Carbamate Moiety Research Articles

Recent Approaches to Novel Anti-Alzheimer Therapy

Insufficient cholinergic neurotransmission in AD is responsible for a progressive loss of cognition and motor capacities. The cholinergic hypothesis has provided the rationale for the current treatment approaches based on acetylcholinesterase inhibitors. However, recent data focus on the complex nature of AD and disclose the involvement of other neurotransmitters such as serotonin, noradrenalin, dopamine, histamine, excitatory amino acids and neuropeptides among others. Interestingly, recent research has revealed that in severe AD brains the levels of AChE are considerably reduced whereas BuChE activity increases, thus aggravating the toxicity of beta A. In such instances, it is possible that BuChE may be a more suitable target than AChE. Oxidative stress has been implicated in CNS degenerative disorders such as AD and PD. Therefore, owing to their capacity to inhibit oxidative damage, MAOIs are potential candidates as anti-Alzheimer drugs. More recently, a novel drug--TV3326--was designed, based upon two pharmacophores: the carbamate moiety from rivastigmine, an AChE inhibitor; and the propargyl group from rasagiline, a MAO inhibitor. This drug exhibits cholinesterase and selective brain MAO inhibitory activities, reduces apoptosis and stimulates the processing of APP alpha, hence reducing the possibility of generation of the toxic beta A. Thus, TV3326 may be expected to contribute positively to the cognitive benefits of Alzheimer's patients. Anyhow, the development of drugs with several targets and diverse pharmacological properties may conclusively demonstrate the most beneficial therapy.

A New Strategy Toward Indole Alkaloids Involving an Intramolecular Cycloaddition/Rearrangement Cascade.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A new strategy toward indole alkaloids involving an intramolecular cycloaddition/rearrangement cascade.

The intramolecular Diels-Alder reaction between an amidofuran moiety tethered onto an indole component was examined as a strategy for the synthesis of Aspidosperma alkaloids. Furanyl carbamate 23 was acylated using the mixed anhydride 26 to provide amidofuran 22 in 68% yield. Further N-acylation of this indole furnished 27 in 88% yield. Cyclization precursors were prepared by removing the carbamate moiety followed by N-alkylation with the appropriate alkyl halides. Large substituent groups on the amido nitrogen atom causes the reactive s-trans conformation of the amidofuran to be more highly populated, thereby facilitating the Diels-Alder cycloaddition. The reaction requires the presence of an electron-withdrawing substituent on the indole nitrogen in order for the cycloaddition to proceed. Treatment of N-allyl-bromoenamide 48 with n-Bu(3)SnH/AIBN preferentially led to the 6-endo trig cyclization product 50, with the best yield (91%) being obtained under high dilution conditions. The initially generated cyclohexenyl radical derived from 48 produces the pentacyclic heterocycle 50 by either a direct 6-endo trig cyclization or, alternatively, by a vinyl radical rearrangement pathway.

Structure‐Reactivity Relationships as Probes to Acetylcholinesterase Inhibition Mechanisms by Aryl Carbamates. II. Hammett‐Taft Cross‐Interaction Correlations

AbstractSubstituted phenyl‐N‐butyl carbamates (1) and p‐nitrophenyl‐N‐substituted carbamates (2) are characterized as “pseudo‐pseudo‐substrate” inhibitors of acetylcholinesterase. Since the inhibitors protonate in pH 7.0 buffer solution, the virtual inhibition constants (Ki's) of the protonated inhibitors can be calculated from the equation, ‐logKi' = ‐logKi ‐ pKa + 14. The ‐logKi' and logkc values for acetylcholinesterase inhibitions by carbamates 1 correlate with the Hammett equation (log(k/k0) = ρσ); moreover, those by carbamates 2 correlate with the Taft equation (log(k/k0) = ρ* σ*). With modified Hammett‐Taft cross‐interaction variations, multiple linear regressions of the ‐logKi' and logkc values of carbamates 1 and 2 give good correlations, and the cross‐interaction constants (ρXR) are 0.5 and 0.0, respectively. The ρXR value of 0.5 indicates that the carbamate O‐C(O)‐N‐R geometries for the transition states that lead to enzyme‐carbamate tetrahedral intermediates are all pseudo‐trans conformations. Therefore, the carbamate moiety of the inhibitors stretches along the active site gorge of the enzyme but does not bind in the acyl binding site pocket of the enzyme. Overall, the carbamate O‐C(O)‐N‐R geometries for carbamates 1 and 2, protonated carbamates 1 and 2, and the tetrahedral intermediate are all retained in pseudo‐trans conformations. The ρXR value of 0.0 suggests that the transition states that lead to the carbamyl enzymes are breaking C‐O bonds and are excluding the leaving groups, substituted phenols.

Synthesis of Cationic Cholesterol Derivatives with Fragments of Aliphatic Nitrogen-Containing Bases

Cationic cholesterol derivatives were synthesized, in which fragments of aliphatic amines (2-di-methylaminoethanol, N,N-dimethylethylenediamine, and N,N,N',N'-tetramethylethylenediamine) are attached to the cholesterol backbone either directly or through a spacer ester or carbamate moiety. The products may be used as efficient agents for liposome-mediated transfection.

Carbamoylcholine homologs: novel and potent agonists at neuronal nicotinic acetylcholine receptors.

The classic muscarinic acetylcholine receptor (mAChR) agonist carbamoylcholine (carbachol) does not seem to be the most obvious lead for the development of selective ligands at nicotinic acetylcholine receptors (nAChRs). In the past, however, N-methylations of carbachol have provided N-methylcarbamoylcholine and N,N-dimethylcarbamoylcholine (DMCC), which predominantly display nicotinic activity. In this study, 12 homologous analogs of DMCC and its corresponding tertiary amine, N,N-dimethylcarbamoyl-N,N-dimethylaminoethanol, were synthesized and their binding affinities to native mAChR and nAChR sites estimated. One of the compounds in the series, 3-N,N-dimethylaminobutyl-N,N-dimethylcarbamate (7), displayed low nanomolar binding affinity to nAChRs and a 400-fold selectivity for nAChRs over mAChRs. Hence, a new series of compounds was synthesized in which alkyl and aryl groups and different ring systems were introduced in the carbamate moiety of 7. In a [3H]epibatidine binding assay, the Ki values of 7 and its analogs at rat alpha2beta2, alpha4beta2, alpha2beta4, alpha3beta4, and alpha4beta4 nAChRs, stably expressed in mammalian cell lines, ranged from low nanomolar to midmicromolar concentrations, whereas all of the compounds displayed weak binding to an alpha7/5-HT3 chimera and to native mAChRs. Compound 7 and its analogs were determined to be agonists at the alpha3beta4 nAChR subtype. This series includes the most potent and selective nicotinic agonists structurally derived from ACh to date. Furthermore, the compounds are tertiary amines, implying some advantages in terms of bioavailability pertinent to future in vivo pharmacological studies. Finally, observations made in the study hold promising perspectives for future development of ligands selective for specific nAChR subtypes.

Biological evaluation of sphingomyelin analogues as inhibitors of sphingomyelinase.

Seeking neutral sphingomyelinase inhibitors, we designed and synthesized hydrolytically stable analogues of sphingomyelin. These novel analogues replace the phosphodiester moiety of sphingomyelin with carbamate and urea moiety, resulting in inhibition of neutral sphingomyelinase. Compound 1 prevented ceramide generation and apoptotic neuronal cell death in a model of ischemia based on organotypic hippocampal slice cultures.

Mild Procedure for the Catalytic Bis(stannylation) of Alkynes with Hexaalkylditins.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Multifunctional polyesters as new candidate materials for biomedical applications. Synthesis and structural characterization

AbstractThe present work was aimed at the development of functional polymeric materials to be used in the targeted delivery of proteic drug and tissue engineering fields. The adopted strategy was based on the design of special polymer classes whose structures and functionality could be easily modified by finely tuned synthetic procedures. Poly(ether ester)s containing H‐bonding units were chosen as promising materials for the proposed applications. Commercially available precursors were successfully used for the synthesis of symmetrical diesters containing different H‐bonding groups (amide, carbamate, and urea moieties). In all cases, pure products were obtained in good yields. Bulk polycondensation of the monomeric precursors with different mixtures of 1,4‐butanediol and PEG 1000 diol afforded a variety of high molecular weight polymeric structures. Physical‐chemical characterization of the polymers indicates that their thermal, mechanical, and swelling properties can be tailored by a proper selection of the H‐bonding group and of the composition of the feed mixture.

Sphingomyelin analogues as inhibitors of sphingomyelinase.

To search for neutral sphingomyelinase inhibitors we designed and synthesized hydrolytically stable analogues of sphingomyelin. The novel compounds 8 and 9 which were replaced the phosphodiester moiety of sphingomyelin with the carbamate moiety showed inhibitory activity with an IC(50) value of micro M on neutral sphingomyelinase in rat brain microsomes. Compound 8i showed a selective neutral sphingomyelinase inhibitory activity.

Mild procedure for the catalytic bis(stannylation) of alkynes with hexaalkylditins.

[reaction: see text] Bis(stannylation) of terminal alkynes is achieved through the use of a palladium-isonitrile catalyst complex using a hexaalkylditin as a stannyl group transfer reagent in an atom-efficient and mild catalytic process. Functional group tolerance is good, allowing the presence of amine, carbamate, silyl, ester, and ether moieties. An activated internal alkyne also underwent bis(stannylation) in moderate yield, allowing access to symmetrical bis(alkenyl)stannanes.

Anti-apoptotic action of anti-Alzheimer drug, TV3326 [( N-propargyl)-(3 R)-aminoindan-5-yl]-ethyl methyl carbamate, a novel cholinesterase-monoamine oxidase inhibitor

The anti Parkinson drug, rasagiline [ R-(+)- N-propargyl-1-aminoindan], an inhibitor of type B monoamine oxidase, has been shown to suppress apoptosis induced by neurotoxins and oxidative stress. A series of novel propargylaminoindans with a carbamate moiety to inhibit cholinesterase were developed from phamacophore of rasagiline to protect or rescue deteriorated neurons in Alzheimer's and Lewy Body disease and provide a beneficial effect on the cognitive deficits. Rasagiline analogues were found to protect dopaminergic SH-SY5Y cells against apoptosis induced by peroxynitrite donor. SIN-1. TV3326, [( N-propargyl)-(3 R)-aminoindan-5-yl]-ethyl methyl carbamate, was as effective as rasagiline in preventing apoptosis, followed by its S-enantiomer, TV3279. The anti-apoptotic-neuroprotective activity was shown to reside in the propargylamine and not the carbamate moiety. This resulted in stabilization of the mitochondrial membrane potential, the collapse of which initiates the apoptotic cascade.

Synthesis and ring‐opening (co)polymerization of L‐lysine N‐carboxyanhydrides containing labile side‐chain protective groups

AbstractThis contribution describes the synthesis and ring‐opening (co)polymerization of several L‐lysine N‐carboxyanhydrides (NCAs) that contain labile protective groups at the ϵ‐NH2 position. Four of the following L‐lysine NCAs were investigated: Nϵ‐trifluoroacetyl‐L‐lysine N‐carboxyanhydride, Nϵ‐(tert‐butoxycarbonyl)‐L‐lysine N‐carboxyanhydride, Nϵ‐(9‐fluorenylmethoxycarbonyl)‐L‐lysine N‐carboxyanhydride, and Nϵ‐(6‐nitroveratryloxycarbonyl)‐L‐lysine N‐carboxyanhydride. In contrast to the harsh conditions that are required for acidolysis of benzyl carbamate moieties, which are usually used to protect the ϵ‐NH2 position of L‐lysine during NCA polymerization, the protective groups of the L‐lysine NCAs presented here can be removed under mildly acidic or basic conditions or by photolysis. As a consequence, these monomers may allow access to novel peptide hybrid materials that cannot be prepared from ϵ‐benzyloxycarbonyl‐L‐lysine N‐carboxyanhydride (Z‐Lys NCA) because of side reactions that accompany the removal of the Z groups. By copolymerization of these L‐lysine NCAs with labile protective groups, either with each other or with γ‐benzyl‐L‐glutamate N‐carboxyanhydride or Z‐Lys NCA, orthogonally side‐chain‐protected copolypeptides with number‐average degrees of polymerization ≤20 were obtained. Such copolypeptides, which contain different side‐chain protective groups that can be removed independently, are interesting for the synthesis of complex polypeptide architectures or can be used as scaffolds for the preparation of synthetic antigens or protein mimetics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1167–1187, 2003

Discovery of a long-chain carbamoyl aminocarnitine derivative, a reversible carnitine palmitoyltransferase inhibitor with antiketotic and antidiabetic activity.

The synthesis and pharmacological activity of reversible CPT I inhibitors as potential antiketotic and antidiabetic drugs are reported. Such inhibitors constitute a series of enantiomerically pure aminocarnitine derivatives having the general formula (CH3)3N+CH2CH(ZR)CH2COO- (with Z = ureido, carbamate, sulfonamide, and sulfamide moieties; R = C7-C14 linear alkyl chains). A primary pharmacological screening based on the evaluation of CPT I activity in intact rat liver (L-CPT I) mitochondria revealed the best activity for the (R) forms of ureidic derivative 17 (ZR = NHCONHR, R = C14), sulfonamidic derivative 7 (ZR = NHSO2R, R = C12), and sulfamidic derivative 9 (ZR = NHSO2NHR, R = C11). The IC50 values are 1.1, 0.7, and 0.8 microM, respectively. For the carbamic derivative 11 (ZR = NHCOOR, R = C8), an IC50 of 9.5 microM was observed. In addition, an extraordinarily high selectivity toward the liver isoform with respect to the heart isoform (muscle-CPT I identical with M-CPT I) was found for the ureidic compound 17 (IC50(M-CPT I) vs IC50(L-CPTI) = 39.4), as well as for other ureidic or carbamic compounds. Diabetic db/db mice treated orally with 17 and 7 for 45 days at a dose of 50 mg/kg twice a day showed a good reduction of serum glucose levels with respect to the untreated db/db mice (p < 0.01). In addition, 17 showed antiketotic activity in normal fasted rats. 17 has been selected for development as a potential antiketotic and antidiabetic drug.

Resolution of α-hydroxystannanes via norephedrine carbamates

Norephedrine carbamate derivatives of α-hydroxystannanes can be readily prepared and the resulting diastereomers are separable by column chromatography. Removal of the carbamate moiety by reduction provides enantiomerically-enriched α-hydroxystannanes.

Intramolecular amidofuran cycloadditions across an indole pi-bond: an efficient approach to the aspidosperma and strychnos ABCE core.

[reaction: see text] The intramolecular Diels-Alder reaction between an amidofuran moiety tethered onto an indole component was examined as a strategy for the synthesis of Aspidosperma and Strychnos alkaloids. Furanyl carbamate 13 was acylated using the mixed anhydride 16 to provide amidofuran 12 in 68% yield. Further N-acylation of this indole furnished 17 in 88% yield. Cyclization precursors were prepared by removing the carbamate moiety followed by N-alkylation with the appropriate alkyl halides. Thermolysis of 25 provided the novel tetracyclic ketone 26 in 74% yield.

Novel dual inhibitors of AChE and MAO derived from hydroxy aminoindan and phenethylamine as potential treatment for Alzheimer's disease.

Carbamate derivatives of N-propargylaminoindans (Series I) and N-propargylphenethylamines (Series II) were synthesized via multistep procedures from the corresponding hydroxy precursors. The respective rasagiline- and selegiline-related series were designed to combine inhibitory activities of both acetylcholine esterase (AChE) and monoamine oxidase (MAO) by virtue of their carbamoyl and propargylamine pharmacophores. Each compound was tested for these activities in vitro in order to find molecules with similar potencies against each enzyme. Compounds with such dual AChE and MAO inhibitory activities are expected to have potential for the treatment of Alzheimer's disease. The observed SAR also offers insight into the requirements of the active sites on these enzymes. A carbamate moiety was found to be essential for AChE inhibition, which was absent in the corresponding hydroxy precursors. The propargyl group caused 2-70-fold decrease in AChE inhibitory activity (depending on the position of the carbamoyl group) of Series I, but had little or no effect in Series II. Thus, the 6- and 7-carbamyloxyphenyls in Series I were either equipotent to, or slightly (2- to 5-fold) less active as AChE inhibitors than, the corresponding compounds in Series II, while the 4-carbamyloxyphenyls were more potent. The presence of the carbamate moiety in 6- and 7-carbamyloxyphenyls of Series I, considerably decreased MAO-A and -B inhibitory activity, compared to that of the parent hydroxy analogues, while the opposite was true for Series II. Thus, the 6- and 7-carbamyloxyphenyls in Series I were 2-3 orders of magnitude weaker MAO inhibitors while the 4- carbamyloxyphenyls were equipotent with the corresponding compounds in Series II. In both series, N-methylation of the propargylamine enhanced the MAO (A and B equally) inhibitory activities and decreased the AChE inhibitory activity. Two candidates belonging to the indan and tetralin ring systems (24c, 27b) and one phenethylamine (53d) were identified as possible leads for further development based on the following criteria: (a) comparable AChE and MAO-B inhibitory activities, (b) good to moderate AChE inhibitory activity, and (c) lack of strong MAO-A selectivity. However, it is likely that these compounds will be metabolized to the corresponding phenols, with inhibitory activities against AChE and/or MAO-A or -B, different from those of the parent carbamates. Thus, the apparent enzyme inhibition will be a result of the combined inhibition of all of these individual metabolites. The results of our ongoing in vivo screening programs will be published elsewhere.

Synthesis of four cholic acid-based CSPs containing 2-naphthoyl carbamate and 3,5-dinitrophenylcarbamate moieties and their evaluation in the HPLC resolution of racemic compounds

Four new chiral selectors, obtained by derivatising the hydroxy groups of cholic acid with 2-naphthylisocyanate and 3,5-dinitrophenylisocyanate have been prepared and linked to silica gel to obtain new chiral stationary phases (CSPs) for the HPLC separation of enantiomers. The CSP containing only 2-naphthylcarbamate groups is able to separate the enantiomers of π-acidic substrates, whereas the CSPs containing one 3,5-dinitrophenylcarbamate group and two 2-naphthyl carbamate moieties resolve π-acidic racemic compounds as well as π-basic substrates, with the observed enantiodiscriminating capabilities depending on the arrangement of the different carbamoyl units on the cholestanic backbone.

Synthesis of chiral oxazolidin-2-ones from N-alkoxycarbonyl amino epoxides: a computational studyElectronic supplementary information (ESI) available: structures of localized transition states. See http://www.rsc.org/suppdata/p1/b2/b203702e/

threo-N-Alkoxycarbonylamino epoxides 5a–d, containing the oxazolidine moiety, were converted into trans-4,5-disubstituted-2-oxazolidin-2-ones 2 with total regio- and stereoselection by means of nucleophilic intramolecular attack of the carbamate moiety to the protonated oxirane ring. Theoretical calculations confirmed both the regioselection and the preference of the cyclocarbamation reaction vs. the intermolecular attack by the solvent, arising from different behaviour in comparison with the analogous iodonium ions.

Novel uridin-2′-yl carbamates: synthesis, incorporation into oligodeoxyribonucleotides, and remarkable fluorescence properties of 2′-pyren-1-ylmethylcarbamateElectronic supplementary information (ESI) available: Additional experimental data for compounds 3, 5 and 6. See http://www.rsc.org/suppdata/p1/b1/b111434b/

A convenient method for the preparation of uridin-2′-yl carbamate derivatives is described. The stable 2′-O-(imidazol-1-ylcarbonyl)-3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)uridine, prepared from uridine, was treated with primary or secondary aliphatic amines to give 2′-carbamates in high yield. After 3′,5′-O-deprotection with triethylamine trihydrofluoride, 5′-O-dimethoxytritylation, and 3′-O-phosphitylation with bis(N,N-diisopropylamino)-2-cyanoethoxyphosphine, modified phosphoramidites were obtained and used in machine-assisted synthesis of modified oligodeoxynucleotides containing uridin-2′-yl carbamate residues bearing various N-substituents. The influence of uridin-2′-yl carbamate moieties on the stability of modified oligonucleotide duplexes with complementary DNA and RNA was studied by thermal denaturation experiments. Pyrene-modified oligonucleotides showed a considerable increase in fluorescence intensity upon hybridisation to complementary RNA and interesting binding properties when hybridised to a mismatched DNA.