Reaction of indoles with trifluoroacetic acid

3-Trifluoroacetyl indoles are formed by the action of trifluoroacetic acid on indole-2-carboxylic acid and its benzo-substituted derivatives. When unsubstituted indole is refluxed with trifluoroacetic acid, it gives 3-trifluoroacetylindole in 30% yield.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1233–1235, September, 1981.     

Reaction of para-substituted aromatic acids with methyl thiocyanate in trifluoroacetic acid

We have investigated the reactions of aromatic carboxylic acids (p-XC₆H₄COOH, in which X=F, Cl, Br, I, NO₂, CH₃, H, OCH₃) with methyl thiocyanate in trifluoroacetic acid. It was shown that the starting acids are converted to S-methyl benzothioates [p-XC₆H₄COSCH₃ (40–70%)] and the nitrile of the acid [p-XC₆H₄CN (20–50%)]. In addition to starting acid, in the reaction mixtures products of the reaction of CF₃COOH with methyl thiocyanate were identified.Institute of Oil and Gas Problems, Russian Academy of Sciences, I. M. Gubkin State Academy of Oil and Gas, 117917 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 412–416, February, 1992.     

A new type of acid-induced intramolecular cyclisation of Knoevenagel condensation products in the carbohydrate field. Stereochemical control of the cyclisation process.

The products of the Knoevenagel reaction between methyl acetoacetate and aldehydopentoses undergo various cyclisation processes when treated with trifluoroacetic acid in aprotic solvents which are controlled by the sugar configuration at C-2 and C-3.     

3-Oxocostusic acid fromArtemisia altaiensis

From the epigeal part ofArtemisia altaiensis Krash. we have isolated 3-oxocostus acid (selina-4,11(13)-dien-3-on-12-oic acid), the structure of the molecule of which has been confirmed by x-ray structural analysis, while its absolute configuration has been established from the results of circular dichroism.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 181–184, March–April, 1998.     

Trifluoroacetic acid in the synthesis of thiolcarbamates and s-methyl alkanethioates

The major products of the reaction of 2-bromohexanoic acid with methyl thiocyanate in trifluoroacetic acid are S-methyl 2-bromohexanethioate (II) (55% yield), S-methyl 2,2,2-trifluoroethanethioate (IV) (31% yield), N-trifluoro-acetyltrifluoroacetamide (V) (11% yield), and N-trifluoroacetyl-S-methylthiol-carbamate (III) (29% yield). N-2-Bromohexanoyl-S-methylthiolcarbamate (I), N-2-bromohexanoyltrifluoroacetaraide (VI), 2-thiapropioamide(VII), and S-methyl hex-anethioate (VIII) are also formed in minor amounts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 195–198, January, 1991.     

2-Cyanoacrylates in the conjugate addition of trifluoroacetic acid and nucleophilic reagents

In the presence of trifluoroacetic acid, ethyl 2-cyanoacrylate readily reacts with nucleophilic reagents, such as 2-chloro-1,3,2-benzodioxaphosphole, (EtO)₃P, (EtO)₂PCl, Ph₂PCl, Ph₃P, and thiourea. In these reactions the acid proton enters position 2 of the cyanoacrylate, whereas the nucleophilic component enters position 3, in accordance with the electron density distribution in the acrylate. In the absence of trifluoroacetic acid the above reagents, except 2-chloro-1,3,2-benzodioxaphosphole, cause ethyl 2-cyanoacrylate polymerization. The interaction of ethyl 2-cyanoacrylate with 2-chloro-1,3,2-benzodioxaphosphole and trifluoroacetic acid is the first example of a 2-cyanoacrylate taking part in the acid-initiated electrophilic conjugate addition of a weak nucleophile.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1245–1247, July, 1993.     

Transformations of 2α-hydroxy-2,6,6-trimethylbicyclo[3.1.1]-heptan-3-one under conditions of acid catalysis

The transformations of 2a-hydroxy-2,6,6-trimethylbicyclo[3.1.1]heptan-3-one under the conditions of acid catalysis have been studied. It has been shown that this compound can be used for the synthesis of products of various structures: a bridged bicyclic lactone (1,8,8-trimethyl-2-oxabicyclo[3.2.1]octan-3-one), an aromatic compound (carvacrol), and nitrogen-containing derivatives of p-menthane such as 8-acylamino-p-menth-6-en-2-ones. The structures of the compounds synthesized were shown by the results of¹H and¹³C NMR spectroscopies.Institute of Physical Organic Chemistry, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 35–42, January–February, 1990.     

Protic acid-induced intramolecular reactions of 2-cyclopropylazobenzenes

Treatment of 2-cyclopropylazobenzenes with concentrated sulfuric acid affords the intramolecular N- and C-alkylation products. Treatment of azobenzenes with trifluoroacetic acid results in quantitative rearrangement to arylindazoles via the intermediate formation of acid-stable indazolium ions. It is suggested that the formation of indazolium ions in trifluoroacetic acid results from the synchronous opening of the cyclopropane ring and stabilization of the developing carbocation by an internal nucleophile (the azo-group).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1063–1068, August, 1987.     

C-10 amino acid derivatives of colchicine

The synthesis has been effected of C-10 N-acylated amino acid derivatives of colchicine by condensing (-aminoethylamino) colchicide with N-acylated amino acids. The structures of the compounds obtained have been confirmed by their UV and PMR spectra and by thin-layer chromatography.M. A. Aidkhozhin Institute of Molecular Biology and Biochemistry, Kazakhstan Academy of Sciences, Alma-Ata. V. A. Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 372–375, May–August, 1992.     

NMR studies of 4(3H)-quinazolinones and 4(3H)-quinazolinethiones

Summary Unambiguous¹H and¹³C NMR assignments for 4(3H)-quinazolinones1–6 and their corresponding 4-thiones7–12 have been made. This resulted in the revision of the previous assignments for the two benzenoid carbons (C-5 and C-8) of quinazolinones1,2,4, and5. Thionation of the nucleophilic amides1–6 has been found to cause a distinct change in the¹³C chemical shift of particularly C-4, but also of those of C-4a, C-5, and C-8a. One-bond and several long range heteronuclear coupling constants for the compounds have also been measured.

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Kernresonanzspektroskopie von 4(3H)-Chinazolinonen und 4(3H)-Chinazolinthionen

Zusammenfassung Die¹H- und¹³C-NMR-Spektren der 4(3H)-Chinazolinone1–6 und ihrer entsprechenden 4-Thione7–12 wurden zugeordnet. Dabei zeigte sich, daß eine frühere Zuordnung der beiden benzoiden Kohlenstoffe (C-5 und C-8) der Chinazolinone1,2,4 und5 falsch war. Ersatz des Sauerstoffs durch Schwefel in den nukleophilen Amiden1–6 führt insbesondere für C-4, aber auch für C-4a, C-5 und C-8a zu einer deutlichen Änderung der chemischen Verschiebung. Heteronukleare Kopplungskonstanten über eine und über mehrere Bindungen wurden bestimmt.

     

Oxidation of fusidic acid

Summary 11-Oxofusidic acid — a previously unknown keto derivative of the antibiotic — has been isolated from the products of the oxidation of fusidic acid by chromium trioxide.All-Union Scientific-Research Institute of Antibiotics, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 66–69, January–February, 1979.     

Carbon-13 kinetic isotope effect of the decarbonylation of oxalic acid

Carbon-13 intramolecular kinetic isotope effects in the decarbonylation of oxalic acid dihydrate of natural isotopic composition by SO₃ and by fuming sulphuric acid at room temperature and decarbonylation of oxalic acid dihydrate by 100% H₃PO₄ in the temperature interval 80–150°C have been determined. The obtained isotopic and kinetic results have been compared with the earlier¹³C experimental and theoretical studies in other solvents.     

1H and13C NMR spectra of biologically active compounds. III. Diastereomers of (±)-7-thia- and 13-thia-16-aryloxy analogs of 11-deoxyprostaglandins of the E1 series

The structure has been established and stereochemical assignments have been made of two complete sets of diastereomers of the 7-thia and 13-thia analogs of 11-deoxy-prostaglandins of the E₁ series by the¹³C NMR method. It is proposed to determine the diastereomeric effects of the¹³C NMR chemical shifts, which are differential parameters bearing information on the stereochemistry of the molecules. Diagnostic diastereomeric effects have been found for assigning stereoisomers with respect to the C-15-hydroxy group and also with respect to the C-8 and C-12 chiral centers of the cyclopentane ring.Institute of Chemistry of the Bashkir Branch of the USSR Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 282–287, March–April, 1988.     

Carbon-13 kinetic isotope effects in the decarbonylation of lactic acid of natural isotopic composition in phosphoric acid medium

The¹³C kinetic isotope effect fractionation in the decarbonylation of lactic acid (LA) of natural isotopic composition by concentrated phosphpric acids (PA) and by 85% H₃PO₄ has been studied in the temperature interval of 60–150°C. The values of the¹³C₍₁₎ isotope effects in the decarbonylation of lactic acid in 100% H₃PO₄, in pyrophosphoric acid and in more concentrated phosphoric acids are intermediate between the values calculated assuming that the C₍₁₎–OH bond is broken in the rate-controllin gstep of dehydration and those calculated for rupture of the carbon-carbon bond in the transition state. In the temperature interval of 90–130°C the experimental¹³C fractionation factors determined in concentrated PA approach quite closely the¹³C fractionation corresponding to C₍₂₎–C₍₁₎ bond scission. the¹³C₍₁₎ kinetic isotope effects in the decarbonylation of LA in 85% orthophosphoric acid in the temperature range of 110–150°C coincide with the¹³C isotope effects calculated assuming that the frequency corresponding to the C₍₁₎–OH vibration is lost in the transition state of decarbonylation. A change of the mechanism of decarbonylation of LA in going from concentrated PA medium to 85% H₃PO₄ has been suggested. A possible secondary¹⁸O and a primary¹⁸O kinetic isotope effect in decarbonylation of lactic acid in phosphoric acids media have been discussed, too.     

Carbon-13 kinetic isotope effects in the decarbonylation of formic acid of natural isotopic composition in phosphoric acid media

The¹³C kinetic isotope effect (K.I.E.) in the decarbonylation of formic acid of natural isotopic composition in 85% orthophosphoric acid, in 100% H₃PO₄, and in pyrophosphoric acid has been measured in different temperature intervals ranging from 19 to 133 °C. In 85% H₃PO₄ the carbon-13 K.I.E. is determined by the fractionation of carbon isotopes expected for C–O bond rupture (k ₁₂/k ₁₃=1.0531 at 70°C). In 100% H₃PO₄ the¹³C K.I.E. indicates that C–H bond rupture is the major component of the reaction coordinate motion (thek ₁₂/k ₁₃ lay in the range of 1.026–1.017 over the range 30–70 °C). In pyrophosphoric acid the fractionation factor for¹³C equals 1.010 at 19 °C. Activation parameters for the decarbonylation of H¹²COOH in phosphoric acid media have been determined also and suggestions concerning the intimate mechanisms of decarbonylation of formic acid in dilute and concentrated phosphoric acids are made.     

Pyrroles from ketoximes and acetylene. 41. Some reactions of 1-vinyl-2-(2-furyl)- and-(2-thienyl)pyrroles

We have studied the reaction of 1-vinyl-2-(2-furyl)- and -(2-thienyl)pyrroles with trifluoroacetic anhydride, with hydrogen in the presence of catalysts (Raney nickel, palladium black, palladous chloride), with propargyl alcohol in electrophilic conditions [catalysis by perfluorobutyric acid in the system azoisobutyrodinitrile (AIBN)-CCl₄), and with alkane thiols with AIBN initiation. The products are novel substituted hetarylpyrroles.See [1] for Communication 40.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 337–342, March, 1991.     

Synthesis and isolation of monoesters of sucrose and arachidonic acid

Monoesters of sucrose and arachidonic acid have been synthesized by the transesterification of ethyl arachidonate with unprotected sucrose, and the structural isomers — 6-O-arachidonoylsucrose, 6-O-arachidonoylsucrose, and 3-O-arachidonoylsucrose — have been separated chromatographically. The positions of the ester bonds in these compounds were determined by the¹³C NMR method.All-Union Scientific-Research Institute of the Technology of Blood Substitutes and Hormone Preparations, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 499–502, July–August, 1988.     

New access to the synthetic building block -aspartic acid β-semialdehyde via Grignard reaction

A new, efficient, and inexpensive synthesis of protected -aspartic acid β-semialdehyde has been developed starting from -glutamic acid via a substituted -allylglycine derivative as intermediate. The key step of the reaction sequence was a strongly solvent-dependent Grignard reaction of an -glutamic acid semiester. The desired regioselective addition to the C-5 ester group was achieved in 1,2-dimethoxyethane while reactions in diethyl ether gave products resulting from additional attack at the carboxylic acid functionality.     

13C NMR spectra of biologically active compounds XI. Diastereomeric effects in C-glycosides

The¹³C NMR spectra of epimeric C-D-glucopyranosides with alkyl, aryl, and alkynyl substituents have been studied. The diastereomeric effects of the chemical shifts have been determined and assignments have been made to the 1-and 1- stereochemical series on the basis of HH COSY and CH HET CORR two-dimensional NMR spectra. The diastereomeric effects observed for the C-3 and C-5 carbon atoms are proposed as characteristic parameters for establishing the stereochemistry at the C-1 carbon atom.Institute of Chemistry, Bashir Scientific Center, Urals Branch, Academy of Sciences of the USSR, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 368–373, May–June, 1991.