N-methyl Analogues Research Articles

Heteronuclear NMR studies of the chromone alkaloids and revision of the structure of some piperidino-chromone alkaloids.

The 13C-NMR spectra of seven chromone alkaloids isolated from Schumanniophyton magnificum have been obtained. Assignment of signals was carried out with the help of heteronuclear coupling experiments and other correlation techniques on the alkaloids and their acyl derivatives. On the basis of the signals observed the structures of the piperidino-alkaloid schumannificine and its N-methyl and anhydro analogues have been revised to that of a piperidone ring linked to the noreugenin via a carbon-carbon bond and a lactol bridge.

C-9 and N-substituted analogs of cis-(3aR)-(-)-2,3,3a,4,5,9b-hexahydro-3- propyl-1H-benz[e]indole-9-carboxamide: 5-HT1A receptor agonists with various degrees of metabolic stability.

Closely related analogs of the 5-HT1A receptor agonist cis-(3aR)-(-)-2,3,3a,4,5,9b-hexahydro-3-propyl-1H-benz[e]indole-9- carboxamide (1, U93385) were synthesized and pharmacologically evaluated. 9-Carboxamide analogs with varied nitrogen substitution (R2) were synthesized, and their serotonergic activity was evaluated in vitro and in vivo. Many of these compounds were incubated in the presence of rat hepatocytes, and the metabolic stability in vitro was compared to that of compound 1. Only the N-methyl and N-ethyl analogs ((-)-5a and (-)-5b) were more stable than compound 1, indicating that N-dealkylation is a major route of metabolism in this series. In addition, these analogs were found to be partial 5-HT1A receptor agonists in vivo. Modifications were also made to the carboxamide functionality of compound 1 (R1 in 2) to yield substituted amides or ketones. Among these analogs, the methyl ketone (-)-15a was found to be a 5-HT1A agonist with full intrinsic activity in vivo and was approximately 20 times more potent than compound 1 and 5 times more potent than 8-OH-DPAT.

Effect of the R(−) and S(+) isomers of MDA and MDMA on phosphotidyl inositol turnover in cultured cells expressing 5-HT 2A or 5-HT 2C receptors

The effect of the R(−) and S(+) isomers of 3,4-methylenedioxyamphetamine (MDA) and its N-methyl analog 3,4-methylenedioxymethamphetamine (MDMA) on [ 3H]inositol monophosphate accumulation was studied in cells expressing either 5-HT 2A or 5-HT 2C receptors. The isomers of MDA produced a concentration dependent increase in phosphotidyl inositol (PI) hydrolysis at the 5-HT 2A receptors, with the R(−) isomer of MDA being more potent than the S(+) at the 5-HT 2A receptor. The R(−) and S(+) isomers of MDMA were significantly less efficacious at the 5-HT 2A receptor as compared to MDA; S(+)MDMA had no effect. At the 5-HT 2C receptor, both R(−) and S(+)MDA were equipotent at stimulating PI hydrolysis, with the S(+) isomer of MDMA being more efficacious at the 5-HT 2C receptor compared with the R(−) isomer. In all cases at both the 5-HT 2A and 5-HT 2C receptors, the affinities of the isomers of MDMA and MDA were at least 2–3 orders of magnitude less than 5-HT. Despite the weak effect of these compounds at the 5-HT 2A and 5-HT 2C receptors, these substituted amphetamines do possess intrinsic activity which may contribute to their neurotoxic effects when administered at high doses.

Synthesis and properties of new cationic-periphery porphyrins, tetrakis(p-(aminomethyl)phenyl)porphyrin and N-methyltetrakis(p-(aminomethyl)phenyl)porphyrin

Two new cationic periphery porphyrins, tetrakis(p-(aminomethyl)phenyl)porphyrin, TAMPP, and N-methyltetrakis(p-(aminomethyl)phenyl)porphyrin, N-MTAMPP, have been synthesized. These porphyrins are protonated in a pH range suitable for studies of binding with nucleic acids. The structure of the N-methylated analogue is significantly different, resulting in a phenonmenon that has not been previously reported: the aryl rings at the methine bridge positions of the porphyrin ring undergo restricted rotational motion. The ability of the aryl rings to rotate may be crucial to allow intercalation of cationic periphery porphyrins. The acidity constants and associated pK a 's for the porphyrins TAMPP and N-MTAMPP were determined by a combination of spectrophotometric and potentiometric methods. The acid-base properties of these new porphyrins are profoundly altered by N-methylation. As a result, the N-methylated species bears an additional positive charge in the neutral pH region where binding studies with nucleic acids are normally carried out. The peripheral aminogroups of the N-methylated porphyrin are more basic as well, by 1.5 pH units at an ionic strength of 0.12 M

A Convenient Synthesis of 2-(diethoxyphosphonyl)glycine and its derivatives

A simple and very efficient method for the preparation of 2-(diethoxyphosphonyl)-glycine and its N-methyl analog as the free acids is described and their conversion to the corresponding t-butyl esters demonstrated.

Glycine transformation of Ca 2+ oscillations into a sustained increase parallels potentiation of insulin release

Increase of the glucose concentration from 3 to 11 mM resulted in a triphasic release of insulin from perifused ob/ ob-mouse β-cells. A slight inhibition was followed after 2 min by a marked peak and a less pronounced sustained response. At the lower glucose concentration glycine had only marginal effects. However, in the presence of 11 mM glucose, 1–10 mM glycine triggered an immediate and dose-dependent response with an initial peak of insulin release followed by sustained stimulation. In individual β-cells, rise of the glucose concentration from 3 to 11 mM induced initial lowering of the cytoplasmic Ca 2+ concentration ([Ca 2+] i) followed by large amplitude oscillations from a level of 50–90 nM to peak values exceeding 300 nM. Already at a concentration of 1 mM, glycine transformed the oscillatory pattern into a sustained level with increase of time-average [Ca 2+] i. This elevation became more pronounced in the presence of 10 mM glycine. The effects of glycine on insulin release and [Ca 2+] i required extracellular Na + and were reproduced with the N-methyl analogue sarcosine. It is suggested that glycine potentiation of secretion reflects the elevation of time-average [Ca 2+] i both by increased entry and reduced elimination of the cation from the cytoplasm.

N-methylated analogs of Ac[Nle28,31]CCK(26-33): synthesis, activity, and receptor selectivity.

A series of singularly N-methylated analogs of Ac[Nle28,31]CCK(26-33) were synthesized by the solid-phase methodology, and their biological activity was tested in three different in vitro bioassays. The bioassays employed were the guinea pig gallbladder (GPGB), stomach (GPS), and ileum (GPI). All N-methyl analogs were agonists in all three bioassays. N-Methylation at either N- or C-terminals did not affect potency and selectivity, whereas N-methylation of internal residues [Nle28,(N-Me)Nle31]- and [Nle28,31,(N-Me)Trp30]CCK(26-33) in the sequence resulted in analogs which were 10-fold less potent than Ac[Nle28,31]CCK(26-33) in all three preparations. Different rank orders of potencies observed for [Nle28,31,Sar29]- and [Nle28,31,(N-Me)Asp32]CCK(26-33) analogs correspond to increased selectivity to either GPGB or GPS, respectively. We propose that systematic N-methylation of single amide bonds in a bioactive peptide should be conducted as an additional routine to probe structure-activity relationships.

Aminoalkylbenzotriazoles: reagents for the aminoalkylation of electron rich heterocycles

Secondary and tertiary aminoalkylbenzotriazoles react with pyrrole, indole, their N-methyl analogs and with 2-methylfuran under mild reaction conditions in the presence of a Lewis acid to afford selectively the corresponding secondary or tertiary amines.

Formycins A and B and some analogues: selective inhibitors of bacterial (Escherichia coli) purine nucleoside phosphorylase.

Formycin B (FB), a moderate inhibitor (Ki approximately 100 microM) of mammalian purine nucleoside phosphorylase (PNP), and formycin A (FA), which is totally inactive vs. the mammalian enzyme, are both effective inhibitors of the bacterial (Escherichia coli) enzyme (Ki approximately 5 microM). Examination of a series of N-methyl analogues of FA and FB led to the finding that N(6)-methyl-FA, virtually inactive vs. the mammalian enzyme, is the most potent inhibitor of E. coli purine nucleoside phosphorylase (Ki approximately 0.3 uM) at neutral pH. Inhibition is competitive not only with respect to Ino, but also relative to 7-methyl-Guo and 7-methyl-Ado, as substrates. Both oxoformycins A and B are relatively poor inhibitors. For the most potent inhibitor, N(6)-methyl-FA, it was shown that the enzyme preferentially binds the neutral, and not the cationic, form. In accordance with this the neutral, but not the cationic form, of the structurally related N(1)-methyl-Ado was found to be an excellent substrate. Reported data on tautomerism of formycins were profited from, and extended, to infer which tautomeric species and ionic forms are the active inhibitors. A commercially available (Sigma) bacterial PNP, of unknown origin, was shown to differ from the E. coli enzyme by its inability to phosphorylase Ado; this enzyme was also resistant to FA and FB. These findings have been extended to provide a detailed comparison of the substrate/inhibitor properties of PNP from various microorganisms.

SYNTHESIS AND ANTICANCER SCREENING OF DIASTEREOISOMERIC 4,5-DIPHENYL- AND 3-METHYL-4,5-DIPHENYLCYCLOPHOSPHAMIDES

Abstract The four possible diastereoisomers of 4,5-diphenylcyclophosphamides (2–5) and their N-methyl analogues (6–9) have been synthesized via condensation of aminopropanols 10 and 11 (threo- and erythro) with bis-(2-chloroethyl)-phosphoramidic dichloride 12. Anticancer screening tests against L 1210 lymphoid leukaemia in mice did not show any therapeutic activity.

Mechanistic studies in the chemistry of thiourea. Part 3. Acid-catalysed reaction with 1-phenylpropane-1,2-dione and related compounds

Reaction of thiourea with 1-phenylpropane-1,2-dione in the presence of acid results in formation of 4,4′-methylenebis(5-phenyl-4-imidazoline-2-thione)11c. A mechanism of reaction is proposed, based on intermediates isolated from this and related reactions and on the detection of intermediates by 13C NMR spectroscopy using labelled reactants. With 1,3-dimethylthiourea the reaction ceases on formation of 1-(1,3-dimethyl-5-phenyl-2-thio-4-imidazolinyl)methyl-1,3-dimethylthiourea 4a and the analogue of this derived from thiourea is proposed as an intermediate in the formation of 11c. The two isomeric N-methyl analogues (11a and 11b) of 11c are obtained on reaction of 1-phenylpropane-1,2-dione with 1-methylthiourea. 1-Phenylbutane-1,2-dione and 1,3-diphenylpropane-1,2-dione react similarly, but 3-methyl-1-phenylbutane-1,2-dione does not react at all.

7-Aminoaziridinomitosenes: synthesis, structure, and chemistry

7-Aminoleucoaziridinomitosene (2a) has been proposed as a key intermediate in the reductive activation process for the antineoplastic agent, mitomycin C (1a). Little is known about 2a and its oxidized equivalent, 7-aminoaziridinomitosene (3a). An expedient electrochemical procedure for 3a and the corresponding N-methyl analogue 3b has been developed. NMR spectral studies of 3a in DMF-d 7 and DMSO-d 6 provided important information concerning the solution-state structure for this adduct. Factors controlling the aziridine ring-opening process under reductive and nonreductive conditions have been determined, as well as evidence for the intermediacy of 2a in the reductive activation cascade of 1a

Molecular structure of vecuronium bromide, a neuromuscular blocking agent. Crystal structure, molecular mechanics and NMR investigations

The crystal and molecular structure of vecuronium bromide {1-[2β,3α,5α,16β,17β)-3,17-bis(acetyloxy)-2-(piperidin-1-yl)androstan-16-yl]-1-methylpiperidinium bromide}, a potent non-depolarizing neuromuscular blocking agent, has been determined by single-crystal X-ray diffraction analysis. The compound crystallizes in the orthorhombic system, space group P212121. The observed axial conformation of the A ring acetoxy and piperidinyl substituents at positions 2 and 3 of the steroid skeleton is also present in solution, as is indicated by NMR experiments. After protonation of the piperidinyl group at position 2 this conformation changes into an equatorial conformation similar to the one observed in the N-methylated analogue pancuronium bromide. Molecular mechanics calculations have been performed to explain these observations.

C-nucleoside studies. Part 22. cine-Substitution in 1,4-dinitropyrazoles: further model studies, an improved synthesis of formycin and pyrazofurin and the synthesis of some 3(5)-alkylsulphonyl-4-amino-5(3)-β-D-ribofuranosylpyrazoles

Reaction of 3-methyl-1,4-dinitropyrazole 6 with ethyl 2-mercaptoacetate gave, by cine-substitution, ethyl [5(3)-methyl -4-nitropyrazol-3(5)-ylthio]acetate 8, which could be oxidised to the corresponding sulphoxide 11 or sulphone 12. Reduction and cyclisation of 8 and 12 gave respectively, 3-methyl-1,6-dihydropyrazolo[3,4-b]-1,4-thiazin-5(4H)-one 14 and the 5,7,7-trioxo analogue 15. Similarly treatment of 6 with glycine ethyl ester and sarcosine ethyl ester gave respectively ethyl 3(5)-methyl-4-nitropyrazol-5(3)-ylaminoacetate 16, and its N-methyl analogue 17; cyclisation of 17 gave 3,7-dimethyl-6,7-dihydro-1H-pyrazoeo[3,4-b] pyrazin-5(4H)-one 18. Reaction of 6 with various stabilized carbanions gave rise to a number of 3(5)-methyl-4-nitro-5(3)(2-oxoalkyl)pyrazoles.3(5)-(2,3,5-Tri-O-benzyl-β-D-ribofuranosyl)pyrazole 1 was subjected to transfer hydrogenation followed by acetylation, to give 1-acetyl-3-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)pyrazole 23 in 95% yield. Treatment of 23 with ammonium nitrate and trifluoroacetic anhydride in trifluoroacetic acid gave 1,4-dinitro-3-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)pyrazole 2(95%). This sequence gives a much improved route to formycin 4 and pyrazofurin 5 as compared to the previously-reported route involving 1 and 2 as intermediates. cine-Substitution of 2 with sulphur nucleophiles, and subsequent manipulation led to the synthesis of 4-amino-3(5)-methylsulphonyl-5(3)-(β-D-ribofuranosyl)pyrazole 29 and 4-amino-3(5)-[(carbamoyl)methyl] sulphonyl-5(3)-(β-D-ribofuranosyl)pyrazole 33.

The Determination of Chirality of N-Methyl- and N,N-Dimethyl-phenylalanine by G.L.C.

The chirality of N- methylphenylalanine enantiomers can be determined on a micro scale by g.l.c . of N-pentafluoropropionyl amino acid isopropyl esters on a Chirasil -L-Val capillary column. N,N- Dimethylphenylalanine enantiomers cannot be similarly derivatized and cannot be separated. However, prior treatment with ethyl chloroformate followed by acid hydrolysis effects demethylation to the N-methyl analogues which can then be derivatized for g.l.c . Contrary to literature reports N-methylphenylalanine can be prepared by reductive alkylation of phenylalanine.

Effects of alanine on insulin-secreting cells: Patch-clamp and single cell intracellular Ca 2+ measurements

The effects of alanine, glucose and tolbutamide on insulin-secreting cells (RINm5F) have been investigated using patch-clamp and single cell intracellular Ca 2+ measurements. When directly challenged with the amino acid l-alanine (2–10 mM) the cells underwent a sharp depolarization, which led to the generation of Ca 2+ spike potentials and an increase in [Ca 2+] i. The l-alanine-induced depolarization was associated with a net inward membrane current but no measurable change in the resistance of the cell. The latter effect was found to be in contrast to the actions of glucose (5–10 mM) and tolbutamide (100 μM), both of which depolarized cells and raised [Ca 2+] i by an increase in the input resistance of the cell membrane, due to the closure of ATP-sensitive potassium channels. In the complete absence of external Na + (by replacement with 140 mM NMDG +), l-alanine had no effects on either the membrane potential or [Ca 2+] i. Similarly, replacing Na + with NMDG + in the continued presence of the amino acid resulted in a repolarization of the membrane and an attenuation of the l-alanine-induced rise in [Ca 2+] i. The Na + channel blocker TTX (1–2 μM) had no effects on the alanine-evoked electrical activity. Exchange of the L-form of the amino acid with the d-stereoisomer had similar actions to those of removing external Na +, since d-alanine had no effects on the membrane potential or [Ca 2+] i. The actions of l-alanine were also found to be mimicked by the N-methylated amino acid analogue methylamino isobutyric acid (MeAIB) (2–10 mM), suggesting that the A-type electrogenic amino acid cotransport system operates in the RINm5F insulin-secreting cell line.

S-[2-[(2'-carbamoylethyl)amino]ethyl] phosphorothioate and related compounds as potential antiradiation agents

A reinvestigation of the radiation protection activity of S-[2-[(2'-carbamylethyl)amino]ethyl] lithium hydrogen phosphorothioate (4a) revealed that this compound possessed good (70% protection at a dose of 600 mg/kg) activity. The thione and imino bioisosteres of 4, S-[2-(2'-thiocarbamylethylamino)ethyl] lithium hydrogen phosphorothioate (13a) and S-[2-(2'-amidinoethylamino)ethyl] phosphorothioic acid (18b) showed 100% protection at doses of 300 and 150 mg/kg, respectively. The N-methyl (4b) and tert-butyl (4c) analogues of amide 4a, the N-methyl (13b) analogue of the thioamide 13a, the N-methyl (18a) analogue of amidine (18b), and the cyclic amidine S-[2-[[2'-(4,5-dihydroimidozoyl)ethyl]amino]ethyl] lithium hydrogen phosphorothioate (21) all showed 80% protection at the highest dose tested.

Synthesis and anticonvulsant activity of 2-benzylglutarimides

A series of 2-benzylglutarimides (4) and their N-methyl analogues (5) were prepared according to the Topliss scheme for the selection of benzyl substituents to maximize anticonvulsant activity. A total of 22 such compounds were subjected to initial (phase I) screening in mice against seizures induced by maximal electroshock (MES) and pentylenetetrazol (scMet) and in the rotorod assay for neurotoxicity. From this series of test compounds, 10 were advanced to quantitative (phase II) testing. Of these, 2-(4-chlorobenzyl)glutarimide (4b) emerged as the most promising anticonvulsant drug candidate by demonstrating both good anti-scMet and anti-MES activity combined with low neurotoxicity after intraperitoneal administration in mice. In drug differentiation tests, 4b was also effective in nontoxic doses against seizures induced by bicuculline, picrotoxin, and strychnine. When compared with the clinically useful drugs phenytoin, carbamazepine, phenobarbital, valproate, and ethosuximide, 4b exhibited an overall pharmacological profile most closely resembling that of valproate.

Synthesis and biological activity of an acyclic analog of 5,6,7,8-tetrahydrofolic acid, N-[4-[[3-(2,4-diamino-1,6-dihydro-6-oxo-5-pyrimidinyl)propyl]amino]benzoyl]-L-glutamic acid

The synthesis and biological evaluation of N-[4-[[3-(2,4-diamino-1,6-dihydro-6-oxo-5-pyrimidinyl)propyl]amino]- benzoyl]-L-glutamic acid (1) (5-DACTHF, 543U76), an acyclic analogue of 5,6,7,8-tetrahydrofolic acid (THFA), are described. The key intermediate, hemiaminal 8, was prepared in four stages from 3-chloropropionaldehyde diethyl acetal. Reaction of 8 with dimethyl N-(4-aminobenzoyl)-L-glutamate gave the 2,4-bis(acetylamino) derivative 11, which was hydrolyzed with 1 N sodium hydroxide to give 1; the glycine analogue 16 was prepared in a similar manner. The N-methyl analogue 2 and N-formyl analogue 3 were prepared from 11 and 1, respectively. Compounds 1-3 inhibited growth of Detroit 98 and L cells in cell culture, with IC50s ranging from 2 to 0.018 microM. Cell culture toxicity reversal studies and enzyme inhibition tests showed that 1 was cytotoxic but not by the mechanism of the dihydrofolate reductase inhibitor aminopterin. Compound 1 and its polyglutamylated homologues inhibited glycinamide ribonucleotide transformylase (GAR-TFase) and aminoimidazole ribonucleotide transformylase (AICAR-TFase), the folate-dependent enzymes in de novo purine biosynthesis; and 1 was an effective substrate for mammalian folyl-polyglutamate synthetase. The compound inhibited (IC50 = 20 nM) the conversion of [14C]formate to [14C]-formylglycinamide ribonucleotide by MOLT-4 cells in culture. These data suggest that the site of action of 1 is inhibition of purine de novo biosynthesis. Moderate activity was observed against P388 leukemia in vivo.

ChemInform Abstract: Preparation of Thieno(3,2‐e)(1,2)oxazepine, Thieno‐ and (1)Benzothieno‐(3,2‐g)(1,4)oxazonine, and 5H‐Thieno‐ and 1H‐(1)Benzothieno(3,2‐h)(1,5)oxazecine Derivatives by Ring Expansion Methods. X‐Ray Crystal Structure of 1‐Phenyl‐1,3,4,5,6,7‐hexahydro(1)benzothieno(3,2‐g)(1,4)oxazonine‐5‐carbonitrile.

10-Phenyl-4,5,6,7,8,10-hexahydrothieno[3,2-g][1,4]oxazonine-6-carbonitrile (6a) and 11-phenyl-4,6,7,8,9,11-hexahydro-5H-thieno[3,2-h][1,5]oxazecine-6-carbonitrile (7a) were prepared in moderate yields by cyanogen bromide-induced ring expansion of tetrahydrothieno [2,3- c] pyridinylalkanol precursors (4a) and (5a), respectively. 1-Phenyl-1,3,4,5,6,7-hexahydro[1]- benzothieno [3,2-g][1,4]oxazonine-5-carbonitrile (6b) and 1-phenyl-3,4,5,6,7,8-hexahydro-1H- [1] benzothieno [3,2-h][1,5]oxazecine-6-carbonitrie (7b) were similarly prepared from the [1] benzothieno [2,3-c] pyridinylalkanol precursors (4b) and (5b). The medium-ring cyanamides (6b) and (7b) were converted by standard methods into their N-methyl analogues (8b) and (9b). 6-Methyl-8-phenyl-4,5,6,8-tetrahydrothieno[3,2-e][1,2] oxazepine (13) was prepared by thermal Meisenheimer rearrangement of the corresponding tertiary amine N-oxide (12). The compounds (6a, b), (7a, b) and (13) are each the first reported examples of new heterocyclic systems. The crystal and molecular structure of (6b) has been determined by X-ray crystallographic methods.