholds. Each enantiomer of 1 and 2 was successfully obtained by preparative enantioselective supercritical fluid chromatography. The absolute configuration of 1 was confirmed as (R)-(-)-1 and (S)-(+)-1 by adopting the vibrational circular dichroism (VCD) approach. The absolute configuration of 2, which has remained ambiguous since its discovery in 1957, was determined as (R)-(+)-2 and (S)-(-)-2 for the first time by the VCD technique. Surprisingly, the signs of the optical rotation of 2 are opposite of those of 1 regardless of their identical absolute configurations. This observation emphasizes the risk in absolute configurational assignments based on comparison of optical rotation signs of similar structures. Odor evaluation of the enantiomers of 2 revealed different odor intensities.

Stereochemical study of a novel tautomeric furanone, homofuraneol

A mixture of tautomers with unique keto-enol structures, 5-ethyl-4-hydroxy-2-methylfuran-3(2H)-one and 2-ethyl-4-hydroxy-5-methylfuran-3(2H)-one (EHMF, homofuraneol, 1a and 1b), comprises four structural isomers including their enantiomers. The four isomers were successfully separated by chromatographic optical resolution, and their odor evaluation was performed. Determination of the absolute chemistry of 1a and 1b were accomplished for the first time by direct measurement of the VCD spectra of their methyl ether derivatives 4a and 4b compared with the calculated ones as well as chemical relay reaction. The relationship between odor characteristics and stereochemistry was also examined.

Stereochemical studies of odorous 2-substituted-3(2H)-furanones by vibrational circular dichroism

Chiral naturally occurring aroma compounds often exhibit enantiomeric excesses due to their stereoselective biogenesis. In general, significant organoleptic differences are perceived between these enantiomers. Chiral 2-substituted-3(2H)-furanones, featuring a unique keto-enol tautomer, the cause of their racemization, have been known to play an important role in flavor because of their extremely low threshold values and their burnt sugar odor characteristics. Since the discovery of these important aroma chemicals, they have been used in large quantities as raw materials in the flavor and fragrance industry. However, absolute configurations of these furanone derivatives have remained ambiguous for the past 40 years. Here optical resolutions of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, 2,5-dimethyl-4-methoxy-3(2H)-furanone, and 4-acetoxy-2,5-dimethyl-3(2H)-furanone were accomplished using chiral CO(2) supercritical fluid chromatography (SFC). Their absolute configurations were unraveled for the first time using the vibrational circular dichroism (VCD) technique as well as by chemical relay reactions. Odor evaluation of each enantiomer revealed relationships between their configurations and odor activities.

Stereochemical studies of hexylitaconic acid, an inhibitor of p53-HDM2 interaction

Hexylitaconic acid (1) is an intriguing natural product possessing a chiral carbon, and both its enantiomers have been found in nature. Enantiomeric pure (+)-(1) and (-)-(1) were successfully prepared by racemic synthesis followed by enantiomeric separation in a chiral HPLC system. Their absolute configurations were clarified by the vibrational circular dichroism technique using their methyl esters 2 and lactones 3. Their inhibitory activities against the interaction of p53-HDM2 were also examined.

Stereochemical study of chiral tautomeric flavorous furanones by vibrational circular dichroism

2-Substituted-3(2H)-furanone derivatives are industrially significant aroma compounds possessing a unique keto-enol tautomeric feature causing their racemization. Absolute configurations of two flavorous furanones, which have remained unclear for the past 40 years since their discovery, were clarified by the vibrational circular dichroism technique as well as chemical relay reactions. Odor evaluation of each enantiomer revealed relationships between their configurations and their odor activities.

Stereochemical studies of sialic acid derivatives by vibrational circular dichroism

Systematic VCD studies of N-acetylneuraminic acid (Neu5Ac), a recognition-related unique carbohydrate, were performed for the first time. Two pairs of anomeric isomers regarding a quaternary C2 asymmetric carbon of Neu5Ac derivatives were synthesized. VCD spectral patterns around the ester carbonyl region, as well as other Mid-IR regions, would be practical markers to distinguish the C2 stereochemistry.

Effects of Central Metal Ions on Vibrational Circular Dichroism Spectra of Tris-(β-diketonato)metal(III) Complexes

Vibrational circular dichroism (VCD) spectra of a series of [M(III)(acac)3] (acac = acetylacetonato; M = Cr, Co, Ru, Rh, Ir, and Al) and [M(III)(acac)2(dbm)] (dbm = dibenzoylmethanato; M = Cr, Co, and Ru) have been investigated experimentally and/or theoretically in order to see the effect of the central metal ion on the vibrational dynamics of ligands. The optical antipodes give the mirror-imaged spectra in the region of 1700-1000 cm(-1). The remarkable effect of the central metal ion is observed experimentally on the VCD peaks due to C-O stretches (1500-1300 cm(-1)) for both [M(III)(acac)3] and [M(III)(acac)2(dbm)]. In the case of Delta-[M(III)(acac)3], for example, the order of frequency of two C-O stretches (E and A2 symmetries) is dependent on the kind of a central metal ion as follows: E (-) > A2 (+) for M = Co, Rh, and Ir, while A2 (+) > E (-) for M = Cr and Ru. In the case of Delta-[M(III)(acac)2(dbm)], the order of frequency of three C-O stretches (A, B, and B symmetries) is as follows: A (-) > B (+) > B (+) for Co(III), B (+) > A (-) > B (-) for Cr(III), and A (-) > B (+) > B (-) for Ru(III). These results imply that the energy levels of C-O stretches are delicately affected by the kind of central metal ion. Since such detailed information is not obtained from the IR spectra alone, the VCD spectrum can probe the effect of the central metal ion on interligand cooperative vibration modes.