Showing papers in "Molecules in 2002"
TL;DR: The main data mining approaches used in cheminformatics, such as descriptor computations, structural similarity matrices, and classification algorithms, are outlined in this paper, and future directions of chemoinformatics are suggested.
Abstract: This article reviews current achievements in the field of chemoinformatics and their impact on modern drug discovery processes. The main data mining approaches used in cheminformatics, such as descriptor computations, structural similarity matrices, and classification algorithms, are outlined. The applications of cheminformatics in drug discovery, such as compound selection, virtual library generation, virtual high throughput screening, HTS data mining, and in silico ADMET are discussed. At the conclusion, future directions of chemoinformatics are suggested.
179 citations
TL;DR: In this paper, a number of chalcones were prepared by condensing either 1-acetylnaphthalene or substituted naphthalenes with 1-naphthaldehyde or 4-dimethylamino-1-nophthaldehyde in ethanolic NaOH solutions, which were immediately reacted with hydrazine hydrochloride, phenyl hydrazines and semicarbazide hydrochlorides in the presence of dry acetic acid to obtain the corresponding 2-pyrazolines.
Abstract: A number of chalcones were prepared by condensing either 1-acetylnaphthalene or substituted 1-acetylnaphthalenes with 1-naphthaldehyde or 4-dimethylamino-1-naphthaldehyde in ethanolic NaOH solutions. These chalcones were immediately reacted with hydrazine hydrochloride, phenyl hydrazine and semicarbazide hydrochloride in the presence of dry acetic acid to obtain the corresponding 2-pyrazolines. The synthesised heterocycles were characterized on the basis of their chemical properties and spectroscopic data. These compounds were tested for antimicrobial activity against a variety of test organisms: Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Proteus mirabillis, Shigella dysentry and Salmonella typhii. The compounds containing chloro, hydroxo and dimethylamino - N(CH3)2 group as substituents on the naphthalene rings have been found to be very effective antimicrobial agents. In addition, the presence of a carboxamido -CONH2 substituent group at the N-1 position of the 2-pyrazoline rings is shown to contribute substantially to the antimicrobial activity.
142 citations
TL;DR: Only a tetrameric derivative of caffeic acid was isolated from P. japonicus, but a group of long-chain alkylphenols, of possible taxonomic significance in the genus, was also isolated.
Abstract: This review presents the phytochemical constituents of the genus Plectranthus reported up to 1999. Only a tetrameric derivative of caffeic acid was isolated from P. japonicus, but a group of long-chain alkylphenols, of possible taxonomic significance in the genus, was also isolated. As a genus of the subfamily Nepetoideae, Plectranthus is free from iridoid glycosides and rich in essential oil (i.e. > 0.5% volatile oil on a dry weight basis). Diterpenoids are the more common secondary metabolites in Plectranthus. The majority of them are highly modified abietanoids. This seems to be similar to the pattern of diterpenoids observed for Salvia, but no clerodane diterpenoids were found in Plectranthus.
134 citations
TL;DR: Three possible VS scenarios with respect to optimising binding affinity and pharmacokinetic properties are discussed and the parsimony principle for selecting candidate leads for further optimisation is advocated.
Abstract: Virtual screening (VS) methods have emerged as an adaptive response to massive throughput synthesis and screening technologies. Based on the structure-permeability paradigm, the Lipinski rule of five has become a standard property filtering protocol for VS. Three possible VS scenarios with respect to optimising binding affinity and pharmacokinetic properties are discussed. The parsimony principle for selecting candidate leads for further optimisation is advocated.
101 citations
TL;DR: It is concluded that strong intramolecular N-H----O bonds in the favoured keto-enamine form may be responsible for the minimal biological activities observed in DNA footprinting,Anti-tubercular, anti-fungal and anticancer tests with these hyper π-conjugated quinoxaline derivatives.
Abstract: A variety of 2,3-bifunctionalized quinoxalines (6-14) have been prepared by the condensation of 1,6-disubstituted-hexan-1,3,4,6-tetraones (1-4) with o-phenylenediamine, (R,R)-1,2-diaminocyclohexane and p-nitro-o-phenylenediamine. It is concluded that strong intramolecular N-H----O bonds in the favoured keto-enamine form may be responsible for the minimal biological activities observed in DNA footprinting, antitubercular, anti-fungal and anticancer tests with these hyper π-conjugated quinoxaline derivatives. However, subtle alteration by addition of a nitro group affecting the charge distribution confers significant improvements in biological effects and binding to DNA.
89 citations
TL;DR: In this article, the synthesis and spectroscopic characterisation of representative N-alkylsubstituted quaternary ammonium salts derived from benzothiazole, benzoxazoles, benzoselenazole, indole and quinoline are described.
Abstract: The synthesis and spectroscopic characterisation of some representative N-alkylsubstituted quaternary ammonium salts derived from benzothiazole, benzoxazole, benzoselenazole, indole and quinoline are described. These heterocyclic salts, bearing an activated methyl group in the 2-position in relation to the nitrogen atom and N-methyl, -pentyl, -hexyl and -decyl chains, are typical precursors of cyanine dyes.
79 citations
TL;DR: In this paper, the authors proposed a reduction in the amount of sulfuric acid needed and/or any simplification in handling procedures, which would be highly convenient in terms of risk reduction, economic advantages and environment protection.
Abstract: Nitrophenols can be obtained in moderate to high yields via nitrosation-oxidation of phenols with silica sulfuric acid, NaNO 2 and wet SiO 2 at room temperature. In situ generation of HNO 2 and a radical cation mechanism via the nitrous acid catalyzed (NAC) pathway appear to be applicable to phenol nitration using these reagents. Keywords: Silica sulfuric acid, nitrosation-oxidation, nitration, nitrophenols. Introduction In several industrially important processes ( e.g. nitration , nitrosation, etc.) a large excess of sulfuric acid is required because the water by-product slows the reaction down by diluting the acid. At the end of these processes, a large amount of “spent acid” is obtained which, in batch reactions, is usually neutralized and disposed of, while, in continuous processes, it has to be recycled by complex techniques. Also, the separation of the products from the acid is often a difficult and energy consuming process that habitually implies a basic aqueous work-up. Moreover, sulfuric acid is corrosive and is dangerous to transport and handle. Consequently, any reduction in the amount of sulfuric acid needed and/or any simplification in handling procedures would be highly convenient in terms of risk reduction, economic advantages and environment protection [1]. On the other hand, there is intense current research and general interest in heterogeneous systems because of the perceived opportunities
73 citations
TL;DR: In this paper, three optically active Schiff-base ligands have been prepared by condensation of 2-hydroxyacetophenone with (1R,2R)-(-)-1,2-diaminocyclohexane, (1S,2S)-(-]-1, 2-diphenylethylenediamine or R-(+)-2,2’diamino-1,1’-binaphthalene, respectively.
Abstract: Three optically active Schiff-base ligands have been prepared by condensation of 2-hydroxyacetophenone with (1R,2R)-(-)-1,2-diaminocyclohexane, (1S,2S)-(-)-1,2-diphenylethylenediamine or R-(+)-2,2’-diamino-1,1’-binaphthalene, respectively. The products have been characterized by their IR, 1H- and 13C-NMR spectra.
69 citations
TL;DR: The accumulation of isoflavonoid phytoalexins was studied in several Colombian bean cultivars resistant and susceptible to Colletotrichum lindemuthianum fungus, the causal agent of anthrachnose disease.
Abstract: The accumulation of isoflavonoid phytoalexins was studied in several Colombian bean cultivars resistant and susceptible to Colletotrichum lindemuthianum fungus, the causal agent of anthrachnose disease. A time-course accumulation analysis on seedlings treated with CuCl2 showed that phaseollin production was higher in resistant cultivars than in susceptible ones. Also, a defensive role of phytoalexins was demostrated when extracts containing this pterocarpan exhibited antifungal activity against C. lindemuthianum. In addition, the elicitor activity of some aminosugars was also established.
56 citations
TL;DR: In this paper, the assignment of all 1H- and 13C-NMR resonances of the isomers due to restricted C-N amide bond rotation of N-formyl-o-toluidine and N,N'-bis-formed formyl-of-tolidine in DMSO-d6 is reported.
Abstract: Full and unambiguous assignment of all 1H- and 13C-NMR resonances of the isomers due to restricted C-N amide bond rotation of N-formyl-o-toluidine and N,N'-bis-formyl-o-tolidine in DMSO-d6 is reported. The cis-isomer predominates in the equilibrium mixture of both compounds as 1D-NOE difference experiments show.
48 citations
TL;DR: An acylated kaempferol glycoside, namely kaempfol-3-O-α-L-(2fl,3fi-di-E -p -coumaroyl)-rhamnoside (1 ) was isolated from the flowers of Foeniculum vulgare mill.
Abstract: An acylated kaempferol glycoside, namely kaempferol-3-O-α-L-(2fl,3fl-di- E - p -coumaroyl)-rhamnoside ( 1 ) was isolated from the flowers of Foeniculum vulgare Mill. and F. dulce DC . It is thus isolated for the first time from family Apiaceae. In addition, the different organs of both plants afforded six flavonoid glycosides - namely afzelin (kaempferol-3-O-α-L-rhamnoside) ( 2 ), quercitrin ( 3 ), isorhamnetin-3-O-β-D-glucoside ( 4 ), isoquercitrin ( 5 ), rutin ( 6 ), and miquelianin (quercetin-3-O-β-D-glucuronide) ( 7 ). Structure elucidation of the above mentioned flavonoids was achieved by UV, 1 H- and 13 C-NMR, 1 H- 1 H COSY, HMQC and EI-MS. Keywords . Foeniculum vulgare , F. dulce , acylated kaempferol glycoside, spectroscopy. Introduction Foeniculum vulgare Mill. is used in folk medicine as carminative, digestive, lactagogue and diuretic. The leaves, stalks and fruits are edible [1, 2]. F. dulce DC. is an annual herb grown especially for its bulb-like swollen leaf bases which are delicious in salads [3, 4]. Flavonoids are more common throughout the family Apiaceae than other constituents [5]. The presence of flavonol glycoside types
TL;DR: In this article, a series of amides were tested for their in vitro antimycobacterial, antifungal and photosynthesis-inhibiting activities, including 6-chloro-, 5-tert-butyl-6-chloropyrazine-2-carboxylic acid (2o), 3-methylphenyl amides (3,5-bis-trifluoromethylphenyl)amide (2m, IC50 = 0.063 mmol·dm-3).
Abstract: Condensation of 6-chloro-, 5-tert-butyl- or 6-chloro-5-tert-butylpyrazine-2-carboxylic acid chloride with ring substituted anilines yielded a series of amides, which were tested for their in vitro antimycobacterial, antifungal and photosynthesis-inhibiting activities. The highest antituberculotic activity (72% inhibition) against Mycobacterium tuberculosis and the highest lipophilicity (log P = 6.85) were shown by the 3,5-bistrifluoromethylphenyl amide of 5-tert-butyl-6-chloropyrazine-2-carboxylic acid (2o). The 3-methylphenyl amides of 6-chloro- and 5-tert-butyl-6-chloro-pyrazine-2-carboxylic acid (2d and 2f) exhibited only a poor in vitro antifungal effect (MIC = 31.25-500 μmol·dm-3) against all strains tested, although the latter was the most active antialgal compound (IC50 = 0.063 mmol·dm-3). The most active inhibitor of oxygen evolution rate in spinach chloroplasts was the (3,5-bis-trifluoromethylphenyl)amide of 6-chloropyrazine-2-carboxylic acid (2m, IC50 = 0.026 mmol·dm-3).
TL;DR: In this paper, 3-(2-Furanyl)-4-amino-5-mercapto-1,2,4-triazole (1) was prepared from 2-furoic acid through a multi-step reaction sequence.
Abstract: 3-(2-Furanyl)-4-amino-5-mercapto-1,2,4-triazole (1) was prepared from 2-furoic acid through a multi-step reaction sequence. Compound 1 reacted with aromatic acids in the presence of phosphorus oxychloride to give 3-(2-furanyl)-6-aryl-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles (2). The structures of all the newly synthesized compounds have been confirmed by elemental analysis, IR, 1H-NMR, 13C-NMR and mass spectra. The bioassay indicated most of the title compounds possess significant growth promoting effects on mung bean radicles.
TL;DR: In this paper, two alternative and complementary one-pot procedures for the direct transformation of 2-amino alcohols to N-tosyl aziridines are presented, which use simple inorganic bases and produce only inorganic salts as byproducts.
Abstract: Two alternative and complementary one-pot procedures for the direct transformation of 2-amino alcohols to N-tosyl aziridines are presented. The unsubstituted parent compound and its less hindered homologues can be obtained in high yields by tosylation and in situ cyclisation effected by potassium hydroxide in water/dichloromethane. Higher substituted amino alcohols give better yields using potassium carbonate in acetonitrile. Both procedures use simple inorganic bases and produce only inorganic salts as byproducts.
TL;DR: In this paper, a combination of silica sulfuric acid and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under thermal conditions.
Abstract: Neat chlorosulfonic acid reacts with silica gel to give silica sulfuric acid in which sulfuric acid is immobilized on the surface of silica gel via covalent bonds. A combination of silica sulfuric acid and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under thermal conditions.
TL;DR: Two potentially heptadentate (N4O3) tripodal Schiff-base ligands: tris(3-(salicylideneimino)propyl)amine (H3L1) and tris (3-(4’-hydroxysalicylIDeniimino)-propyl), have been prepared and characterized by various spectroscopic methods (IR, FAB-MS, NMR).
Abstract: Two potentially heptadentate (N4O3) tripodal Schiff-base ligands: tris(3-(salicylideneimino)propyl)amine (H3L1) and tris(3-(4’-hydroxysalicylideneimino)-propyl)amine (H3L2) have been prepared and characterized by various spectroscopic methods (IR, FAB-MS, NMR). They are derived from the condensation reactions of tris(3-aminopropyl)amine (tpt), with 3 equivalents of either salicylaldehyde or the ringsubstituted salicylaldehyde, 4-hydroxysalicylaldehyde. The nickel(II) and copper(II) complexes of H3L1 were obtained from the its reactions Ni(II) and Cu(II) salts in absolute methanol. These complexes were studied by IR and FAB-Mass spectrometry.
TL;DR: In this article, the synthesis of 4-chloropyrrolo[2,3-d ]pyrimidines and triazolo[1,5-c ]pyrrolonopyrrole[3,2-e]pyridines were reported.
Abstract: : Syntheses of several novel 4-chloropyrrolo[2,3- d ]pyrimidines ( 1 ), 4-hydrazinopyrrolo[2,3- d ]pyrimidines ( 2 ) and 3-amino-4-iminopyrrolo[2,3- d ]pyrimidines ( 7 ) and their use in the synthesis of tetrazolo[1,5- c ]pyrrolo[3,2-e]pyrimidines ( 3 ) and triazolo[1,5- c ]pyrrolo[3,2- e ]pyrimidines ( 4 ) required for biological screening are reported. Keywords: Tetrazolopyrrolopyrimidines, triazolopyrrolopyrimidines, pyrrolo[2,3- d ]-pyrimidines, antibacterial activity Introduction It is well known that organofluorine compounds display a variety of interesting pharmacological and agrochemical properties [1-7]. Moreover, pyrimidines having halogen groups at positions 2 or 4 appear to be more labile, displaying powerful reactivity in nucleophilic substitution reactions with reagents such as piperidine, piperazine, morpholines, hydrazines, azides, etc. These replacements also permit the combination of two active moieties [8-9] forming potent bi- and triheterocycles [8-12]. Further, the resulting compounds were found to undergo reactions with carbon or nitrogen donor
TL;DR: In this article, 1,4-Dihydropyridines (DHPs) were used in the reduction of carbon-carbon double bonds under microwave irradiation without solvent.
Abstract: 1,4-Dihydropyridines (DHPs) have been used in the reduction of carbon-carbon double bonds under microwave irradiation without solvent. The efficiency of the reactions is dramatically dependent on the steric effects in the DHPs and on the electronic effects in the olefins.
TL;DR: In this paper, the photodimerization is also stereoselective, and the centrosymmetric stereoisomer 6 predominates over the non symmetric P-epimer 7.
Abstract: Diethyl 1,2-benzoxaphosphorine-3-carboxylates 5 undergo a regio- and stereoselective [2+2] photodimerization reaction in methanol solution under the action of sunlight, giving in all cases the corresponding anti head-to-tail dimers 6 and 7. Concerning the stereogenic P atom, the photodimerization is also stereoselective, and the centrosymmetric stereoisomer 6 predominates over the non symmetric P-epimer 7.
TL;DR: A correlation has been established between production of specific phenylphenalenones and resistance of various banana and plantain varieties towards certain pathogens.
Abstract: A correlation has been established between production of specific phenylphenalenones and resistance of various banana and plantain varieties towards certain pathogens. In addition a dihydrotrihydroxyphenylphenalene was isolated from the resistant 'Pelipita' plantain variety in relatively high concentrations and its structure and relative configuration were assigned on the basis of 1D and 2D NMR and NOE information. This compound is considered a key intermediate in the biosynthesis of phenylphenalenone phytoalexins.
TL;DR: In this paper, a novel class of anion receptors with with C-H···X- hydrogen bonding is introduced and demonstrated for Cl-, Br-, NO3- and HSO4- recognition.
Abstract: A novel class of anion receptors with with C-H···X- hydrogen bonding is introduced and demonstrated for Cl-, Br-, NO3- and HSO4- recognition. Cyclic voltammetry revealed that novel ferrocenylimidazolium salts, syntheses of which are briefly described, selectively complex and electrochemically recognise guest anions. Futhermore, proton NMR spectroscopy indicated the formation of 1:2 stoichiometric complexes with Cl-, Br and I- and 1:1 stoichiometric complexes with NO3- and HSO4-.
TL;DR: A review of 1,3-dipolar cycloaddition reactions of substituted benzyl azides with acetylenic compounds to form the corresponding 1,2-3-triazoles can be found in this paper.
Abstract: We review in this article some of our work which has been published over the last fifteen years in the area of 1,3-dipolar cycloaddition reactions of substituted benzyl azides with acetylenic compounds to form the corresponding 1,2-3-triazoles. Several triazole derivatives were transformed into triazolopyridazine and triazolo-1,3,4-oxadiazole derivatives upon their reactions with hydrazine. Keywords : Azides, 1,2,3-triazole, triazolopyridazine, triazolo-1,3,4-oxadiazole, 1,3-dipolar cycloaddition reactions. Introduction Azides are considered very important compounds due to both their industrial as well as biological applications [1]. Azide derivatives have been used in rubber vulcanization, polymer crosslinking, dyes, tire cored adhesives, foaming of plastics, pharmaceuticals, pesticides and herbicides [1]. Many azide compounds show mutagenic activities [2-4]. The chemistry of azides has thus attracted the attention of many chemists, since many of these compounds play an important role in organic chemistry [5-7]. One of the more useful synthetic applications of azides is the preparation of 1,2,3-triazoles via 1,3-dipolar cycloaddition reactions of azides with substituted acetylene compounds [8-13].
TL;DR: Manganese (III) meso-tetrakis (p-sulfonatophenyl)-β-octabromoporphyrin supported on Amberlite IRA-400 [Mn(Br8TPPS)-Ad-400] is a robust and efficient catalyst for epoxidation of alkenes and hydroxylation of alkanes with sodium periodate at room temperature.
Abstract: Manganese (III) meso-tetrakis(p-sulfonatophenyl)-β-octabromoporphyrin supported on Amberlite IRA-400 [Mn(Br8TPPS)-Ad-400] is a robust and efficient catalyst for epoxidation of alkenes and hydroxylation of alkanes with sodium periodate at room temperature.
TL;DR: A blue tetrapyrrole from Nembrotha kubaryana, the known nakafuran-8 and -9 from Hypselodoris infucata and spongiane-16-one from Chromodoris petechialis are isolated, supporting a link between diet and natural products in the nudibranchs.
Abstract: Nudibranchs are shell-less molluscs that are often brightly colored and seemingly defenseless against predation. However, these beautiful animals usually contain large amounts of diet-derived natural products that help defend them against predation. We have isolated a blue tetrapyrrole from Nembrotha kubaryana, the known nakafuran-8 and -9 from Hypselodoris infucata and spongiane-16-one from Chromodoris petechialis. These compounds have previously been found in other marine organisms, thus supporting a link between diet and natural products in the nudibranchs.
TL;DR: The [Cd(C5H5N)2(S2CO-n-C4H9)2]n was synthesized and characterized by IR, elemental analysis, 1H-NMR and X-ray diffraction analysis.
Abstract: The [Cd(C5H5N)2(S2CO-n-C4H9)2] adduct of pyridine with [Cd(S2CO-n-C4H9)2]n was synthesized and characterized by IR, elemental analysis,1H-NMR and X-ray diffraction analysis. The crystasl belong to the monoclinic system, space group P2(1)/c with Z=2. Cell dimensions are a=1.1094(12), b=0.6152(6), c=1.7985(19) nm, • =96.148(2)°, V=1.2204(2)nm3. The structure was refined to R=0.0246 and wR=0.0645 for 2624 reflections with I>2•(I). The complex has a centrosymmetric molecule structure.
TL;DR: In this paper, the reaction of N-(2-cyanophenyl)benzimidoyl chloride with reagents containing a thioamide moiety was studied.
Abstract: The reaction of N-(2-cyanophenyl)benzimidoyl chloride with reagents containing a thioamide moiety, ie thioacetamide, benzylthiourea, symmetrical dialkyl- and diarylthioureas gave different cyclic products: 3,1-benzothiazine, 1,3,5-benzotriazocine and quinazoline The reaction pathways of prepared compounds are discussed
TL;DR: In this article, the chemical composition of the essential oil of Psidium caudatum McVaugh was investigated and thirty-two compounds were identified by HRGC-MS.
Abstract: The chemical composition of the essential oil of Psidium caudatum McVaugh was investigated and thirty-two compounds were identified by HRGC-MS. The main constituents were terpinen-4-ol (47.72%), γ-terpinene (11.58%) and α-terpinene (6.70%).
TL;DR: In this paper, a new universal and diastereospecific method has been developed for the synthesis of 5,6-dihydropyridin-2(1H)-ones, 1,5,6,8,8ahexahydroisoquinolin-3(2H)-one and 4a, 5, 6, 7, 8, 8-8, 8a hexahydroid-quinolin 2(1.H) based on the intramolecular Wittig cyclization of the triphenyphosphonium salts
Abstract: A new, universal and diastereospecific method has been developed for the synthesis of 5,6-dihydropyridin-2(1H)-ones, 1,5,6,8,8a-hexahydroisoquinolin-3(2H)-ones and 4a,5,6,7,8,8ahexahydroquinolin-2(1H)-ones (4) based on the intramolecular Wittig cyclization of the triphenyphosphonium salts 2 derived from the N-(3-oxoalkyl)–chloroacetamides 1.
TL;DR: A number of pyridothienopyridine have been obtained via interaction of -amino-5-phenylamino-2,4-dicarbonitril3 e (1) with different reagents as discussed by the authors.
Abstract: A number of pyridothienopyridine 2 , 3 ), pyridothienopyrimidine 6 , 10 ), ( (pyridothienotriazine ( 13 ), pyrimidothienopyrimidine ( 15 , 16 , 17a,b ) and thienoimidazo-triazines ( 18 ) were obtained via interaction of -amino-5-phenylamino-2,4-dicarbonitril3 e (1) with different reagents. Keywords: pyridothienopyridines, pyridothienopyrimidines, thienotriazopyrimidines, pyridothienotriazines, pyrimidothienopyrimidines. Introduction Many thienopyridines have been evaluated pharmacologically and have been found to show activity against, for example, diabetes mellitus [1-3], as analgesics and antiinflammatories [4-6], sedatives [4], anticoagulants [6], antiartherosclerotics [7], and as gonadotropin releasing hormone antagonists [8]. Moreover the pyridothienopyrimidines showed analgesic and antiinflammatory activity [9]. In earlier communications, we have reported the syntheses and reactions of various thiophenes and fused thiophenes [10-12], which were prepared in one-pot reactions using phase transfer techniques (PTC). Also, several papers have reported the synthesis of polyfused heterocycles containing different nuclei [13-16], starting from fused thiophenes prepared in our laboratory.
TL;DR: The title compounds were synthesized from C-aryl-N-methylglycines by Naroylation followed by a cyclodehydration to form the corresponding 1,3-oxazolium-5-olates as discussed by the authors.
Abstract: The title compounds were synthesized from C-aryl-N-methylglycines by Naroylation followed by a cyclodehydration to form the corresponding 1,3-oxazolium-5-olates. These were not isolated but converted to the title compounds by an in situ 1,3-dipolar cycloaddition/cycloreversion sequence using carbon disulphide. We have studied the cyclodehydration step using acetic anhydride, trifluoroacetic anhydride and 1,3-dicyclohexylcarbodiimide (DCC) at temperatures not exceding 60oC. Trifluroacetic anhydride proved to be the best reagent, giving a better yield and more easily purified products, although yields were also acceptable with the other two reagents.