Biosynthesis of Menaquinone in E.†coli: Identification of an Elusive Isomer of SEPHCHC.

In the biosynthesis of menaquinone in bacteria, the thiamine diphosphate-dependent enzyme MenD catalyzes the decarboxylative carboligation of α-ketoglutarate and isochorismate to (1R,2S,5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxycyclohex-3-ene-1-carboxylate (SEPHCHC). The regioisomer of SEPHCHC, namely (1R,5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxycyclohex-2-ene-1-carboxylate (iso-SEPHCHC), has been considered as a possible product, however, its existence has been doubtful due to a spontaneous elimination of pyruvate from SEPHCHC to 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC). In this work, the regioisomer iso-SEPHCHC was distinguished from SEPHCHC by liquid chromatography-tandem mass spectrometry. Iso-SEPHCHC was purified and identified by NMR spectroscopy. Just as SEPHCHC remained hidden as a MenD product for more than two decades, its regioisomer iso-SEPHCHC has remained until now.

Alteration of the Route to Menaquinone towards Isochorismate-Derived Metabolites.

Chorismate and isochorismate constitute branch-point intermediates in the biosynthesis of many aromatic metabolites in microorganisms and plants. To obtain unnatural compounds, we modified the route to menaquinone in Escherichia coli. We propose a model for the binding of isochorismate to the active site of MenD ((1R,2S, 5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxycyclohex-3-ene-1-carboxylate (SEPHCHC) synthase) that explains the outcome of the native reaction with α-ketoglutarate. We have rationally designed variants of MenD for the conversion of several isochorismate analogues. The double-variant Asn117Arg-Leu478Thr preferentially converts (5S,6S)-5,6-dihydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHD), the hydrolysis product of isochorismate, with a >70-fold higher ratio than that for the wild type. The single-variant Arg107Ile uses (5S,6S)-6-amino-5-hydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHA) as substrate with >6-fold conversion compared to wild-type MenD. The novel compounds have been made accessible in vivo (up to 5.3 g L-1 ). Unexpectedly, as the identified residues such as Arg107 are highly conserved (>94 %), some of the designed variations can be found in wild-type SEPHCHC synthases from other bacteria (Arg107Lys, 0.3 %). This raises the question for the possible natural occurrence of as yet unexplored branches of the shikimate pathway.

Method validation and preliminary pharmacokinetic studies on the new designer stimulant 3-fluorophenmetrazine (3-FPM).

Pharmaceutical research not only provides the basis for the development of new medicinal products but also for the synthesis of new drugs of abuse. 3-Fluorophenmetrazine (3-FPM), a fluorinated derivative of the anorectic phenmetrazine, was first patented in 2011 and appeared on the drug market in 2014. Though invented for potential medical purposes, pharmacokinetic data on this compound, crucial for interpreting forensic as well as clinical cases, are not available. Therefore, a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method for the detection of 3-FPM in serum, urine, and oral fluid was developed, validated for urine and serum, and used to quantify 3-FPM in samples obtained during a controlled self-experiment. The method proved to be linear, selective and sufficiently sensitive. The limits of detection (LODs) were 0.1 ng/mL, 0.2 ng/mL, and 0.05 ng/mL in serum, urine, and oral fluid. Inter-day precision and intra-day precision (RSD) in serum samples were below 6.3% and below 8.5%, respectively. The highest serum concentration (cmax ) of 210 ng/mL was reached 2.5 hours (tmax ) after ingestion. The elimination half-life and the volume of distribution were calculated to be approx. 8.8 hours and 400 L (5.3 L/kg). 3-FPM could be detected in serum and urine up to 82 hours and 116 hours, respectively. It was still detected in the last oral fluid sample taken 55 hours after ingestion. 3-FPM was mainly excreted unchanged. Main metabolic reactions were aryl-hydroxylation and N-hydroxylation. Interestingly, the product of oxidative ring opening (2-amino-1-(3-fluorophenyl)propan-1-ol) showed the largest window of detection in the self-experiment.

5F-Cumyl-PINACA in 'e-liquids' for electronic cigarettes: comprehensive characterization of a new type of synthetic cannabinoid in a trendy product including investigations on the in vitro and in vivo phase I metabolism of 5F-Cumyl-PINACA and its non-fluorinated analog Cumyl-PINACA.

PURPOSE: In recent years e-liquids used in electronic cigarettes have become an attractive alternative to smoking tobacco. A new trend is the use of e-liquids containing synthetic cannabinoids (SCs) instead of smoking cannabis or herbal mixtures laced with SCs. In the frame of a systematic monitoring of the online market of 'legal high' products, e-liquids from online retailers who also sell herbal blends were bought. METHODS: The products were analyzed by gas chromatography-mass spectrometry. In some of the e-liquids an unknown compound was detected which was identified as the SC 5F-Cumyl-PINACA (1-(5-fluoropentyl)-N-(2-phenylpropan-2-yl)-1H-indazole-3-carboxamide) by nuclear magnetic resonance analysis. To investigate the phase I metabolism of this new class of compounds, 5F-Cumyl-PINACA and its non-fluorinated analog Cumyl-PINACA were incubated with pooled human liver microsomes (pHLM). Cumyl-PINACA was additionally ingested orally (0.6 mg) by a volunteer in a controlled self-experiment. To assess the relative potency of Cumyl-PINACA a set of SCs were characterized using a cAMP assay. RESULTS: Metabolism of 5F-Cumyl-PINACA and Cumyl-PINACA showed similarities with AM-2201 and JWH-018. The main metabolites were formed by hydroxylation at the N-pentyl side chain. The main metabolites detected in the volunteer's urine sample were the same as in the pHLM assay. All SCs tested with the cAMP assay were full agonists at the CB1 receptor. Cumyl-PINACA was the most potent SC among the tested compounds and showed an EC50 value of 0.06 nM. CONCLUSIONS: The increasing popularity of e-liquids particularly among young people, and the extreme potency of the added SCs, pose a serious threat to public health. To our knowledge, this is the first report describing the tentative identification of human in vivo metabolites of Cumyl-PINACA and 5F-Cumyl-PINACA.

Characterization and in vitro phase I microsomal metabolism of designer benzodiazepines: An update comprising flunitrazolam, norflurazepam, and 4'-chlorodiazepam (Ro5-4864).

The number of newly appearing benzodiazepine derivatives on the new psychoactive substances (NPS) drug market has increased over the last couple of years totaling 23 'designer benzodiazepines' monitored at the end of 2017 by the European Monitoring Centre for Drugs and Drug Addiction. In the present study, three benzodiazepines [flunitrazolam, norflurazepam, and 4'-chlorodiazepam (Ro5-4864)] offered as 'research chemicals' on the Internet were characterized and their main in vitro phase I metabolites tentatively identified after incubation with pooled human liver microsomes. For all compounds, the structural formula declared by the vendor was confirmed by gas chromatography-mass spectrometry (GC-MS), liquid chromatography-tandem mass spectrometry (LC MS/MS), liquid chromatography-quadrupole time of flight-mass spectrometry (LC-QTOF-MS) analysis and nuclear magnetic resonance (NMR) spectroscopy. The metabolic steps of flunitrazolam were monohydroxylation, dihydroxylation, and reduction of the nitro function. The detected in vitro phase I metabolites of norflurazepam were hydroxynorflurazepam and dihydroxynorflurazepam. 4'-Chlorodiazepam biotransformation consisted of N-dealkylation and hydroxylation. It has to be noted that 4'-chlorodiazepam and its metabolites show almost identical LC-MS/MS fragmentation patterns to diclazepam and its metabolites (delorazepam, lormetazepam, and lorazepam), making a sufficient chromatographic separation inevitable. Sale of norflurazepam, the metabolite of the prescribed benzodiazepines flurazepam and fludiazepam, presents the risk of incorrect interpretation of analytical findings.

Structural characterization and pharmacological evaluation of the new synthetic cannabinoid CUMYL-PEGACLONE.

The number of new psychoactive substances (NPS) that have emerged on the European market has been rapidly growing in recent years, with a particularly high number of new compounds from the group of synthetic cannabinoid receptor agonists. There have been various political efforts to control the trade and the use of NPS worldwide. In Germany, the Act to control the distribution of new psychoactive substances (NpSG) came into force in November 2016. In this new act, two groups of substances were defined, the group "cannabimimetics/synthetic cannabinoids" covering indole, indazole, and benzimidazole core structures, and a second group named "compounds derived from 2-phenethylamine." Shortly after, the first retailers of "herbal blends" promoted new products allegedly not violating the German NpSG. We describe the identification and structural elucidation of one of the first synthetic cannabinoids not being covered by the NpSG, 5-pentyl-2-(2-phenylpropan-2-yl)-2,5-dihydro-1H-pyrido[4,3-b]indol-1-one. For isolation of the substance a flash chromatography separation was applied. The structure elucidation was performed using gas chromatography-mass spectrometry (GC-MS), gas chromatography-solid state infrared spectroscopy (GC-sIR), liquid chromatography-electrospray ionization-quadrupole time of flight-mass spectrometry (LC-ESI-qToF-MS) and nuclear magnetic resonance (NMR) analysis. Additionally, binding affinity towards the cannabinoid receptors CB1 and CB2 and efficacy in a cAMP accumulation assay were measured, showing full agonistic activity and high potency at both receptors. The new compound bears a γ-carboline core structure circumventing the German NpSG and the generic definitions in other national laws. As a semi-systematic name for 2-cumyl-5-pentyl-gamma-carbolin-1-one CUMYL-PEGACLONE is suggested.

Wide Distribution of Foxicin Biosynthetic Gene Clusters in Streptomyces Strains - An Unusual Secondary Metabolite with Various Properties.

Streptomyces diastatochromogenes Tü6028 is known to produce the polyketide antibiotic polyketomycin. The deletion of the pokOIV oxygenase gene led to a non-polyketomycin-producing mutant. Instead, novel compounds were produced by the mutant, which have not been detected before in the wild type strain. Four different compounds were identified and named foxicins A-D. Foxicin A was isolated and its structure was elucidated as an unusual nitrogen-containing quinone derivative using various spectroscopic methods. Through genome mining, the foxicin biosynthetic gene cluster was identified in the draft genome sequence of S. diastatochromogenes. The cluster spans 57 kb and encodes three PKS type I modules, one NRPS module and 41 additional enzymes. A foxBII gene-inactivated mutant of S. diastatochromogenes Tü6028 ΔpokOIV is unable to produce foxicins. Homologous fox biosynthetic gene clusters were found in more than 20 additional Streptomyces strains, overall in about 2.6% of all sequenced Streptomyces genomes. However, the production of foxicin-like compounds in these strains has never been described indicating that the clusters are expressed at a very low level or are silent under fermentation conditions. Foxicin A acts as a siderophore through interacting with ferric ions. Furthermore, it is a weak inhibitor of the Escherichia coli aerobic respiratory chain and shows moderate antibiotic activity. The wide distribution of the cluster and the various properties of the compound indicate a major role of foxicins in Streptomyces strains.

Characterization and in vitro phase I microsomal metabolism of designer benzodiazepines - an update comprising adinazolam, cloniprazepam, fonazepam, 3-hydroxyphenazepam, metizolam and nitrazolam.

Designer benzodiazepines represent an emerging class of new psychoactive substances. While other classes of new psychoactive substances such as cannabinoid receptor agonists and designer stimulants are mainly consumed for hedonistic reasons, designer benzodiazepines may also be consumed as 'self-medication' by persons suffering from anxiety or other psychiatric disorders or as stand-by 'antidote' by users of stimulant and hallucinogenic drugs. In the present study, five benzodiazepines (adinazolam, cloniprazepam, fonazepam, 3-hydroxyphenazepam and nitrazolam) and one thienodiazepine (metizolam) offered as 'research chemicals' on the Internet were characterized and their main in vitro phase I metabolites tentatively identified after incubation with pooled human liver microsomes. For all compounds, the structural formula declared by the vendor was confirmed by nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry (MS), liquid chromatography MS/MS and liquid chromatography quadrupole time-of-flight MS analysis. The detected in vitro phase I metabolites of adinazolam were N-desmethyladinazolam and N-didesmethyladinazolam. Metizolam showed a similar metabolism to other thienodiazepines comprising monohydroxylations and dihydroxylation. Cloniprazepam was metabolized to numerous metabolites with the main metabolic steps being N-dealkylation, hydroxylation and reduction of the nitro function. It has to be noted that clonazepam is a metabolite of cloniprazepam, which may lead to difficulties when interpreting analytical findings. Nitrazolam and fonazepam both underwent monohydroxylation and reduction of the nitro function. In the case of 3-OH-phenazepam, no in vitro phase I metabolites were detected. Formation of licensed benzodiazepines (clonazepam after uptake of cloniprazepam) and the sale of metabolites of prescribed benzodiazepines (fonazepam, identical to norflunitrazepam, and 3-hydroxyphenazepam) present the risk of incorrect interpretation of analytical findings. Copyright © 2016 John Wiley & Sons, Ltd.

Separation and structural characterization of the new synthetic cannabinoid JWH-018 cyclohexyl methyl derivative "NE-CHMIMO" using flash chromatography, GC-MS, IR and NMR spectroscopy.

Synthetic cannabinoids have become an integral part of the drugs of abuse market since many years. The most frequent form of consumption for this class of substances is smoking of herbal mixtures purchased via the Internet. In this article the identification and structure elucidation of a new synthetic cannabinoid, [1-(cyclohexylmethyl)-1H-indol-3-yl](naphthalen-1-yl)methanone, is described. The compound was found along with 5F-ADB in a 'herbal mixture' called 'Jamaican Gold Extreme', which was sent to our laboratory in the context of a suspected intoxication. For isolation of the substance a flash chromatography separation was applied. Structure elucidation was performed using gas chromatography-mass spectrometry (GC-MS), gas chromatography solid-state infrared (GC-sIR) and nuclear magnetic resonance (NMR) analysis. The new compound can be described as the cyclohexyl methyl derivative of the first generation synthetic cannabinoid JWH-018, and the authors suggest to use "NE-CHMIMO" as a semisystematic name.

Characterization of the designer benzodiazepine diclazepam and preliminary data on its metabolism and pharmacokinetics.

Designer benzodiazepines, first offered in online shops selling 'research chemicals' in 2012, provide an attractive alternative to prescription-only benzodiazepines as they are readily available over the Internet at a low price. However, as data regarding pharmacokinetic parameters, metabolism, and detectability in biological fluids are limited, they present a challenge for forensic laboratories. Most recently, diclazepam (other names: 2-chlorodiazepam, Ro 5-3448 or 7-chloro-5-(2-chlorophenyl)-1-methyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one) emerged as a new compound in this class of drugs. In this paper, this new designer benzodiazepine was characterized utilizing nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS) as well as liquid chromatography tandem mass spectrometry (LC-MS/MS) techniques. Furthermore, a self-experiment was performed to gain preliminary data on pharmacokinetic properties and to identify the main metabolites. For this purpose, one tablet of diclazepam (declared amount: 1 mg) was ingested by one of the authors, and serum as well as urine samples were collected for 14 and 21 days, respectively. Based on this study, diclazepam has an approximate elimination half-life of 42 h and is metabolized into the pharmacologically active benzodiazepines delorazepam, lorazepam, and lormetazepam which can be detected in urine for 6, 19, and 11 days, respectively, when applying the presented LC-MS/MS method. In serum, the consumption could be proven between 99 h post-intake targeting the parent compound and up to 10 days targeting the metabolite delorazepam. As immunochemical assays are applied for screening purposes quite often, detectability using this technique was assessed, especially since detection of low-dosed benzodiazepines can be sometimes problematic. However, only one of the utilized immunochemical assays was capable of detecting the intake of one tablet diclazepam, and the positive results were restricted to a few urine samples showing relatively high creatinine concentrations.

Identification and structural characterization of the synthetic cannabinoid 3-(1-adamantoyl)-1-pentylindole as an additive in 'herbal incense'.

Since the end of 2010, more than 20 synthetic cannabimimetics have been identified in 'Spice' products, demonstrating the enormous dynamic in this field. In an effort to cope with the problem, many countries have already undertaken legal measures by putting some of these compounds under control. Nevertheless, once a number of compounds were scheduled, they were soon replaced by other synthetic cannabinoids. In this article, we report the identification of a new--and due to its substitution pattern rather uncommon--cannabimimetic found in several 'herbal incense' products. The GC-EI mass spectrum first led to misidentification as the alpha-methyl-derivative of JWH-250. However, since both substances show different retention indices, thin-layer chromatography was used to isolate the unknown compound. After application of nuclear magnetic resonance spectroscopy, high-resolution MS and GC-MS/MS techniques, the compound was identified as 3-(1-adamantoyl)-1-pentylindole, a derivative of JWH-018 carrying an adamantoyl moiety instead of a naphthoyl group. This finding supports that the listing of synthetic cannabinoids as prohibited substances triggers the appearance of compounds with uncommon substituents. Moreover, it emphasizes the necessity of being aware of the risk of misidentification when using techniques sometimes providing only limited structural information like GC-MS.

Functions of genes and enzymes involved in phenalinolactone biosynthesis.

Phenalinolactones are novel terpene glycoside antibiotics produced by Streptomyces sp. Tü6071. Inactivation of three oxygenase genes (plaO2, plaO3 and plaO5), two dehydrogenase genes (plaU, plaZ) and one putative acetyltransferase gene (plaV) led to the production of novel phenalinolactone derivatives (PL HS6, PL HS7, PL HS2 and PL X1). Furthermore, the exact biosynthetic functions of two enzymes were determined, and their in vitro activities were demonstrated. PlaO1, an Fe(II)/alpha-ketoglutarate-dependent dioxygenase, is responsible for the key step in gamma-butyrolactone formation, whereas PlaO5, a cytochrome P450-dependent monooxygenase, catalyses the 1-C-hydroxylation of phenalinolactone D. In addition, stable isotope feeding experiments with biosynthetic precursors shed light on the origin of the carbons in the gamma-butyrolactone moiety.

The tert-butyl group in chemistry and biology.

The unique reactivity pattern elicited by the crowded tert-butyl group is highlighted by summarising characteristic applications. Starting from the use of this simple hydrocarbon moiety in chemical transformations, via its relevance in Nature and its implication in biosynthetic and biodegradation pathways, the way through to its possible application in biocatalytic processes is described.

Bicyclic glutamic acid derivatives.

For the second-generation asymmetric synthesis of the trans-tris(homoglutamic) acids via Strecker reaction of chiral ketimines, the cyanide addition as the key stereodifferentiating step produces mixtures of diastereomeric alpha-amino nitrile esters the composition of which is independent of the reaction temperature and the type of the solvent, respectively. The subsequent hydrolysis is exclusively achieved with concentrated H(2)SO(4) yielding diastereomeric mixtures of three secondary alpha-amino alpha-carbamoyl-gamma-esters and two diastereomeric cis-fused angular alpha-carbamoyl gamma-lactams as bicyclic glutamic acid derivatives, gained from in situ stereomer differentiating cyclisation of the secondary cis-alpha-amino alpha-carbamoyl-gamma-esters. Separation was achieved by CC. The pure secondary trans-alpha-amino alpha-carbamoyl-gamma-esters cyclise on heating and treatment with concentrated H(2)SO(4), respectively, to diastereomeric cis-fused angular secondary alpha-amino imides. Their hydrogenolysis led to the enantiomeric cis-fused angular primary alpha-amino imides. The configuration of all compounds was completely established by NMR methods, CD-spectra, and by X-ray analyses of the (alphaR,1R,5R)-1-carbamoyl-2-(1-phenylethyl)-2-azabicyclo[3.3.0]octan-3-one and of the trans-alphaS,1S,2R-2-ethoxycarbonylmethyl-1-(1-phenylethylamino)cyclopentanecarboxamide.

Rigid nonproteinogenic cyclic amino acids as ligands for glutamate receptors: trans-tris(homoglutamic) acids.

The second-generation asymmetric synthesis of the trans-tris(homoglutamic) acids reported herein proceeds via Strecker reaction of chiral ketimines, obtained from condensation of racemic 2-ethoxycarbonylmethylcyclopentanone and commercially available (S)- and (R)-1-phenylethylamine, respectively. In the key stereodifferentiating step, the cyanide addition leads to mixtures of diastereomeric alpha-amino nitrile-esters, the composition of which is independent of the reaction temperature and the type of the solvent, respectively. Hydrolysis of the alpha-amino nitrile-esters with concentrated H(2)SO(4) yielded diastereomeric mixtures of secondary alpha-amino amido-esters, which after separation were hydrogenolyzed and hydrolyzed each to the enantiomeric trans-1-amino-2-carboxymethylcyclopentanecarboxylic acids. Their configuration was completely established by NMR methods, CD spectra, and X-ray analysis of the trans-1S,2R-configured secondary alpha-amino amido-ester. In receptor binding assays and functional tests, trans-1S,2R-1-amino-2-carboxymethylcyclopentanecarboxylic acid hydrochloride was found to behave as a selective mGluR(2)-antagonist without relevant binding properties at iGluRs.

Syntheses and GABA uptake properties of 6-ether- and 6-enol ether-substituted nipecotic acids.

6-aralkylether- and 6-arylenol-ether-substituted nipecotic acids were synthesized. These analogues are poor GABA uptake inhibitors. The electronegative region concept developed in the N-substituted nipecotic acid series cannot be transferred on the side chain of this series of 6-substituted analogues.