Novel eugenol bearing oxypropanolamines: Synthesis, characterization, antibacterial, antidiabetic, and anticholinergic potentials

Five oxypropanol amine derivatives that four of them are novel have been synthesized with high yields and practical methods. in vitro antibacterial susceptibility of Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus strains to synthesized substances were evaluated with agar well-diffusion method by comparison with commercially available drugs. Most of the bacteria were multidrug resistant. It was concluded that these compounds are much more effective than reference drugs. These eugenol bearing oxypropanolamine derivatives were also effective inhibitors against α-glycosidase, cytosolic carbonic anhydrase I and II isoforms (hCA I and II), and acetylcholinesterase (AChE) enzymes with K_i values in the range of 0.80 ± 0.24-3.52 ± 1.01 µM for hCA I, 1.08 ± 0.15-3.64 ± 0.92 µM for hCA II, 5.18 ± 0.84-12.46 ± 2.08 µM for α-glycosidase, and 11.33 ± 2.83-32.81 ± 9.73 µM for AChE, respectively.

Design, synthesis, and insecticidal activity evaluation of novel 4-(N, N-diarylmethylamines)furan-2(5H)-one derivatives as potential acetylcholine receptor insecticides

BACKGROUND

Flupyradifurone is a member of a novel class of insecticides that possess excellent insecticidal activities. Halogen-containing phenyl groups are important and indispensable structural components of many pesticides. However, replacement of the difluoromethyl group of flupyradifurone with halogen-containing phenyl groups has not been reported. Hence, a series of novel butenolide derivatives containing phenyl groups were synthesized and bioassayed to discover novel compounds with excellent insecticidal activities.

RESULTS

Some target molecules exhibited good insecticidal activities against Aphis craccivora. Among the title compounds, 4cc showed the best insecticidal activities with an 50% lethal concentration (LC₅₀ ) value of 1.72 μg mL^-1 , which is superior to that of pymetrozine (LC₅₀  = 6.86 μg mL^-1 ). Molecular docking indicated that 4cc lacks oxidative metabolism by CYP6CM1 and metabolic resistance with imidacloprid. Furthermore, label-free quantitative proteomic analysis indicated that 4cc may be a potential acetylcholine receptor insecticide that acts on the nicotinic acetylcholine receptor. Compound 4cc also decreased the capability for oxidative metabolism, which further supported the molecular docking results.

CONCLUSION

This work can be used to further investigate the mechanism underlying the insecticidal activity of butenolide derivatives and develop potential novel butenolide insecticides. © 2018 Society of Chemical Industry.

Synthesis and pharmacological effects of new, N-substituted soft anticholinergics based on glycopyrrolate

To reduce the possibility of systemic side-effects in locally administered anticholinergics, two new N-substituted glycopyrrolate analogues designed using soft drug design approaches have been synthesized and evaluated in vitro and in vivo. Because stereospecificity is known to be important at muscarinic receptors, the new compounds SGM and SGE also have been prepared as their pure 2R isomers, 2R-SGM and 2R-SGE, by starting from optically pure (-)-cyclopentylmandelic acid, and the corresponding isomers were indeed found to be more active. The new soft glycopyrrolates were chemically more stable under acidic conditions, and the ethyl esters SGE were more stable than the methyl esters SGM. The new compounds were also found to be quite susceptible to extrahepatic metabolism, having half-lives of 20–30 min in rat plasma (in vitro), consistent with their soft nature. Binding studies at human muscarinic receptors (M1−M4) and guinea-pig ileum assays found 2R-SGM and 2R-SGE to have potencies somewhat less than, but close to, those of glycopyrrolate and N-methylscopolamine. They caused pupil dilation in rabbit eyes, but their mydriatic effects lasted for considerably less time than that of glycopyrrolate, and they did not induce dilation of the pupil in the contralateral, water-treated eyes, indicating that, in agreement with their soft nature, they are locally active, but safe and with a low potential to cause systemic side-effects.

Synthesis of a quaternary bis derivative of imipramine as a novel compound with potential anti-enuretic effect

OBJECTIVES

Imipramine has been used for over four decades (early reports in 1960s) for the treatment of nocturnal enuresis, although the reason for its effect is not clear. Imipramine is a tertiary amine, which may act both in the periphery and/or pass through the blood-brain barrier (BBB) in unionized form and exhibit a central effect. Since imipramine has anti-cholinergic properties, some believe it may exert its anti-enuretic effect by affecting peripheral cholinergic receptors, i.e. its anti-enuretic effect may be due to peripheral anti-cholinergic properties, whereas others think it can pass through the BBB and interact with central nervous system (CNS) receptors. If the anti-enuretic effect of imipramine is due to its peripheral anti-cholinergic effects, its entrance into the CNS is unnecessary. Therefore, the synthesis of a form of imipramine that can exhibit peripheral anti-cholinergic effects but does not have CNS adverse effects would have a safer drug profile in this case. On the other hand, if the anti-enuretic effect of imipramine is primarily due to its action on the CNS, a form of imipramine that cannot pass through the BBB has no effect on nocturnal enuresis treatment and thus may help to clarify the mechanism of action of imipramine in nocturnal enuresis treatment.

METHODS

This article describes the synthesis and evaluation of the anti-cholinergic effect of a new bis derivative of imipramine, which contains two imipramine units in its structure.

KEY FINDINGS

The compound exhibited anti-cholinergic activity comparable with that of imipramine on isolated guinea pig ileum.

CONCLUSIONS

Being a quaternary ammonium, this compound is not expected to be able to cross the BBB and thus would cause fewer CNS side effects.

Design, synthesis and histamine H1-receptor antagonistic activity of some novel 4-amino-2-(substituted)-5-(substituted) aryl-6-[(substituted aryl) amino] pyrimidines

A series of 4-amino-2-(substituted)-5-(substituted)aryl-6-[(substituted)aryl)-amino]pyrimidines was designed based on the triangular pharmacophoric requirements for histamine H1-receptor antagonists. The designed molecules were synthesized by condensation of arylacetonitriles with respective arylisothiocyanates to form corresponding acrylonitriles followed by cyclocondensation with carboxamidines to afford substituted pyrimidines. All compounds were screened for their histamine H1-receptor antagonistic activity using the model "Inhibition of the isotonic contraction induced by histamine on isolated guinea pig ileum". Target compounds were also evaluated for their sedative potential as well as their anticholinergic activities as these two are known to be the common adverse effects of histamine H1-receptor antagonists. Compounds 2h, 2i, 2j and 2k exhibited potent histamine H1-receptor antagonistic activity, which was found to be comparable with the standard drug, cetirizine (CAS 83881-51-0) and more potent than the conventional drug mepyramine (CAS 91-84-9). Some of the compounds have displayed very low sedative potential compared to diphenhydramine (CAS 58-73-1), but was found higher than cetirizine. None of them showed anticholinergic activity indicating potentialities of this series to be developed as second-generation histamine H1-receptor antagonists.

Stereoisomers of N-substituted soft anticholinergics and their zwitterionic metabolite based on glycopyrrolate--syntheses and pharmacological evaluations

PURPOSE

In this study, isomers of two N-substituted soft anticholinergics based on glycopyrrolate, SGM (PcPOAGP_NA.Me) and SGE (PcPOAGP_NA.Et) [3'-(2-cyclopentyl-2-phenyl-2-hydroxyacetoxy)-1'-methyl-1'-alkoxycarbonylpyrrolidinium bromide] and their zwitterionic metabolite, SGa (PcPOAGP_NA.H) [3'-(2-cyclopentyl-2-phenyl-2-hydroxyacetoxy)-1'-methyl-1'-carboxymethylpyrrolidinium inner salt] were synthesized and their pharmacological activities were evaluated in vitro and in vivo.

METHODS

The isomers of SGM and SGE were synthesized with both optically pure methyl-cyclopentylmandelate and 3-hydroxy-N-methylpyrrolidine. Trans-esterification followed by quarternization with alkyl bromoacetate gave four isomers of SGM or SGE with the nitrogen chiral center unresolved (2R3'S-SGM, 2R3'R-SGM, 2S3'S-SGM, 2S3'R-SGM or 2R3'S-SGE, 2R3'R-SGE, 2S3'S-SGE, 2S3'R-SGE). The hydrolysis of these four isomers followed by HPLC separation resulted in eight fully resolved isomers of SGa (2R3'R1'R, 2R3'S1'R, 2R3'R1'S, 2R3'S1'S, 2S3'R1'R, 2S3'S1'R, 2S3'R1'S, and 2S3'S1'S). Pharmacological activities were assessed by using in vitro receptor-binding assay and guinea pig ileum pA2-assay, and by evaluating the in vivo rabbit mydriatic effects. Results were compared to those obtained with conventional anticholinergic agents, such as glycopyrrolate, N-meythylscopolamine, and tropicamide, as well as those obtained with previously prepared racemic mixtures and 2R isomers.

RESULTS

Receptor binding pKi values at cloned human muscarinic receptors (M1-M4 subtypes) were in the 6.0-9.5 range for the newly synthesized SGM and SGE isomers, and in the 5.0-8.6 range for the SGa isomers. In all cases, 2R isomers were significantly more active than 2S isomers (27 to 447 times for SGM isomers, and 6 to 4467 times for SGa isomers). Among the four SGM isomers with unresolved 1' (N) chiral center, the 3'R isomers were more active than the corresponding 3'S isomers (1.5-12.9 times), whereas, among the SGa isomers, the 3'S isomers were not always more active than the corresponding 3'R isomers indicating that activity determined based on configuration at chiral center 3' is significantly affected by the configuration of the other two chiral centers, 2 and 1'. Among the completely resolved eight SGa isomers (all three chiral centers resolved), 1'S isomers were always more active than the corresponding 1'R isomers (1.8-22.4 times). Results also indicate that some isomers showed good M3/M2 muscarinic-receptor subtype-selectivity (about 3-5 times), and 2R and 3'S were the determining configurations for this property. Guinea pig ileum assays and rabbit mydriasis tests on SGa isomers further confirmed the stereospecificity. In rabbit eyes, some 2R-SGa isomers showed mydriatic potencies similar to glycopyrrolate and exceeded tropicamide, but their mydriatic effects lasted considerably shorter, and they did not induce dilation of the pupil in the contralateral, water-treated eye. These results indicate that these compounds are locally active, but safe and have a low potential to cause systemic side effects. The pharmacological potency of the eight SGa isomers was estimated as 2R3'S1'S approximately equal to 2R3'R1'S approximately equal to 2R3'S1'R > 2R3'R1'R > 2S3'R1'S > 2S3'S1'S approximately equal to 2S3'R1'R > 2S3'S1'R (p < 0.05).

CONCLUSIONS

The stereospecificity and M3/M2 muscarinic-receptor subtype-selectivity of soft anticholinergics, SGM, SGE, and SGa have been demonstrated. In agreement with previous results, the potential for their effective and safe use has been confirmed.

Synthesis and biological activities of some thiazolidin-4-ones

In this study, fifteen 2,3-disubstituted-4-thiazolidinone derivatives were synthesized by the reaction of Schiff bases and alpha-mercaptoacetic acid. The structures of the compounds were elucidated by IR, 1H-NMR, 13C-NMR, mass spectral data and elementary analysis. The antihistaminic and anticholinergic activities of the compounds were determined by tests performed on isolated guinea pig trachea in comparison with aminophylline (CAS 317-34-0). Compound 15 (3-[3-(2-methyl-piperidine-1-yl)propyl]-2-(4-methyl-phenyl)thiazolidin-4-one hydrochloride) showed the highest inhibition (53 %).

An efficient approach to the asymmetric total synthesis of (–)-anisodine

-Anisodine (l-6,7-epoxy-3-tropyl-alpha-hydroxytropate), which was isolated from the medicinal plant Scopolia tanguticus Maxim, was the first efficiently prepared using 6-beta-acetyltropine as the starting material via a key step of the Sharpless asymmetric dihydroxylation (AD). The intermediate compounds 10 and 11 showed promising cholinergic activity.

Preparation and biological effects of pure stereoisomeric novel soft anticholinergics

A series of pure stereoisomeric soft glycopyrrolate analogues 3, 4 and 5 was synthesized using chiral intermediates and by careful separation of the stereoisomers formed during the last quaternization step of the synthesis. The stereochemistry of the products was elucidated using various 1D and 2D NMR techniques. Anticholinergic activity of the new compounds was determined by receptor binding studies and performing tests on isolated organs and by in vivo tests. Receptor binding revealed that in the higher alkyl ester series the (2R, 1'R, 3'R) and the (2R, 1'S, 3'S) isomers were the compounds showing the highest receptor affinity furthermore it demonstrated the confines of the length of the alkyl chain. In vitro isolated organ experiments correlated well with the receptor binding results, and in vivo investigations indicated the soft character of the compounds.

Biotransformation of Desoxypeganine by Microsomal Enzymes of the Rabbit Liver

The biotransformation of the anticholinergic quinazoline alkaloid Desoxypeganine is studied by means of aerobic incubation with the non-induced supernatant obtained at 9000g from rabbit liver homogenates as enzyme source followed by an admixture of NADPH. The metabolites were identified by high-performance liquid chromatography, chemical ionisation mass spectrometry (LC-CI MS) and electron impact mass spectrometry (LC-EI MS) in comparison with synthetic reference compounds and typical ion fragments taken from literature data. C-oxidation of Desoxypeganine to the major metabolite Pegenone was observed as well as the hydroxylation of the alicyclic ring. The incubation mixture followed Michaelis-Menten kinetics characterised by K(m) = 5.8 x 10(-5) mol L(-1) and V(max) = 4.32 nmol Pegenone/min per mg protein or 3.37 nmol Pegenone/min per nmol CYP 450, respectively. These in vitro results demonstrate that the bioactive substance Desoxypeganine is easily oxidised to its ineffective metabolite Pegenone. This provokes a problem for correct dosage finding in formulations for the treatment of Alzheimer's disease and in the therapy of alcoholism and nicotine dependence.

1-Azaadamantanes: pharmacological applications and synthetic approaches

1-Azaadamantane (1-azatricyclo [3.3.1.1(3,7)]decane) was synthesized in 1953, and the derivatives have been used as rigid models for studies on intramolecular charge transfer phenomena, fluorescence excitation Rydberg states, highly twisted amides, solid electrolyte gas sensors, basicities, and self-organization systems. These structures have also been attracting considerable interest due to their pharmacological activities. The substituted 1-azaadamantanes as conformationally restricted amines have great potential for the therapeutic utilization as anticholinergic agents, serotonergic agents, and squalene synthase inhibitors. However, many steps have been needed for the synthesis of 1-azaadamantanes, and the concise synthetic approaches have been developed. Though double or triple Mannich reactions yield 1-azaadamantanes in moderate yields, the reduction steps are necessary. Our recent research has revealed that trifluoromethanesulfonic anhydride is available for the convenient synthesis of 1-azoniaadamantanes and 1-azaadamantanes without reduction. The new tools for the discovery of novel drugs such as quantitative structure-activity relationship (QSAR) analysis and vibrational circular dichroism (VCD) spectroscopy have also been discussed.

Design, pharmacokinetic, and pharmacodynamic evaluation of soft anticholinergics based on tropyl alpha-phenylcyclopentylacetate

Four new soft anticholinergic agents based on tropyl alpha-phenylcyclopentylacetate, 15a, 15b, 18a, and 18b, were designed and synthesized. Receptor binding studies on the cloned human muscarinic receptors indicated that the new soft anticholinergic agents possessed moderate potency as pKi ranged from 6.7 to 7.6. Mydriatic studies in rabbit eyes revealed that the duration of the action of the new soft anticholinergics (8.5-11.0 h) were shorter than that of atropine (about 24 h) under pharmacodynamic equivalent dose, and one of them, 18a, showed even shorter than that of tropicamide. In addition, after unilateral administration, significant dilation of pupil in the control eyes was observed with tropicamide and atropine but not with soft drugs, suggesting the systemic activity of soft drugs was minimal. With their soft nature, the new soft anticholinergics displayed much shorter protective effect against carbachol-induced bradycardia (about 30 min) than atropine (at least 60 min) in rats. In vitro and in vivo pharmacokinetic studies demonstrated that the soft anticholinergics were rapidly hydrolyzed into the corresponding inactive metabolites once they were introduced into the systemic circulation.

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.

Receptor binding studies of soft anticholinergic agents

Receptor binding studies were performed on 24 soft anticholinergic agents and 5 conventional anticholinergic agents using 4 cloned human muscarinic receptor subtypes. The measured pK(i) values of the soft anticholinergic agents ranged from 6.5 to 9.5, with the majority being in the range of 7.5 to 8.5. Strong correlation was observed between the pK(i) s determined here and the pA 2 values measured earlier in guinea pig ileum contraction assays. The corresponding correlation coefficients (r2) were 0.80, 0.73, 0.81, and 0.78 for pK(i) (m1), pK(i) (m2), pK(i) (m3), and pK(i) (m4), respectively. Quantitative structure-activity relationship (QSAR) studies were also performed, and good characterization could be obtained for the soft anticholinergics containing at least 1 tropine moiety in their structure. For these compounds, the potency as measured by the pK i values was found to be related to geometric, electronic, and lipophilicity descriptors. A linear regression equation using ovality (O(e)), dipole moment (D), and a calculated log octanol-water partition coefficient (QLogP) gave reasonably good descriptions (r = 0.88) for the pK(i) (m3) values.

Solid-phase synthesis and biological evaluation of a combinatorial library of philanthotoxin analogues

The modular structure of philanthotoxins was exploited for construction of the first combinatorial library of these compounds using solid-phase parallel synthesis. (S)-Tyrosine and (S)-3-hydroxyphenylalanine were used as amino acid components, spermine, 1,12-dodecanediamine, and 4,9-dioxa-1,12-dodecanediamine as amine components, and butanoyl, phenylacetyl, and cyclohexylacetyl as N-acyl groups. Following automated preparative HPLC, the resulting 18 compounds were isolated as the S-forms in 40-70% yields. The purity of the products was determined by HPLC with evaporative light scattering detection and by (1)H and (13)C NMR. The thus obtained philanthotoxins were tested electrophysiologically for their antagonist properties on human muscle-type nicotinic acetylcholine receptors (nAChR) expressed in TE671 cells and on rat brain non-NMDA glutamate receptors (non-NMDAR) expressed in Xenopus oocytes. 4-Hydroxy analogues lacking the secondary amino groups (PhTX-12 and 4,9-dioxa-PhTX-12 and their analogues) were inactive on non-NMDAR, whereas the potency of the spermine derivatives (PhTX-343 and its analogues) increased with steric bulk of the N-acyl group. The analogue of PhTX-343 in which the N-butanoyl group was replaced by phenylacetyl group had IC(50) of 15 +/- 4 nM on non-NMDAR. Increasing the steric bulk of the N-acyl group was not advantageous for activity at nAChR, and a sharp decrease in potency with increased steric bulk was observed with the derivatives of PhTX-12. 3-Hydroxy analogues generally exhibited lower activity and different response to alterations of the N-acyl groups as compared to the 4-hydroxy analogues. Since the acyl group alterations in PhTX-343 and 4,9-dioxa-PhTX-12 have a similar effect on potency, which is distinctly different from that observed for PhTX-12, the two former compounds may bind to nAChR in a similar fashion but differently from that of PhTX-12. The combinatorial library approach described in this work represents a prototype methodology for future exploration of structure-activity relationships of philanthotoxins.

Synthesis and pharmacology of new dithiocarbamic acid esters derived from phenothiazine and diphenylamine

2-Methylthio-10-[(N,N-disubstituted-thiocarbamoylthio)acetyl]- phenothiazines (4a-g) and N-(3-methylthiophenyl)-N-[(N,N-disubstituted- thiocarbamoylthio)acetyl]phenylamines (5a-g) were synthesized by subsequent treatment of 2-methylthio- 10-chloroacetylphenothiazines (1) and N-(3-methylthiophenyl)-N-chloroacetylphenylamine (2) with potassium salts of N,N-disubstituted dithiocarbamic acid derivatives (3a-i). The structures of the compounds were determined by analytical and spectral (IR, 1H NMR, 13C NMR, EIMS) methods. The antihistaminic and anticholinergic activities of 4a, 4c, 4e-g, 5a-c, 5e, and 5 g were evaluated in comparison with H1-receptor antagonist mepyramine and nonselective cholinergic antagonist atropine. In the first series of experiments, the cumulative concentration-response curves to histamine (10(-8)-10(-4) M) and acetylcholine (10(-8)-10(-4) M) were constructed in seperate fundus strips. The test compounds exhibited marked antihistaminic activity at 10(-6) M concentration but compounds did not influence acetylcholine induced contractions. Concentration-related experiments carried out on 4 g and 5 g revealed that a moderate antihistaminic activity was present at 10(-7) M concentration of the compounds and became strong at higher concentrations. In the second series of experiments, the cumulative concentration-response curve to histamine (10(-9)-10(-4) M) was constructed in guinea-pig ileum segments. Maximal responses were obtained by 10(-6)-3 x 10(-6) M concentrations of histamine in ileum segments. Similar inhibitions of histamine contractions were also obtained with the test compounds. Their inhibitory effectiveness was evaluated by comparing the pA2 values.

[The preparation and bioactivities of chiral analogs of baogongteng A]

Eight chiral analogs of baogongteng A were prepared from (+/-)-3 alpha-hydroxy-6 beta-acetoxytropane by chemical resolution. In myotic or mydriatic tests in rabbits, (-)-3 alpha-paramethyl benzenesulfonyloxy-6 beta-acetoxytropane showed cholinergic activities, while (+)-3 alpha-benzoyloxy-6 beta-acetoxytropane and (+)-3 alpha-parachloro benzoyloxy-6 beta-acetoxytropane showed anticholinergic activities.

New 5-aminoacyl-5,10-dihydro-11H-dibenzo[b,e][1,4]diazepin-11-ones with antiarrhythmic activity

A series of new 5-substituted tricyclic 5,10-dihydro-11H-dibenzo[b,e][1,4]-diazepin-11-ones was identified as potential antiarrhythmic agents against bradyarrhythmias [1, 2]. The in vitro and in vivo interactions of the compounds with muscarinic receptors and the antiarrhythmic activity were examined. In receptor binding studies some derivatives showed a high affinity to the cardiac M2 receptor (Ki 10 nmol/l), an equal or smaller affinity to cortical M1 receptor and a lower affinity to the glandular M3 binding site. Functional experiments showed the derivatives as competitive antagonists with high affinity to the cardiac and smaller affinity to the intestinal muscarinic receptor. In vivo experiments correspond with the M2 selectivity. First the vagal or agonist-induced bradycardia was inhibited in rats and guinea pigs while the McNA-343 induced increase of blood pressure, methacholine-induced bronchi and bladder constriction as well as the salivation were inhibited only at higher doses. In conscious cats the tachycardia was examined in comparison with pupillomotoricity. The effect duration and the therapeutical range were determined in comparison to the M2 selective blocking agent AF-DX116. The antiarrhythmic activity was examined compared to quinidine sulfate in CaCl2-arrhythmia of rats, in atrial fibrillation and atrial flutter in dogs according to Scherf [2] and in electric induced atrial fibrillation under vagal stimulation in cats. In the atrial arrhythmias the derivatives are clearly longer effective than quinidine sulfate. The antiischemic activity was examined in the two-stages coronary ligature in dogs according to Harris. The long-running regularization of ectopies (about 2 h after i.v. injection) occurred without decrease of the heart rate, an effect particularly convenient to therapy of bradycardic dysrhythmias.

6-Hydroxycatecholine, a choline-mimicking analogue of the selective neurotoxin, 6-hydroxydopamine

The synthesis and properties of 6-hydroxy-N,N-dimethylepinephrine (6-hydroxy-catecholine) are reported. This agent is intended for use as a selective presynaptic cholinotoxin and is based on previously reported neurotoxins of the same type. 6-hydroxycatecholine is a close structural analogue of the catecholaminergic neurotoxin 6-hydroxydopamine, and is expected both to be selectively reactive at cholinergic sites and to undergo less vigorous and potentially more selective inactivating reactions. It is also possible that in specific dementia-inducing pathologies, 6-hydroxycatecholine could be formed endogenously.

Soft drugs. 21. Design and evaluation of soft analogs of propantheline

The soft drug approach was applied to synthesize seven soft analogs of propantheline, which by design display predictable and controllable decomposition to inactive metabolites. Their synthesis involved the quatemization of several different amine groups with the chloromethyl ester of 9-methylxanthene-9-carboxylic acid. The rates of disappearance were measured for all of the compounds and were found to be more rapid than that of propantheline bromide in a variety of chemical and biological media under in vitro conditions. One of the soft analogs was found to be equipotent with propantheline in an in vitro assay. This soft analog was found to be equipotent with propantheline, in vivo, in protecting the rats against indomethacin-induced gastric ulceration and in inducing mydriasis in rabbits on intravenous administration. The pupil sizes returned faster to predrug levels with the soft analog than with propantheline, indicating increased metabolic lability of the soft analog. The equipotency of this soft analog coupled with increased metabolic lability proves the rationality of the soft drug approach for the design of safer therapeutic agents with higher therapeutic indices.