2,3-Seco-2,3-dioxo-lyngbyatoxin A from a Red Sea strain of the marine cyanobacterium Moorea producens

Chemical investigation of the organic extract of a Red Sea strain of the cyanobacterium Moorea producens has afforded 2,3-seco-2,3-dioxo-lyngbyatoxin A (1). Five known compounds including lyngbyatoxin A (2), majusculamides A and B (3 and 4), aplysiatoxin (5) and debromoaplysiatoxin (6) were also isolated. Their structures were elucidated by using HR-FAB-MS, 1D and 2D NMR analyses. The compounds were evaluated for antiproliferative activity against HeLa cancer cells. Lyngbyatoxin A (2) showed potent activity, with an IC₅₀ of 9.2 nM, while 5 and 6 displayed modest activity with IC₅₀ values of 13.3 and 3.03 μM, respectively. In contrast, compounds 1, 3 and 4 were inactive, with IC₅₀ values greater than 50 μM. The lack of cytotoxicity for 2,3-seco-2,3-dioxo-lyngbyatoxin A (1) demonstrates that the indole moiety in lyngbyatoxin (2) is essential for its cytotoxicity, and suggests that detoxification of 2 may be carried out by biological oxidation of the indole moiety to yield 1.     

A Benzylation Study of 2,3-Dichloronaphthazarin

Depending on different reaction time and temperature employed, benzylation of 2,3-dichloronaphthazarin (I) using silver oxide as the catalyst can form either exclusively 5,8-dibenzyloxy-6,7-dichloronaphthalene-1,4-dione (II), or exclusively 5-benzyloxy-2,3-dichloro-8-hydroxynaphthalene-1,4-dione (IV); or a mixture of II and 5,8-dibenzyloxy-2,3-dichloronaphthalene-1,4-dione (III). Structures of these compounds were identified by nmr analysis.     

Novel Syntheses of 2,3-Disubstituted Benzothiophenes

The sodium salts of o-sulfanylphenyl ketones 3a-g were treated with -benzotriazol-1-ylalkyl chlorides 4a,b to give intermediates 5a-k in good yields. Compounds 5a-k, on treatment successively with LDA and Ti (0), gave benzothiophenes 7a-k.     

Synthesis of 3-Substituted Xylopyrnosides from 2,3-Anhydropentosides

Abstract

The facile regio- and stereoselective epoxide ring-opening of anhydropentosides described herein provides an attractive pathway to 3-substituted analogs of pentosides. Benzyl 2,3-anhydro-β-D-ribopyranoside (2) and benzyl 2,3-anhydro-β-L-ribopyranoside (7) were obtained from benzyl β-D-arabinopyranoside (1) and benzyl β-L-arabinopyranoside (3) respectively. The anhydropentosides were converted to the corresponding new 3-amino derivatives (8, 9, 10, and 11), alkoxy derivatives (12, 13, and 14), and deoxy sugar (15) in high yield. Every conversion was a one-step reaction of the anhydroglycoside with the appropriate nucleophile. Side-products due to epoxide migration were not observed.     

Gould-Jacobs reaction of 6-amino-2,3-diphenylquinoxaline

Summary Catalytic hydrogenation of 2,3-diphenyl-6-nitroquinoxaline led to the corresponding amine1 which in turn afforded products3a-i on reaction with alkoxymethylene derivatives2a-i. Thermal cyclization of3b and3f yielded substituted pyrazinoquinolones5b and5f, respectively. Optimal conditions for the successful hydrolysis of ester5b were found. The structures of all products were deduced from their IR, UV,¹H, and¹³C NMR spectroscopic data.Dedicated to Prof.F. Sauter on the occasion of his 65th birthday     

Reactions of cyclic oxalyl compounds XXXIX. Reactions of 4-Ethoxycarbonyl-5-phenyl-2,3-dihydrofuran-2,3-dione with heterocumulenes andSchiff bases

Summary Furan-2,3-dione1 reacts with arylisocyanates to the corresponding pyrrol-2,3-diones2, whereas conversion with diisopropylcarbodiimide affords the oxazepin-6,7-dione derivative3 in 68% yield. 1,3-Oxazines5,6, and7 were obtained by thermolysis of1 in boiling xylene in presence of arylisocyanates, diphenylketen-p-tolylimine, andSchiff bases, most likely by trapping the -oxoketene intermediate4. Preparative flash vakuum pyrolysis (FVP) of1 and2b gave8 and9, respectively.

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Reaktionen cyclischer Oxalylverbindungen, 39. Mitt. Umsetzungen von 4-Ethoxycarbonyl-5-phenylfuran-2,3-dion mit Heterocumulenen undSchiffschen Basen

Zusammenfassung Das Furan-2,3-dion1 reagiert mit Arylisocyanaten zu den entsprechenden Pyrrol-2,3-dionen, wohingegen mit Diisopropylcarbodiimid das 1,3-Oxazepinderivat3 in 68%iger Ausbeute gebildet wird. Die 1,3-Oxanzine5,6 und7 werden durch Thermolyse von1 in siedendem Xylol in Gegenwart von Arylisocyanaten, Diphenylketen-p-tolylimin undSchiffschen Basen erhalten, offensichtlich durch Abfangen des intermediär gebildeten -Oxoketens4. Präparative Flash-Vakuum-Pyrolyse (FVP) von1 bzw.2b ergaben8 bzw.9.

     

Synthese von 4H-Pyrano[2,3-d]pyrimidinen

Summary Good yields of substituted 5-(5R-2-furyl)-4H-pyrano[2,3-d]pyrimidines4 were obtained in the reaction of 2-ethoxymethyleneamino-3-cyano-4H-pyranes2 with ammonia. Compounds2 were prepared by the condensation of the starting 2-amino-5-acetyl-3-cyano-6-methyl-4H-pyranes1 with ethyl orthoformate. Spectral properties of the bicyclic system4 in relation to compounds3 are discussed.

     

Photochemical Reactions of Benzo[b]Thiophene-2,3-Diones with 2,3-Dimethylbut-2-Ene

Abstract

Photochemical reactions of benzo[b]thiophene-2,3-diones with 2,3-dimethylbut-2-ene gave dioxene derivatives in excellent yields.     

Synthesis and Reactions of Some New Heterocyclic Compounds Related to Pyrrolylthieno[2,3-d]pyrimidines and Thieno[2,3-d][4,5-d]dipyrimidines

Abstract

Condensation of ethyl-5-amino-2,4-diphenylthieno[2,3-d]pyrimidine-6-carboxylate (3a) with 2,5-dimethoxy tetrahydrofurane in acetic acid gives the corresponding 5-pyrrolyl derivative4, which in turn could be easily reacted with hydrazine hydrate in ethanol yielding the carbohydrazide derivative5. Reaction of5 with aromatic aldehydes, acetylacetone, carbon disulfide or phenylisothiocyanate gave pyrrolyl derivatives6,7,8,9 respectively. On the other hand, condensation of 5-(1-pyrrolyl)-6-acetyl-2,4-diphenylthieno[2,3-d]pyrimidine11 with benzaldehyde afforded the corresponding chalcone12, which on treatment with hydrazine hydrate, phenyl hydrazine, or thiourea gave the pyrazolinyl derivatives13,14 and pyrimidinyl derivative15, respectively. Furthermore some new pyrimidothienopyrimidne16,17a–d,19,20a–c were obtained using 5-amino-carboxamide3c as starting material.     

HYDROCHLORINATION OF 2,3-ACETYLENIC ACIDS WITH THIONYL CHLORIDE IN DIMETHYLFORMAMIDE

ABSTRACT

The reaction of 2,3-acetylenic acids (1a–d) with thionyl chloride in DMF under mild conditions gave E,Z-3-chloro-2-alkenoic acids (2a–d) or esters (3a–d) depending on treating the reaction mixture with either water or alcohols.     

Facile Syntheses of Some Thieno[2,3-d] Pyrimidine Derivatives

In one-pot synthesis 2-arylidene-5,6,7,8-tetrahydrothiazolo[3,2-a] cyclopenteno-thieno[2,3-d] pyrimidine-3,5-diones (3) were prepared via the reaction of a ternary mixture of 2-thioxo-1,3,4,5,6,7-hexahydr cyclopentinothieno [2,3-d]-4-one (2), chloroacetic acid and a proper aldehyde. Compound 2 reacted with 3-chloropent-2, 4-dione in ethanolic potassium hydroxide yielding the S-acetyl acetone derivative 5f . The latter compound reacted with hydrazine hydrate and phenyl hydrazine yielded the 2-pyrazolthio derivative 10a, b. Compound 5f also underwent cyclization on heating with acetic acid—pyridine solution to give 11. The 2-methylthio derivative 5a, when treated with hydrogen peroxide gave the corresponding oxidized product 9.     

Synthesis and reactions of 2,3-dimethylfuro[3,2-c]pyridines

Summary A number of substituted 2,3-dimethylfuro[3,2-c]pyridines was synthesized. 3-(4,5-Dimethyl-2-furyl)propenoic acid (1) was converted to the acid azide2, which in turn was cyclized to give 2,3-dimethyl-5H-furo[3,2-c]pyridine-4-one (3) by heating at 240°C in Dowtherm. The pyridone3 was chlorinated with phosphorus oxychloride to give4, which was reduced with zinc and acetic acid to 2,3-dimethylfuro[3,2-c]pyridine (5). Treatment of4 with several secondary heterocyclic amines led to compounds6a–6c. Reaction of pyridone3 with phosphorus pentasulfide rendered the thione7, which was methylated to8a. The 4-methoxy derivative8b was obtained from4 with sodium methoxide. 2,3,5-Trimethylfuro[3,2-c]pyridine-4-one (9) was obtained by reaction of3 with methyl iodide.Dedicated to Professor Dr.Fritz Sauter on the occasion of his 65th birthday     

2,3-Diphenylphosphirenepentacarbonyltungsten Complex: Synthesis and Reactivity

Abstract

2-3-Diphenylphosphirenepentacarbonyltungsten complex 1 is prepared using the following scheme :     

Enantiomerentrennung und chiroptische Eigenschaften eines 2,3-Dihydrobilatriens-abc

The enantiomers of the 2,3-dihydrobilatriene-abc1 have been separated by recycling chromatography on triacetylcellulose. Comparison of their chiroptical properties with those of amino acid substituted analogues, like3, reveals the chirality of center 3 to be of minor influence on the values. Stabilization of a definite helical conformation of these pigments seems to depend on this influence together with an appropriate dipole-dipole interaction.

     

Nucleophilic Opening of N-Carboalkoxy-2,3-anhydro-1-deoxymannojirimycin. A Useful Method for the Syntheses of 2-, 3- and 2,3-Disubstituted 1-Deoxynojirimycin Analogs

Abstract

A useful methodology for the synthesis of a number of 2-, 3- and 2,3-disubstituted deoxynojirimycin analogs is reported. It has been found that the epoxides in stereoselectively synthesized N-carboalkoxy-2,3-anhydro-1-deoxymannojirimycins (4 and 5) react with N-, S- and F- nucleophiles to give a mixture of gluco and altro products. The 3-azido altro compound (12b) yields the desired gluco derivative (40) by oxidation, in situ epimerization at C-3, followed by stereoselective reduction of the carbonyl group. The azido intermediate (12a) affords the 2,3-diazido gluco compound (51) by double inversion at C-3. Attempts have been made to understand the factors contributing to the opening of epoxides (4, 5 and 9) by different nucleophiles.     

Synthesis and Crystal Structures of Group 10 Metal Bis(dithiolate) Complexes Constructed by 2,3-Naphtho-15-Crown-5 or 2,3-Naphtho-18-Crown-6

Five novel 2,3-naphtho crown ether group 10 metal bis(dithiolate) complexes, [Na(N15C5)₂]₂[Pd(mnt)₂] (1), [Na(N15C5)]₂[Pd(i-mnt)₂] (2) and [K(N18C6)]₂[M(i-mnt)₂] (3 5) (where mnt = 1,2-dicyanoethylene-1,2-dithiolate, i-mnt = 1,1-dicyanoethylene-2,2-dithiolate and M = Ni, Pd, Pt for complexes 3–5, respectively), have been synthesized and characterized by elemental analysis, FT-IR, UV–Visible spectra and single crystal X-ray diffraction. X-ray diffraction analyses reveal that complexes 1 and 2 have different structural features while complexes 3–5 are structurally isomorphous. Complex 1 consists of two [Na(N15C5)₂]⁺ sandwich complex cations and one [Pd(mnt)₂]²⁻ anion, affording a zero-dimensional structure. For 2, the [Na(N15C5)]⁺ mono-capped complex cations act as the bridges linking the [Pd(i-mnt)₂]²⁻ anions into a 1D infinite chain through Na–N interactions and SȮFC and SȮFπ interactions are observed in the resulting chain. Complexes 3–5 all consist of two [K(N18C6)]⁺ complex cations and one [M(i-mnt)₂]²⁻ (M = Ni, Pd or Pt) anion and the complex molecules are linked into␣1D␣chains by the bridging K–O(ether) interactions between the adjacent [K(N18C6)]⁺ units. What’s novel is that the resulting chains are assembled into novel 2D networks through interchain π–π stacking interactions between the neighboring naphthylene moieties of N18C6. The stack model of naphthylene group in complexes 3–5 is discussed.     

Convenient Syntheses of Methyl 2-Bromo- and 2-Iodo-2,3-butadienoates

Syntheses of methyl 2-bromo- and 2-iodo-2,3-butadienoates 3 and 6 from readily available starting materials are described. 3 and 6 will be valuable building blocks for the synthesis of 2-aryl and 2-alkenyl substituted alka-2,3-dienoates via Palladium-catalyzed cross-coupling reactions.     

Synthesis of Indolo[2,3-a]quinolizidine-3-One

The title compound 1 has been synthesised through the intermediacy of the salt 5 obtained by acid hydrolysis of the obtically active β-carboline derivative 10,11-cyclohexylidene-12β-hydroxy-13β-(l-tetrahydro-β-carbolinyl)tetrahydrofuran (4).     

Synthesis of 2H-pyrano[2,3-d]pyrimidine derivatives

Two series of 2H-pyrano[2,3-d]pyrimidine-2,5(6H)-dione derivatives have been prepared. Thus, the reaction of 6-hydroxy-pyrimidin-4(3H)-ones (1 a–c) with bis-2,4,6-trichlorphenyl malonates (2 a–d) or diethyl malonates (3 a–d) afforded good yields of 4-hydroxy-2H-pyrano[2,3-d]pyrimidine-2,5(6H)-diones (4 a-l). Application of our modifiedPechmann reaction^9–11 using -aminocrotonate (5) or -keto esters (6, 7) in the presence of ammonium acetate yielded the 2H-pyrano[2,3-d]pyrimidinediones8 a–h.Dedicated to Prof. Dr.Karl Schlögl, University of Vienna, on the occasion of his 60th birthday.     

Synthesen von 4-Amino-thieno[2,3—b]pyridinen

The Cyclization of 2-(1,1-dicyanovinylamino)-thiophenes2 by treatment with AlCl₃ yield 4-amino-5-cyano-thieno[2,3-b]pyridines3. 2-(1-acylvinyl-amino)-3-cyano-thiophenes7, obtainable from 2-amino-3-cyano-thiophenes and -diketones, react in the presence of AlCl₃ to form 4-acylamino-thieno[2,3-b] pyridines8. This reaction is connected with the transfer of the acyl group from C- to the N-atom. 4-Amino-5-cyano-thieno[2,3-b]pyridones-(6)11 are synthesized from 2-amino-3-cyano-thiophenes and ethyl cyano acetate in the presence of sodium ethoxide.