Design, synthesis, and biological evaluation of new bis-benzylisoquinoline-based analogues as potential neuromuscular blocking agents.

Neuromuscular blocking agents (NMBAs) are widely used in anesthesia for intubation and surgical muscle relaxation. Novel atracurium and mivacurium derivatives were developed, with compounds 18c, 18d, and 29a showing mivacurium-like relaxation at 27.27 nmol/kg, and 15b, 15c, 15e, and 15h having a shorter duration at 272.7 nmol/kg. The structure-activity and configuration-activity relationships of these derivatives and 29a's binding to nicotinic acetylcholine receptors were analyzed through molecular docking. Rabbit trials showed 29a has a shorter duration compared to mivacurium. This suggests that linker properties, ammonium group substituents, and configuration are crucial for NMBA activity and duration, with compound 29a emerging as a potential ultra-short-acting NMBA.

Template-Directed Synthesis of Bivalent, Broad-Spectrum Hosts for Neuromuscular Blocking Agents.

We report on the synthesis of bivalent water-soluble calix[4]arene and calix[5]arene hosts, Super-sCx4 and Super-sCx5 as new broad-spectrum supramolecular binders of neuromuscular blocking agents (NMBAs). Synthesis was achieved using the target bisquaternary amine NMBAs as a template to link two highly anionic p-sulfonatocalixarene building blocks in aqueous solution. Bivalent anionic hosts Super-sCx4 and Super-sCx5 bind by engaging both quaternary amines present on a variety of NMBAs. We report low µM binding to structurally diverse alkyl, steroidal, curarine and benzylisoquinoline NMBAs with high selectivity over the neurotransmitter acetylcholine and a variety of other hydrophobic amines.

Synthetic Pinnatoxins A and G Reversibly Block Mouse Skeletal Neuromuscular Transmission In Vivo and In Vitro.

Pinnatoxins (PnTXs) A-H constitute an emerging family belonging to the cyclic imine group of phycotoxins. Interest has been focused on these fast-acting and highly-potent toxins because they are widely found in contaminated shellfish. Despite their highly complex molecular structure, PnTXs have been chemically synthetized and demonstrated to act on various nicotinic acetylcholine receptor (nAChR) subtypes. In the present work, PnTX-A, PnTX-G and analogue, obtained by chemical synthesis with a high degree of purity (>98%), have been studied in vivo and in vitro on adult mouse and isolated nerve-muscle preparations expressing the mature muscle-type (α1)2ß1δε nAChR. The results show that PnTX-A and G acted on the neuromuscular system of anesthetized mice and blocked the compound muscle action potential (CMAP) in a dose- and time-dependent manner, using a minimally invasive electrophysiological method. The CMAP block produced by both toxins in vivo was reversible within 6-8 h. PnTX-A and G, applied to isolated extensor digitorum longus nerve-muscle preparations, blocked reversibly isometric twitches evoked by nerve stimulation. The action of PnTX-A was reversed by 3,4-diaminopyridine. Both toxins exerted no direct action on muscle fibers, as revealed by direct muscle stimulation. PnTX-A and G blocked synaptic transmission at mouse neuromuscular junctions and PnTX-A amino ketone analogue (containing an open form of the imine ring) had no effect on neuromuscular transmission. These results indicate the importance of the cyclic imine for interacting with the adult mammalian muscle-type nAChR. Modeling and docking studies revealed molecular determinants responsible for the interaction of PnTXs with the muscle-type nAChR.

Isomeric Carborane Neuromuscular Blocking Agents.

We synthesized a family of neuromuscular blocking agents (NMB) based on decamethonium, but containing a carborane cluster in the methylene chain between the two quaternary ammonium groups. The carborane cluster isomers o-NMB, m-NMB, and p-NMB were tested in animals for neuromuscular block and compared with agents used clinically: rocuronium and decamethonium. All three isomers caused reversible muscle weakness in mice as determined by grip strength and inverted screen tests, with a potency rank of p-NMB > rocuronium > decamethonium > m-NMB > o-NMB. The mechanism of action of the compounds was determined by using the in vitro rat phrenic nerve hemi-diaphragm preparation and electrophysiologic measurements in cells. Neostigmine reversed hemi-diaphragm weakness caused by the three isomers and rocuronium, but not succinylcholine. In electrophysiologic recordings of currents through acetylcholine receptor channels, the carborane compounds did not activate channel activity but did inhibit channel activation by acetylcholine. These results demonstrate that the carborane neuromuscular blocking agents are non-depolarizers in contrast to the depolarizing action of the parent compound.

Recent Progress of Novel Steroid Derivatives and Their Potential Biological Properties.

Steroid and its derivatives have been proved to have important and diverse biological functions, which present the wide spectrum of biological activities such as antitumor, antiviral, antibacterial, antimicrobial, antifungal, antioxidant, insecticidal, aromatase inhibitors, 5α-reductase inhibitors and neuromuscular blocking agents etc. Versatile features of steroid-derived compounds have emerged, so the aim of the present paper is to review the recent advances of steroid-based derivatives mainly focused on their structures and biological applications, which can be employed for further development to discover potential drug candidates.

Thiadiazolodiazepine analogues as a new class of neuromuscular blocking agents: Synthesis, biological evaluation and molecular modeling study.

The synthesis, biological evaluation and molecular modeling study of 6,7-dihydro-[1,3,4] thiadiazolo[3,2-a][1,3]diazepine analogues as new class of neuromuscular blocking agents are described. The new compounds act via competitive mechanism with ACh which could be reversed by the anticholinesterase - Physostigmine. Compounds GS-53 (30) and AAH1 (33) induced dose-dependent neuromuscular blockade with onset time of 3 and 10 min, ED50 0.15 and 0.36 mmol/kg i.p., respectively, in rats. Compound 30 proved to be as twice as potent as 33 with rapid onset and shorter duration (P < 0.05). Docking profile of 30 and 33 closely resembles HIE-124 (3), in α7ß2 nAChR receptor. Molecular modeling analysis indicated that hydrogen bonding to Thr120 and Thr124 beside hydrophobic interactions play effective role incorporating the active ligands to nAChR. The obtained model could be useful for further development of new skeletal muscle relaxants.

Recent advances in neuromuscular blocking agents.

Since the introduction of (+)-tubocurarine into anaesthetic and surgical practice (1942), a number of non-depolarizing neuromuscular blocking agents (NMBs) with improved pharmacological properties have been developed during the last sixty years. However, after withdrawal of rapacuronium from clinical use, there is still a need for an ultra-short acting non-depolarizing muscle relaxant with rapid onset as substitution for the polarizing suxamethonium, which has several undesirable side-effects. In this paper, structure-activity relationships within four different series of NMBs (tetrahydroisoquinolinium, bistropinyl diester, aminosteroid, and amino peptide analogues) published in this millennium have been reviewed. The NMB properties of the most promising drug candidates from each series were discussed and compared to those of the already existing muscle relaxants.

3,16-Bisquaternary ammonium steroid derivatives as neuromuscular blocking agents: synthesis and biological evaluation.

Neuromuscular blocking agents (NMBAs) are widely used in surgery to achieve skeleton muscles relaxation under light anesthesia status. In this work, we synthesized a series of 3,16-bisquaternary ammonium steroidal NMBAs. Among them, three compounds exhibited higher in vitro activities than the commenced drug rocuronium. In addition, structure-activity relationship was unveiled. We found that the intact acetylcholine-like moiety in D-ring was not necessary for maintaining activity but both the acetyl group and the quaternary nitrogen were very essential.

Monoquaternary neuromuscular blocking agents based on 1-tetralone and 1-indanone.

The preparation of three isomeric 1-tetralone hydrozones 4 and three isomeric 1-indanone hydrozones 5 possessing a single quaternary ammonium center is described. Several of the compounds possessed significant neuromuscular blocking activity, and two approached suxamethonium in potency. 1H NMR evidence obtained from a study of the N,N-dimethylhydrozones indicated that the hydrazones adopted an E configuration in solution.

Neuromuscular blocking activity and therapeutic potential of mixed-tetrahydroisoquinolinium halofumarates and halosuccinates in rhesus monkeys.

Structure-activity relationships in rhesus monkeys for a novel mixed-onium class of ultra-short-acting nondepolarizing tetrahydroisoquinolinium neuromuscular blockers (NMBs) are described. Bis-onium chlorofumarate 20a with (1R,2S)-benzyltetrahydroisoquinolinium groups was a potent lead compound (ED(95) = 0.079 mg/kg) with an ultra-short duration of NMB effect (7.1 min) and a selectivity index (SI: defined as a ratio of the cardiovascular threshold dose to the ED(95)) similar to that of mivacurium (3). The mean threshold dose for cardiovascular effects with 20a was ca. 20 times its ED(95) value (SI = 20). A novel mixed-onium analogue of 20a was prepared by replacing the benzyltetrahydroisoquinolinium group distal to the fumarate chlorine atom with a (1S,2R)-phenyltetrahydroisoquinolinium moiety. The resulting mixed-onium chlorofumarate 24a displayed good NMB potency (ED(95) = 0.063 mg/kg), ultra-short duration of action (5.6 min) and an improved selectivity index (SI = 57). Several other mixed-onium derivatives containing octanedioate (25a; ED(95) = 0.103 mg/kg), difluorosuccinate (27c; ED(95) = 0.056 mg/kg), and fluorofumarate (28a; ED(95) = 0.137 mg/kg) linkers were also potent, ultra-short-acting NMBs with good to excellent selectivity index values (SI = 37-96). Octanedioate 25a was longer acting at higher doses compared to difluorosuccinate 27c and chlorofumarate 24a. Durations of NMB effect following a 0.4 mg/kg bolus dose (100% block) of 25a, 27c, and 24a were 16.9, 13.0, and 10.0 min, respectively. Recovery time for mixed-onium chlorofumarate 24a following a 1 h continuous infusion at 10-20 microg/kg/min (95-100% block) was ca. 5 min which is similar to that observed following a 0.2 mg/kg bolus dose of this compound and indicates a lack of cummulative effects. Preliminary studies with chlorofumarate 24a in whole human blood revealed that mixed-onium thiazolidine 29 was the major metabolite and that plasma cholinesterases do not play the primary role in duration of NMB effect. The NMB properties of 24a in rhesus monkeys led to its clinical evaluation as a possible alternative to succinylcholine.

Synthesis of ultra-short-acting neuromuscular blocker GW 0430: a remarkably stereo- and regioselective synthesis of mixed tetrahydroisoquinolinium chlorofumarates.

[formula: see text] The stereo- and regioselective synthesis of ultra-short-acting nondepolarizing neuromuscular blocker GW 0430 (5a) is described. Key steps involved the enantioselective transfer hydrogenation of imine 8 employing Noyori's catalyst, the stereoselective crystallization and methanolysis of trans-bataines 11 and 12, and the stereo- and regioselective trans elimination of hydrogen chloride from 14. The latter transformation allowed complete control of the position of the chloro substituent and stereochemistry at the double bond of the linker in 15.

Study on steroidal oximinoethers: synthesis and stereostructure by NMR spectroscopy.

The condensation of O-substituted hydroxylamines with conjugated 3-oxo-4-en steroids results in a mixture of syn-anti configurations. Syn-anti ratios are influenced by sterical hindrance between the oximino substituents (e.g. O-benzyl) and the steroidal skeleton. Stereostructures and isomeric ratios were proved by detailed 1H and 13C NMR studies and also by using 2D-COSY, 2D-HSC, DEPT, 2D-COLOC and DNOE measurements.

Synthesis, stereochemical analysis, and neuromuscular blocking activity of oximino ether derivatives of progesterone.

This study consists of the synthesis, separation, and stereochemical analysis of oximino ethers, followed by a preliminary pharmacological evaluation for neuromuscular blockade. Synthesis of the compounds began with the double oximation of progesterone, which yielded EE and ZE dioximes as major products. Both stereoisomers were separated and purified by chromatography followed by crystallization. The diether of each dioxime was prepared by O-alkylation with 2-dimethylaminoethyl chloride hydrochloride, using a mixture of potassium tert-butoxide and sodium hydride as base. The diethers were separated from the monoethers by vacuum chromatography. Configurational assignments of all compounds were based on 1HNMR and 13CNMR spectroscopy. Quaternization with methyl bromide yielded the salts which were purified via fractional crystallization. A preliminary pharmacological evaluation was conducted by using mice on a treadmill apparatus. Structure-activity relationships are discussed on the basis of similarities to succinylcholine.

Synthesis, stereochemical analysis, and neuromuscular blocking activity of selected E,E- and Z,Z-isomeric O-ethers of 4-androstene-3,17-dione dioximes.

A number of selected geometric oxime ethers were synthesized as potential neuromuscular blocking agents. The study consisted of the synthesis, separation, and stereochemical analysis of selected compounds followed by a preliminary pharmacological evaluation for neuromuscular blockade. Synthesis of the compounds began with the double oximination of 4-androstene-3,17-dione followed by TLC, column chromatography, and fractional crystallization as the purification methods. These procedures yielded two of the possible four isomers. Configurational assignments on the isolated pair were based on experiments using IR, UV, and NMR spectroscopy. Isomerically pure diethers were prepared by two methods: (a) O-alkylation of the stereochemically pure dioximes with the appropriate aminoalkyl halide, and (b) O-alkylation of the dioxime mixture followed by quaternization and subsequent isolation of configurationally pure salts via fractional crystallization. A preliminary pharmacological evaluation was conducted by using mice on a treadmill apparatus. Some structure--activity relationships are discussed.

Structure-neuromuscular blocking activity relationships of ketophosphonium salts.

Three ketophosphonium salts containing a morpholino group were prepared and evaluated for their neuromuscular blocking effect. Solution and crystal conformations were studied. An attempt was made to explain, in structural terms, different activity levels in connection with the interatomic distances.

Synthesis and neuromuscular blocking activity of 16beta-piperidinosteroidal derivatives.

The synthesis and pharmacological profiles of some new steroidal mono- and bisquaternary ammonium derivatives have been described. The compounds featured have been conceptually derived structurally from two lead structures: pancuronium bromide 1 and chandonium iodide 2. In vitro and in vivo neuromuscular blocking studies have indicated the monoquaternary compound 15 to be less active than the bisquaternary compounds 10 and 11. The compound 11 has been found to be more active than d-tubocurarine.

Synthesis and neuromuscular blocking activity of 16beta-N-methylpiperazino steroidal derivatives.

Steroidal quaternary ammonium compounds 12 and 13 with quaternised nitrogen at positions 3 and 16 of the steroidal nucleus in androstane series were synthesised and their neuromuscular blocking activities and ganglion blocking activities were studied using chick biventer and anaesthetised cat as the models. The bisquaternary compounds 12 and 13 have been found to be greater in potency than D-tubocurarine. Acetoxy derivative 13 has been found to be more potent than pipecuronium bromide taking D-tubocurarine as the standard compound indicating the need of acetoxy function at position 16.

[Synthesis of a new neuromuscular blocking agent, pipecuronium bromide (Arduan)]. / Egy új neuromuszkuláris blokkoló, a pipecuronium bromid (ARDUAN) szintézise.

A series of bisquaternary ammonio steroids having androstane skeleton have been prepared some of which possessed high neuromuscular blocking activity. One of the series 3 alpha, 17 beta-diacetoxy-2 beta, 16 beta-bis (4,4-dimethyl-1-piperazinyl)-5 alpha-androstane dibromide (19, pipecuronium bromide, ARDUAN) has proved to be a clinically useful agent of long duration of action without side effects. The preparation of pipecuronium bromide and its metabolites and the impurities are also described. The structure of 19 and related compounds was elucidated by spectrometric methods IR, NMR and MS.

[Analysis of steroids. Part 44: Analytical investigation of the intermediates of the synthesis of pipecuronium bromide (Arduan)]. / Adatok a szteránvázas vegyületek analitikájához 44. Pipecuronium bromid (Arduan) szintézis intermedierjeinek analitikája.

The following methods are described for the analytical investigation of the intermediates of the synthesis of pipecuronium bromide (Arduan) (for the numbering of the intermediates and their impurities see Figure 1.). 1. Gas chromatographic methods (capillary GC using fused silica capillaries Ultra-2 and Silar 10C WCOT) for the impurity profiling of intermediates I, II, IV and V including the identification and spectroscopic characterization of their impurities; 2. TLC methods for the similar characterisation of the further intermediates (III, VI, VII and VIII); 3. Gas chromatographic assay methods for IV and V using fused silica capillary technique and internal standards; 4. Potentiometric titration methods for the determination of VII and VIII using 0.1 M hydrochloric acid as the titrant.

16-morpholino quaternary ammonium steroidal derivatives as neuromuscular blocking agents: synthesis, biological evaluation and in silico probe of ligand-receptor interaction.

A series of steroidal 3,16-bis-quaternary ammonium salts were synthesized and screened on mouse hemi-diaphragm to explore new steroidal neuromuscular blocking agents. There were two compounds, 3ß-piperidino derivate 8d (IC(50) = 3.49 µM) and 3ß-N-methylbenzylamino derivate 8g (IC(50) = 4.54 µM), showing activity close to rocuronium (IC(50) = 2.50 µM). The preliminary structure-activity relationship was deduced from the bioactivity results with the aid of the calculated N-N distance and log P. Meanwhile, the interactions between the ligand and binding pocket were revealed by docking 8d to the ligand binding domain of the mouse muscle nicotinic acetylcholine receptor (nAChR). This nAChR was modeled using Molecular Operating Environment (MOE) package indirectly from mollusca acetylcholine binding protein with mouse neuron α7 nAChR as intermediary template.