Showing papers in "Heterocycles in 1991"
TL;DR: The syntheses and reactions of Meldrum's acid derivatives as well as their applications in natural product syntheses reported during 1978-1990 are reviewed in this paper, where the synthesis and reaction of acid derivatives are discussed.
Abstract: The syntheses and reactions of Meldrum's acid derivatives as well as their applications in natural product syntheses reported during 1978-1990 are reviewed
164 citations
TL;DR: In this article, a review dealing mainly with the prototropic side chain tautomerism of heteroaromatic compounds is presented, with particular reference made to molecular orbital calculations of equilibrium constants.
Abstract: This review deals mainly with the prototropic side chain tautomerism of heteroaromatic compounds. Particular reference is made to molecular orbital calculations of equilibrium constants
121 citations
TL;DR: Developments taken place in the field of artemisinin and related antimalarials during the last five years have been reviewed.
Abstract: Developments taken place in the field of artemisinin and related antimalarials during the last five years have been reviewed
86 citations
TL;DR: The structures, biological activities, and syntheses of marine natural products containing indole and dihydroindole nuclei are reviewed in this article, where the authors present a method to synthesize a marine natural product with indole.
Abstract: The structures, biological activities, and syntheses of marine natural products containing indole and dihydroindole nuclei are reviewed
59 citations
TL;DR: In this article, the electron acceptor properties of viologens, the outlines of porphyrin-viologen systems, complexes of VIs with donors and polymeric VIs are discussed.
Abstract: Pointing out electron acceptor properties of viologens, the outlines of porphyrin-viologen systems, complexes of viologens with donors and polymeric viologens are described along with biological interest of viologens
53 citations
TL;DR: The reaction of nitrile imines (II) with α-amino esters (III) proceeds with no detectable racemization and constitutes a convenient synthetic route to 4,5-dihydro-1,2,4-triazin-6-ones (IV).
Abstract: The reaction of nitrile imines (II) with α-amino esters (III) proceeds with no detectable racemization and constitutes a convenient synthetic route to 4,5-dihydro-1,2,4-triazin-6-ones (IV). Permanganate oxidation of the heterocycles (IV) affords the corresponding 1,2,4-triazin-6-ones (V). The reaction of (II) with β-amino esters gives the respective acyclic amidrazone adducts (VI)
50 citations
TL;DR: In this article, the selective functionalization of 2,2'-bithiophene molecule was described, which was achieved by sequential bromination of the 3,3' and 5,5' positions followed by debromination at the 5, 5' positions.
Abstract: The selective functionalization of the 2,2'-bithiophene molecule is described. Selective alkyl substitution at the 3,3' positions was achieved by sequential bromination of the 3,3' and 5,5' positions followed by debromination at the 5,5' positions. The resultant 3,3'-dibromo-2,2'-bithiophene was transformed via a Grignard reaction to give a series of 3,3'-dialkyl-2,2'-bithiophenes. Finally, nitration of the active 5,5' positons gave the corresponding 3,3'-dialkyl-5,5'-dinitro-2,2'-bithiophenes
49 citations
TL;DR: In this article, a series of oligo[thiophene-2,5-diyl]vinylenes (3) were synthesized by the carbonyl coupling of thiophene carbaldehydes with a low-valent titanium reagent.
Abstract: Preparation of a series of oligo[thiophene-2,5-diyl]vinylenes (3) is reported. Compounds containing an even number of thiophene rings were synthesized by the carbonyl coupling of thiophenecarbaldehydes with a low-valent titanium reagent and those carrying an odd number of thiophene rings by the coupling of thiophenecarbaldehydes with Wittig-Homer (Wittig) reagents. Uv-vis spectral feature of these compounds is also reported
46 citations
TL;DR: The structural elucidations of gigantetrocin and gigantriocin, two novel bioactive monotetrahydrofuran acetogenins with vicinyl hydroxyls are presented, showing good potential for in vivo antitumor activities.
Abstract: The structural elucidations of gigantetrocin and gigantriocin, two novel bioactive monotetrahydrofuran acetogenins with vicinyl hydroxyls are presented. These compounds are significantly and selectively cytotoxic to human tumor cells in culture and toxic to brine shrimp, and they inhibit the formation of crown gall tumors on potato discs, showing good potential for in vivo antitumor activities
45 citations
TL;DR: The structures, biological activities, and syntheses of marine, natural products containing quinoline and/or isoquinoline nuclei are reviewed in this paper, where the structure, biological activity and synthesisation of marine natural products with quinolines are discussed.
Abstract: The structures, biological activities, and syntheses of marine, natural products containing quinoline and/or isoquinoline nuclei are reviewed
43 citations
TL;DR: In this article, an easy handling method of 1-hydroxyindole is developed, and a new regioselective lithiation of 1methoxyindole and its application for the synthesis of 2-substituted indoles are also reported.
Abstract: An easy handling method of 1-hydroxyindole is developed. Based on the method, preparation and reaction of 1-hydroxyindole derivatives are investigated. A new regioselective lithiation of 1-methoxyindole and its application for the synthesis of 2-substituted indoles are also reported
TL;DR: In this article, two new phtalide dimers, senkyunolide O (1) and senkynolide P (2), along with three known phtalides dimers were isolated from the rhizome of Ligusticum chuangxiong Hort.
Abstract: Two new phtalide dimers, senkyunolide O (1) and senkyunolide P (2), along with three known phtalide dimers were isolated from the rhizome of Ligusticum chuangxiong Hort. On the basis of spectral analyses and chemical methods, the structure of these compounds were determined.
TL;DR: Citreochlorol (7), citreoisocoumarin (9), and citroisocoumorinol (12) have been isolated from the mycelia of Penicillium citreo-viride N. (IFO 4692) on addition of sodium bromide, and P. citreovirens (IO 6030), respectively as discussed by the authors.
Abstract: Citreochlorol (7), citreoisocoumarin (9), and citroisocoumarinol (12) have been isolated from the mycelia of Penicillium citreo-viride N. (IFO 4692), P. citreo-viride B. (IFO 4692) on addition of sodium bromide, and P. citreovirens (IFO 6030), respectively. Citroisocoumarin was tentatively assigned as 3-(2S-hydroxy-4-oxopentyl)-6,8-dihydroxyisocoumarin and citreoisocoumarinol was identified as 3-(2S,4S-dihydroxypentyl)-6,8-dihydroxyisocoumarin. Both of them are new members of the small group of naturally occuring isocoumarins. The structure of the new phenolic metabolite citreochlorol has also been established on the basis of spectral data analysis
TL;DR: Solid-liquid phase transfer catalysis (PTC) without added solvent efficiently promotes S N Ar reactions on halopyridines with a variety of anionic nucleophiles generated in situ as discussed by the authors.
Abstract: Solid-liquid phase transfer catalysis (PTC) without added solvent efficiently promotes S N Ar reactions on halopyridines with a variety of anionic nucleophiles generated in situ. This methodology gives access to substituted pyridines in very simplified conditions depending on halide nature. Mechanistic investigations are proposed
TL;DR: Using consecutive iron-induced C-C and C-N bond formation, the first total synthesis of carbazomycinal (carbazomycin E) was accomplished.
Abstract: Using consecutive iron-induced C-C and C-N bond formation the first total synthesis of carbazomycinal (carbazomycin E) was accomplished.
TL;DR: In this article, the 2,4-enyne moiety regio- and stereoselectively was introduced into the above heterocycles using this methodology, and a convenient procedure for introducing the 2.4-enzymethylsilyl-3-trimethyl silyloxy-4-ethylbenzo[b]furan derivatives in good yields.
Abstract: Dicobalt hexacarbonyl complexes of propargylium and α-vinylpropargylium cations couple efficiently with 2-trimethylsilyloxyfuran (5), 4-trimethylsilyloxy-2-benzyloxymethylfuran (15) and 2-trimethylsilyl-3-trimethylsilyloxy-4-ethylbenzo[b]furan (20) to produce the corresponding complexed furan derivatives in good yields. A convenient procedure for introducing the 2,4-enyne moiety regio- and stereoselectively into the above heterocycles using this methodology is described
TL;DR: By Wittig reaction of o-xylylenebis(triphenylphosphonium bromide) with aldehydes (2) and formaldehyde in the presence of base, unsymmetrically substituted o-divinylbenzenes (3) have been prepared in one pot as mentioned in this paper.
Abstract: By Wittig reaction of o-xylylenebis(triphenylphosphonium bromide) (1) with aldehydes (2) and formaldehyde in the presence of base, unsymmetrically substituted o-divinylbenzenes (3) have been prepared in one pot.
TL;DR: The asymmetric addition of methyl nucleophiles to homochiral N-acylisoquinolinium salts was studied and utilized in a synthesis of the tetrahydroisoquinoline alkaloid, (+)-carnegine as discussed by the authors.
Abstract: The asymmetric addition of methyl nucleophiles to homochiral N-acylisoquinolinium salts was studied and utilized in a synthesis of the tetrahydroisoquinoline alkaloid, (+)-carnegine
TL;DR: On the basis of previous studies on synthetic models related to the antibiotic agents Netropsin and Distamycin-A, the design and synthesis of two potential DNA minor groove ligands are described.
Abstract: On the basis of previous studies on synthetic models related to the antibiotic agents Netropsin and Distamycin-A, the design and synthesis of two potential DNA minor groove ligands are described. Methia-Nt and Isothia-Nt were prepared by liquid-phase peptidic synthesis from the key compounds ethyl 2-amino-5-methylthiazole-4-carboxylate (1) and ethyl 2-aminothiazole-5-carboxylate (8) respectively
TL;DR: In this paper, 2H-cyclohepta[b]furan-2-ones with orthoesters were synthesized in one-pot and in good yields.
Abstract: 2-Alkoxy and 2,4-dialkoxyazulene derivatives were synthesized in one-pot and in good yields by the reaction of 2H-cyclohepta[b]furan-2-ones with orthoesters on heating either neat or in an aprotic solvent at 160-190 o C
TL;DR: Refluxing of dipivaloylmethane in an excess of oxalyl chloride gives a mixture containing the 5-chloro-furanone derivatives (2), (3), and (4), which then can be completely converted into the 5tert-butyl-4-pivaloylfuran-2,3-dione (5) Compounds (2-5) are hydrolyzed to the carboxylic acid (6), which in reverse is easily recyclized to 5 as mentioned in this paper.
Abstract: Refluxing of dipivaloylmethane (1) in an excess of oxalyl chloride gives a mixture containing the 5-chloro-furanone derivatives (2), (3), and (4), which then can be completely converted into the 5-tert-butyl-4-pivaloylfuran-2,3-dione (5) Compounds (2-5) are hydrolyzed to the carboxylic acid (6), which in reverse is easily recyclized to 5
TL;DR: In this article, a Spectrophotometric evaluation of the UV-photoprotecting ability as compared to p-aminobenzoic acid (PABA) showed that the predicted effectiveness of 2 and 3-phenylisoxazoles (3B) is very close to that of PABA.
Abstract: Reaction of the acetylenic ketones (1) with hydrazine or hydroxylamine leads to the pyrazoles (2) or the isoxazoles (3), respectively. Spectrophotometric evaluation of the UV-photoprotecting ability as compared to p-aminobenzoic acid (PABA) shows that the predicted effectiveness of 2 and the 3-phenylisoxazoles (3B) is very close to that of PABA, while that of the 5-phenylisoxazoles (3A) is clearly lower. The pyrazoles (2) are more stable than PABA upon UV-irradiation in cyclohexane solution
TL;DR: In this article, the tautomeric equilibria of all these substrates by 13 C-nmr showed that thioether and nitrile exhibit the 2-quinolone structure.
Abstract: The reaction of ethyl N-[2-(2-Z-acetyl)phenyl] carbamates with Nah/THF yields 3-Z-2,4-dihydroxquinolines [Z-SMe, SOMe, SO 2 Me and CN]. The study of the tautomeric equilibria of all these substrates by 13 C-nmr shows that thioether and nitrile exhibit the 2-quinolone structure, whereas the sulfoxide and probably the sulfone exist as 4-quinolone tautomers
TL;DR: In this paper, the reaction of the title hydrazones with isoquinoline and quinoline, respectively, was shown to yield good yields for 2.2-Arylimidazo [2, 1-a] isoquinolines and -[1, 2-a]-quinolines.
Abstract: 2-Arylimidazo[2,1-a]isoquinolines and -[1,2-a]-quinolines were obtained in good to moderate yields by the reaction of the title hydrazones with isoquinoline and quinoline, respectively.
TL;DR: In this article, a good yield of 3-amino-5-tert-butylisoxazole (3) was obtained regioselectively from a reaction of 4,4-dimethyl-3-oxopentanenitrile (1) with hydroxylamine in the aqueous solution of which was adjusted to weak basic, followed by treatment of the resulting 4, 4-dimethyltetentaneamidoxime with hydrochloric acid
Abstract: A good yield of 3-amino-5-tert-butylisoxazole (3) was obtained regioselectively from a reaction of 4,4-dimethyl-3-oxopentanenitrile (1) with hydroxylamine in the aqueous solution of which was adjusted to weak basic, followed by treatment of the resulting 4,4-dimethyl-3-oxopentaneamidoxime (2) with hydrochloric acid
TL;DR: Two ring-expanded analogues (compouds 13 and 14) of the anti-HIV agents cyclobut-A and cyclobUT-G are described and neither compound was able to provide protection to CEM cells against HIV-1 infection.
Abstract: Two ring-expanded analogues (compouds 13 and 14)of the anti-HIV agents cyclobut-A and cyclobut-G are described. They were synthesized from trans-3,4-bis-(hydroxymethyl)cyclobutylamine which was obtained from threo-3,4-bis(methoxycarbonyl)-hexane dioic acid. Neither compound (13, 14) was able to provide protection to CEM cells against HIV-1 infection
TL;DR: The rhodium diacetate induced insertion reactions of some simples esters and amides of diazomalonic acid result in the formation of β-lactones and β -lactams as discussed by the authors.
Abstract: The rhodium diacetate induced insertion reactions of some simples esters and amides of diazomalonic acid result in the formation of β-lactones and β-lactams
TL;DR: In this paper, a novel isolate was obtained from an extract prepared from the seeds of Albizia amara, which was structurally defined as a mixture of three macrocyclic alkaloids of the pithecolobine type.
Abstract: On the basis of DNA affinity, a novel isolate was obtained from an extract prepared from the seeds of Albizia amara. As determined by a series of spectroscopic techniques, the isolate was structurally defined as a mixture of three macrocyclic alkaloids of the pithecolobine type that differed only in the length of the aliphatic side chain. The 1 H- and 13 C-nmr spectral parameters were unambiguously assigned to these alkaloids, which were given the trivial names budmunchiamine A, B or C. With the exception of former studies performed with Pithecolobium saman, this is the only other report of pithecolobine alkoids being found in nature
TL;DR: In this article, the same authors used 2.2 equivalents of lithium diisopropylamide to give 4,6-dilithiated thianthrene-5-oxides.
Abstract: Thianthrene-5-oxide (1) reacted with 2.2 equivalents of lithium diisopropylamide to give 4,6-dilithiated 1 which was converted to 4,6-disubstituted thianthrene-5-oxides (3). 3 afforded sterically crowded 1,9-disubstituted dibenzothiophenes (4) in moderate yields on treatment with n-butyllithium or phenyllithium