Syntheses of 4-, 5-, 6-, and 7-substituted tryptamine derivatives and the use of a bromine atom as a protecting group

Orthogonal syntheses of 4-, 5-, 6-, and 7-chloro substituted tryptamine derivatives were performed under the Grandberg–Zuyanova-modified Fisher indole-synthesis conditions. In the 4- and 6-substituted tryptamine cases, a bromine atom was utilized as an easily cleavable protecting group, which allowed complete regiocontrol. In addition, a chlorine substituent was preserved in the debromination step and could be utilized as a synthetic handle for late-stage diversification under modern Pd(0) catalysis conditions.     

Negative-ion mass spectra of diterpene alkaloids with the keto group in the 6- or 7-position

Processes resulting in the formation of negative ions by molecules of some diterpene alkaloids via resonance electron capture have been studied. The mass spectra of these compounds have a small number of lines represented largely by intense peaks in the thermal electron energy region and are due to electron capture onto the lower unoccupied molecular orbital, which is π*-C=O or π*-Ph-C=O in character.     

Electrophilic substitution of thetert-butyl-NNO-azoxy group by the bromine atom

The electrophilic substitution of thetert-butyl-NNO-azoxy group by the bromine atom was observed for the first time when 6-bromo-2,4-bis(tert-butyl-NNO-azoxy)-5-chloro-1,3-phenylenediamine was treated with bromine in AcOH. The structural factors promoting this reaction are discussed. The direction of the replacement was confirmed by PM3 calculations of the heats of formation of intermediate cationic σ-adducts. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2131–2134, November, 1999.     

Synthesis and antitumor activity of lipid A analogs having a phosphonooxyethyl group with alpha- or beta-configuration at position 1

Three novel lipid A analogs, which have an alpha- or beta-glycosidically bound phosphonooxyethyl group instead of the alpha-glycosyl phosphate group of natural lipid A, were synthesized. The first analog (2) had an alpha-phosphonooxyethyl group on the identical acylated disaccharide 4'-phosphate structure found in natural lipid A (from Escherichia coli) and hence differed from the latter only in the nature of the acidic group at position 1. The second one (3) had tetradecanoyl groups in place of the two (R)-3-hydroxytetradecanoyl groups bound to the 2- and 3-hydroxyl function of 2, retaining the alpha-phosphonooxyethyl group. The structure of the third analog (4) was the same as that of 3 except that the phosphonooxyethyl group of the former was beta-oriented. Compounds 2 and 3 exhibited potent activity against Meth A at the same level as natural lipid A, whereas 4 showed less activity. This fact revealed that the glycosidic phosphate is not a prerequisite for the antitumor activity of lipopolysaccharide. It can be replaced with a phosphonooxyethyl group without any loss of activity provided that the alpha-anomeric configuration at C-1 is retained. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups does not change the activity either.     

Theoretical and experimental studies on the thermal ring-opening reaction of cyclobutene having a stannyl substituent at the 3-position

The ring-opening reaction of 3-(trimethylstannyl)cyclobutene gave a mixture of the (Z)- and (E)-1,3-dienes, whereas that of 3-tert-butylcyclobutene exclusively afforded the (E)-1,3-diene due to the steric influences. The contrasting rotational behaviors suggest that there is some effect operating with the 3-stannylcyclobutene to stabilize the inward transition state, counteracting the steric influences. This contrasteric effect is ascribed to negative hyperconjugation. The stannyl group in the inward transition state accommodates electron density from the breaking sigma orbital of the cyclobutene into its low-lying tin-carbon sigma orbital. Theoretical studies supported this interpretation.     

Quantum-chemical analysis of the nucleophilic substitution of the bromine atom by the cyano group at the sp-hybridized carbon atom in the methylbromoacetylene molecule

This paper reports on our quantum-chemical analysis of the nucleophilic substitution of the bromine atom by the cyano group in the reaction of methylbromoacetylene with copper cyanide. According to calculations, the reaction can form a four-membered ring containing a copper atom.     

Synthesis and properties of conformationally rigid cyclouridylic acid having a covalent bonding linker between the uracil 5-position and the 5′-phosphate group

A novel cyclouridylic acid 1 having a propylene bridge between the uracil 5 position and the 5′-phosphate group was synthesized. The structure of 1 was analyzed by ¹H NMR, and CD spectroscopy, which suggested that the cyclonucleotide 1 was highly stabilized in a considerably rigid g⁺/C3′-endo conformation with the base orientation of anti. The molecular mechanics calculation of 1 gave a similar conclusion.     

Synthesis of halosulfuron-methyl via selective chlorination at 3- and/or 5-position of pyrazole-4-carboxylates

Reactions of methyl pyrazole-4-carboxylates 4b-d with N-chlorosuccinimide under heating conditions without a solvent gave methyl 3,5-dichloro-1-methylpyrazole-4-carboxylate 4a in good yields. The reaction of 4a with sodium hydrosulfide led to a nucleophilic substitution on the 5-position regioselectively to afford methyl 3-chloro-1-methyl-5-mercaptopyrazole-4-carboxylate 6a, which was followed by oxidative chlorination and amination to obtain 3-chloro-1-methyl-5-sulfamoylpyrazole-4-carboxylate 2a. Finally, the reaction of 2a with phenyl 4,6-dimethoxypyrimidin-2-yl carbamate 7 provided methyl 3-chloro-5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylate (halosulfuron-methyl) 1a promising herbicide in com.     

Pulse radiolysis studies of the reactions of bromine atoms and dimethyl sulfoxide–bromine atom complexes with alcohols

Dimethylsulfoxide (DMSO)–Br complexes were generated by pulse radiolysis of DMSO/bromomethane mixtures and the formation mechanism and spectral characteristics of the formed complexes were investigated in detail. The rate constant for the reaction of bromine atoms with DMSO and the extinction coefficient of the complex were obtained to be 4.6×10⁹ M⁻¹ s⁻¹ and 6300 M⁻¹ cm⁻¹ at the absorption maximum of 430 nm. Rate constants for the reaction of bromine atoms with a series of alcohols were determined in CBrCl₃ solutions applying a competitive kinetic method using the DMSO–Br complex as the reference system. The obtained rate constants were ∼10⁸ M⁻¹ s⁻¹, one or two orders larger than those reported for highly polar solvents. Rate constants of DMSO–Br complexes with alcohols were determined to be ∼ 10⁷ M⁻¹ s⁻¹. A comparison of the reactivities of Br atoms and DMSO–Br complexes with those of chlorine atoms and chlorine atom complexes which are ascribed to hydrogen abstracting reactants strongly indicates that hydrogen abstraction from alcohols is not the rate determining step in the case of Br atoms and DMSO–Br complexes.     

Stereoselective synthesis of insect sex pheromone analogs having a fluorine atom on their double bonds

Insect sex pheromone analogs having a fluorine atom on their double bonds, (9E,11E)-1-acetoxy-9-fluorotetradecadiene, (10E,12E)-13-fluorohexadecadien-1-ol, (9Z,11E)-1-acetoxy-9-fluorotetradecadiene, (10E,12Z)-13-fluorohexadecadien-1-ol were stereoselectively synthesized using cross-coupling reactions of alkenylboranes with (E)- or (Z)-2-fluoro-1-iodo-1-alkenes, stereoselectively prepared from 1-alkynes by our currently developed methods.     

3- and 4-aminocyclohexanecarboxylic acids,containing either the diethylenimidophosphoryl or the diethylimidothiophosphoryl group

Conclusions We were the first to obtain the ethyl esters of the N-dichlorophosphoryl-3(and 4)-aminocyclohexanecarboxylic acids, the ethyl esters of the N-dichlorothiophosphoryl-3(and 4)-aminocyclohexanecarboxylic acids, the ethyl esters of the N-diethylenimidophosphoryl-3(and 4)-aminocyclohexanecarboxylic acids, the ethyl esters of the N-diethylenimidothiophosphoryl-3(and 4)-aminocyclohexanecarboxylic acids, the sodium salts of the N-diethylenimidophosphoryl-3(and 4)-aminocyclohexanecarboxylic acids, and the sodium salts of the N-diethylenimidothiophosphoryl-3(and 4)-aminocyclohexanecarboxylic acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 933–935, April, 1974.     

Transformations of hydroxyalkyl esters of thiophosphonic acids containing a phenoxy or dialkylamido group at the phosphorus atom

Conclusions The tendency toward cyclization with the loss of phenol or dialkylamine and formation of compounds with a 1, 3, 3-thiaoxaphosphorinane ring decreases in the series of 3-hydroxyalkyl esters of diphenythiophosphoric, alkyl-O-phenylthiophosphonic, phenyl-O-phenylthiophosphonic, and alkyldialkylamidothiophosphonic acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1197–1200, May, 1985.     

Preparation and reactions of mono-reissert compounds and analogs at the 3,4-position of quinazoline

Quinazoline, acid chlorides, and trimethylsilyl cyanide have been converted to mono-Reissert compounds at the 3,4-position of the quinazoline system. Various reactions of these quinazoline Reissert compounds are reported.     

Synthesis of Spirobenzopyrans Carrying a Monoaza-benzo-15-C-5 at the 8-position

SpirobenzopyranderivativesarewellknownphotochroAncorganiccompounds,whichcanbereversiblyisomerizedbyUVandvisiblelightirradiation.Whencrownmoietiesareincorporatedtothespirobenzopyrans,theymayprovidespirobenzopyranderivativeswithspecificcationbindingabilities,whichcaninduceisomerizationofthespirobenzopyrans,thusdrasticallyaffectingtheisomerizationequilibriumbetweenthespiropyranandthemerocycanineforms.Thesecrownedspirobenzopyranderivativesaremoreeffectiveforphotochemicalcontrolofphysicalpropertie…