Regio‐ and stereoselective synthesis of spiro[1‐benzothiepine‐4(5h), 3′(3h)‐pyrazol]‐5‐ones

Reaction of (4E)‐4‐arylmethylene‐3,4‐dihydro‐1‐benzothiepin‐5(2H)‐ones 3a‐e with nitrilimines (generated in situ via triethylamine dehydrohalogenation of the corresponding hydrazonoyl chlorides 4a, b ) in refluxing benzene, afforded 2′,4′,5′‐triaryl‐2,2′,3,4′‐tetrahydro‐spiro[1‐benzothiepine‐4(5H),3′(3H)‐pyrazol]‐5‐ones 5a‐i and not the isomeric forms spiro[1‐benzothiepine‐4(5H),4′(4H)‐pyrazol]‐5‐ones 6 in high regioselective manner. Single crystal X‐ray diffraction studies of 5a, f, g indicated that the isolated products are 3′R, 4′ S.     

Two stereoisomeric pentacyclic oxin­dole alkaloids from Uncaria tomentosa: uncarine C and uncarine E

The chloro­form solvate of uncarine C (pteropodine), (1′S,3R,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octa­hydro‐1′‐methyl‐2‐oxospiro­[3H‐indole‐3,6′(4′aH)‐[1H]­pyrano­[3,4‐f]indolizine]‐4′‐carboxyl­ic acid methyl ester, C₂₁H₂₄N₂O₄·CHCl₃, has an absolute configuration with the spiro C atom in the R configuration. Its epimer at the spiro C atom, uncarine E (isopteropodine), (1′S,3S,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octahydro‐1′‐methyl‐2‐oxospiro[3H‐indole‐3,6′(4′aH)‐[1H]pyrano[3,4‐f]indolizine]‐4′‐carboxylic acid methyl ester, C₂₁H₂₄N₂O₄, has Z′ = 3, with no solvent. Both form intermolecular hydrogen bonds involving only the ox­indole, with N?O distances in the range 2.759 (4)–2.894 (5) Å.     

An Efficient Synthesis of 1′,7′,8′,9′‐Tetrahydrospiro[indoline‐3,4′‐pyrazolo[3,4‐b]quinoline]‐2,5′(6′H)‐dione Derivatives in Aqueous Medium

An efficient and green reactions of isatins, 3‐amine‐1H‐pyrazole (5‐methyl‐1H‐pyrazol‐3‐amine) and 1,3‐diketone in aqueous medium for the synthesis of novel 1′,7′,8′,9′‐tetrahydrospiro[indoline‐3,4′‐pyrazolo[3,4‐b]quinoline]‐2,5′(6′H)‐dione derivatives were reported in this research. The advantages of this reaction are simple operation, mild‐reaction conditions, wide scope substrate, high yields, and friendly environment. The products were confirmed by IR, ¹H NMR, ¹³C NMR, and HRMS.     

Syntheses of Some 3—[1′（1′H）—Substituent—pyrazol—5′—yl] benzo [5,6] coumarins

3-[1′(1′H)-Substituent-pyrazol-5′-yl]benzo[5,6]coumarins and 3-(1′,2′-oxazol-5′-yl)benzo[5,6]coumarin were prepared via condensation of 3-(2′-formyl-1′-chlorovinyl)benzo[5,6] coumarin with hydrazine derivatives or hydroxylamine.Reaction of 3-[1′(1′H)-pyrazol-5′-yl]benzo[5,6]coumarin with alkyl halides,olefinic compunds or acid chlorides are described.     

Synthesis of novel pyrido[3′,2′:5,6]thiopyrano[3,2‐b]indol‐5(6H)‐ones and 6H‐pyrido[3′,2′:5,6]thiopyrano[4,3‐b]quinolines,two new heterocyclic ring systems

The synthesis of new pyrido[3′,2′:5,6]thiopyrano[3,2‐b]indol‐5(6H)‐ones was accomplished by the Fischer‐indole cyclization of some 2,3‐dihydro‐3‐phenylhydrazonothiopyrano[2,3‐b]pyridin‐4(4H)‐ones, obtained from the 2,3‐dihydro‐3‐hydroxymethylenethiopyrano[2,3‐b]pyridin‐4(4H)‐one, by the Japp‐Klingemann reaction. 6H‐Pyrido[3′,2′:5,6]thiopyrano[4,3‐b]quinolines were obtained by reaction of 2,3‐dihydrothiopyrano‐[2,3‐b]pyridin‐4(4H)‐ones with o‐aminobenzaldehyde or 5‐substituted isatins. The preparation of some derivatives, functionalized with an alkylamino‐substituted side chain, is also described.     

A Versatile Synthesis,PM3‐Semiempirical,Antibacterial, and Antitumor Evaluation of Some Bioactive Pyrazoles

This research work describes the synthesis and biological properties of some novel isolated or fused heterocyclic ring systems with pyrazole, for example; enaminones containing pyrazolone ring photochromic functional unit, 4‐[(4‐chlorophenylamino)methylene]‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐one (3) and some analogous derivatives 4, 9, and 10, also as pyrazolo[3,4‐b]pyridine, pyrazolo[3,4‐b]quinoline, pyrazolo[3′,4′:4,5]thieno[2,3‐c]pyrazoline and pyrazolo[3,4‐c]pyrazole were synthesized and characterized. Newly synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, mass spectral data and quantum mechanical calculations. Selected products were tested for their antibacterial and antitumor agents.     

Conformationally restricted tricyclic analogues of lipophilic pyrido[2,3‐d]pyrimidine antifolates

The effect of conformational restriction of the C9‐N10 bridge on inhibitory potency and selectivity of trimetrexate against dihydrofolate reductase, was studied. Specifically three nonclassical tricyclic 1,3‐diamino‐8‐(3′,4′,5′‐trimethoxybenzyl)‐7,9‐dihydro‐pyrrolo[3,4‐c]pyrido[2,3‐d]pyrimidin‐6(5H,8H)‐one ( 4 ), 1,3‐diamino‐8‐(3′,4′,5′‐trimethoxybenzyl)‐9‐hydro‐pyrrolo[3,4‐c]pyrido[2,3‐d]pyrimidin‐6‐(8H)‐one ( 5 ) and 1,3‐diamino‐(8H)‐(3′,4′,5′‐trimethoxybenzyl)‐7,9‐dihydro‐pyrrolo[3,4‐c]pyrido[2,3‐d]pyrimidine ( 7 ) antifolates were synthesized. The tricyclic analogues 4 and 5 were obtained via the regiospecific cyclo‐condensation of the β‐keto ester 17 with 2,4,6‐triaminopyrimidine. The analogue 7 was obtained via reduction of the lactam 4 with borane in tetrahydrofuran. Compounds 4, 5 and 7 were evaluated as inhibitors of dihydrofolate reductase from Pneumocystis carinii, Toxoplasma gondii and rat liver. All three compounds were more selective than trimetrexate against Pneumocystis carinii dihydrofolate reductase and significantly more selective than trimetrexate against Toxoplasma gondii dihydrofolate reductase compared with rat liver dihydrofolate reductase.     

Isatins 3-C annulation vs ring-opening: Two different pathways for synthesis of spiro compounds via multicomponent reactions

An efficient synthesis of spiro compounds via two different pathways from the reactions of isatins, 3-phenylisoxazol-5(4H)-one (3-ethylisoxazol-5(4H)-one), and pyrazol-5-amine (6-aminopyrimidine-2,4(1H,3H)-dione) were reported. The catalyst Amberlyst-15 could be easy recycled and reused for many time without any appreciable loss in catalytic activity. The new type spiro compounds were gained through the ring-opening of isatins process. The structures of spiro[indoline-3,4′-isoxazolo[5,4-b]pyrazolo[4,3-e]pyridin]-2-one, spiro[isoxazolo[5,4-b]quino line-4,5′-pyrrolo[2,3-d]pyrimidine]-2′,4′,6′(1′H,3′H,7′H)-trione, and spiro[indoline-3,4′-pyrazolo[3,4-b]pyridine]-2,6′(5′H)-dione were successfully confirmed by ¹H NMR, ¹³C NMR, HRMS, and X-ray crystal diffraction analysis.     

Investigation of the Reactions of Indole‐2,3‐diones with Biuret: A Novel Approach for the Synthesis of Spiro[indole‐triazines]

Reactions of indole‐2,3‐diones with biuret afforded 1,3‐dihydro‐3‐ureidoformimido‐2H‐indol‐2‐ones and spiro[3H‐indole‐3,2′(1′H )‐(1,3,5)triazine]‐2,4′,6′(1H ,3′H ,5′H )‐triones indicated these to be solvent dependent. The chemical structures of the products were elucidated by their comprehensive spectroscopic (IR, ¹H‐NMR, ¹³C‐NMR, ¹⁹F‐NMR, and Mass) as well as analytical analysis.     

Synthesis of novel 1,4‐dihydropyrido[3′,2′:5,6]thiopyrano[4,3‐c]‐pyrazoles and 5H‐pyrido[3′,2′:5,6]thiopyrano[4,3‐d]pyrimidines as potential antiproliferative agents

The synthesis of new planar derivatives characterized by the presence of a pyridothiopyranopyrazole or pyridothiopyranopyrimidine nucleus, carrying a substituted aryl group, is reported. The novel 1,4‐dihydropyrido[3′,2′:5,6]thiopyrano[4,3‐c]pyrazole derivatives were obtained by condensation of 2,3‐dihydro‐3‐hydroxymethylenethiopyrano[2,3‐b]pyridin‐4(4H)‐ones with appropriate hydrazines. The preparation of 2‐substituted pyrido[3′,2′:5,6]thiopyrano[4,3‐d]pyrimidines was accomplished from the intermediate 2,3‐dihy‐dro‐3‐dimethylaminomethylenethiopyrano[2,3‐b]pyridin‐4(4H)‐ones by reaction with the appropriate binucleophile amidines. The antiproliferative activity of some new products was tested by an in vitro assay on human tumour cell lines (HL‐60 and HeLa), but none of them showed any significant effects in the tests performed. Accordingly, linear flow dichroism measurements indicated their inability to form a molecular complex with DNA.     

One pot synthesis of 6,12‐dihydro‐1,3,7,9‐tetramethyl‐5H, 11H‐dipyrido[1,2‐a:1′,2′‐d]pyrazine‐2,8‐dione by hilbert‐johnson reaction of 2‐chloromethyl‐3,5‐dimethyl‐4‐methoxypyridine

By heating 2‐chloromethyl‐3,‐5‐dimethyl‐4‐methoxypyridine (1) either neat or in solution methoxy group cleavage was achieved, followed by dimerisation to poorly soluble 6,12‐dihydro‐1,3,7,9‐tetramethyl‐5H,11H‐dipyrido[1,2‐a:1′,2′‐d]pyrazine‐2,8‐dione (3) in almost quantitative yield with methyl chloride evolution. To our knowledge this is the first example of such Hilbert‐Johnson preparation of dipyridopyrazine‐diones. Recrystallization of 3 from the hydrochloric acid yielded 6,12‐dihydro‐2,8‐dihydroxy‐1,3,7,9‐tetramethyl‐dipyrido[1,2‐a:1′,2′‐d]pyrazinediylium dichloride (4) , neutralization of which gave back the pyrazine‐2,8‐dione 3. The molecular structures of both compounds 3 and 4 have been unambiguously confirmed by single crystal X‐ray structure analysis.     

Reduced 3,4′‐bipyrazoles from a simple pyrazole precursor: synthetic sequence,molecular structures and supramolecular assembly

The reaction of 5‐chloro‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde and N‐benzylmethylamine under microwave irradiation gives 5‐[benzyl(methyl)amino]‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde, C₁₉H₁₉N₃O, (I). Subsequent reactions under basic conditions, between (I) and a range of acetophenones, yield the corresponding chalcones. These undergo cyclocondensation reactions with hydrazine to produce reduced bipyrazoles which can be N‐formylated with formic acid or N‐acetylated with acetic anhydride. The structures of (I) and of representative examples from this reaction sequence are reported, namely the chalcone (E )‐3‐{5‐[benzyl(methyl)amino]‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐4‐yl}‐1‐(4‐bromophenyl)prop‐2‐en‐1‐one, C₂₇H₂₄BrN₃O, (II), the N‐formyl derivative (3RS )‐5′‐[benzyl(methyl)amino]‐3′‐methyl‐1′,5‐diphenyl‐3,4‐dihydro‐1′H ,2H‐[3,4′‐bipyrazole]‐2‐carbaldehyde, C₂₈H₂₇N₅O, (III), and the N‐acetyl derivative (3RS )‐2‐acetyl‐5′‐[benzyl(methyl)amino]‐5‐(4‐methoxyphenyl)‐3′‐methyl‐1′‐phenyl‐3,4‐dihydro‐1′H ,2H‐[3,4′‐bipyrazole], which crystallizes as the ethanol 0.945‐solvate, C₃₀H₃₁N₅O₂·0.945C₂H₆O, (IV). There is significant delocalization of charge from the benzyl(methyl)amino substituent onto the carbonyl group in (I), but not in (II). In each of (III) and (IV), the reduced pyrazole ring is modestly puckered into an envelope conformation. The molecules of (I) are linked by a combination of C—H…N and C—H…π(arene) hydrogen bonds to form a simple chain of rings; those of (III) are linked by a combination of C—H…O and C—H…N hydrogen bonds to form sheets of R ²₂(8) and R ⁶₆(42) rings, and those of (IV) are linked by a combination of O—H…N and C—H…O hydrogen bonds to form a ribbon of edge‐fused R ²₄(16) and R ⁴₄(24) rings.     

Indoloquinazoline Alkaloids from Araliopsis tabouensis

Three new indoloquinazolidine‐type alkaloids, 8,13‐dihydro‐2‐methoxyindolo[2′,3′: 3,4]pyrido[2,1‐b]quinazolin‐5(7H)‐one ( 1 ), 8,13‐dihydro‐2‐methoxy‐13‐methylindolo[2′,3′: 3,4]pyrido[2,1‐b]quinazolin‐5(7H)‐one ( 2 ), and 5,8,13,14‐tetrahydro‐2‐methoxy‐14‐methyl‐5‐oxo‐7H‐indolo[2′,3′: 3,4]pyrido[2,1‐b]quinazolim‐6‐iun chloride ( 3 ) were isolated from Araliopsis tabouensis, together with three known compounds. The structures of the new compounds were determined primarily from 1D‐ and 2D‐NMR analysis. The antimalarial activities of compounds 1 – 5 were evaluated against Plasmodium falciparum D6 and W2 clones. The IC₅₀ values in antimalarial bioassay for compounds 2 – 5 varied from 1.8 to 4.7 μg/ml.     

Green Synthesis of Spiro[indoline‐3,4′‐pyrazolo[3,4‐b][1,6]naphthyridine]‐2,5′(1′H)‐diones Catalyzed by TsOH in Ionic Liquids

A three‐component reaction of isatin, 3‐methyl‐1‐phenyl‐1H‐pyrazol‐5‐amine, and piperidine‐2,4‐dione was treated in ionic liquids catalyzed by TsOH and provided an efficient and green method for the synthesis of spiro[indoline‐3,4′‐pyrazolo[3, 4‐b][1,6]naphthyridine]‐2,5′(1′H)‐dione derivatives in high yields.     

Three‐component synthesis of spiro[indoline‐3,5′‐pyrimido[4,5‐b]quinoline]‐triones in water

A one‐pot, three‐component method for the efficient and simple synthesis of novel 2′‐amino‐8′,9′‐dihydro‐3′H‐spiro[indoline‐3,5′‐pyrimido[4,5‐b]quinoline]‐2,4′,6′(7′H,10′H)‐trione derivatives in aqueous media is reported. J. Heterocyclic Chem., (2011).     

Synthesis and Anticancer Activity of Some New Fused Pyrazoles and Their Glycoside Derivatives

4‐(4‐Chlorobenzylidene)‐2,5‐diphenyl‐2,3‐dihydro‐3H‐pyrazol‐3‐one 3a and 4‐(3,4‐dimethoxybenzylidene)‐5‐phenyl‐2,3‐dihydro‐3H‐pyrazol‐3‐one 3b were prepared and were reacted with phenylhydrazine, thiosemicarbazide, hydroxylamine hydrochloride, ethyl acetoacetate, diethylmalonate, malononitrile, ethyl cyanoacetate, and thiourea yielding fused pyrazole derivatives. Some of the new compounds were reacted with cyclic and acyclic sugars to produce new S‐, O‐, and N‐glycoside derivatives. The antitumor activity against the human breast cancer cells (MCF‐7) was assessed. Four of the new compounds showed IC₅₀ values less than those of the positive control, indicating that these four compounds are better anticancer agents than doxorubicin.     

Non‐iterative Asymmetric Synthesis of C15 Polyketide Spiroketals

The 2,2′‐methylenebis[furan] ( 1 ) was converted to 1‐{(4R,6S))‐6‐[(2R)‐2,4‐dihydroxybutyl]‐2,2‐dimethyl‐1,3‐dioxan‐4‐yl}‐3‐[(2R,4R)‐tetrahydro‐4,6‐dihydroxy‐2H‐pyran‐2‐yl)propan‐2‐one ((+)‐ 18 ) and its (4S)‐epimer (?)‐ 19 with high stereo‐ and enantioselectivity (Schemes 1–3). Under acidic methanolysis, (+)‐ 18 yielded a single spiroketal, (3R)‐4‐{(1R,3S,4′R,5R,6′S,7R)‐3′,4′,5′,6′‐tetrahydro‐4′‐hydroxy‐7‐methoxyspiro[2,6‐dioxabicyclo[3.3.1]nonane‐3,2′‐[2H]pyran]‐6′‐yl}butane‐1,3‐diol ((?)‐ 20 ), in which both O‐atoms at the spiro center reside in equatorial positions, this being due to the tricyclic nature of (?)‐ 20 (methyl pyranoside formation). Compound (?)‐ 19 was converted similarly into the (4′S)‐epimeric tricyclic spiroketal (?)‐ 21 that also adopts a similar (3S)‐configuration and conformation. Spiroketals (?)‐ 20 , (?)‐ 21 and analog (?)‐ 23 , i.e., (1R,3S,4′R,5R,6′R)‐3′,4′,5′,6′‐tetrahydro‐6′‐[(2S)‐2‐hydroxybut‐3‐enyl]‐7‐methoxyspiro[2,6‐dioxabicyclo[3.3.1]nonane‐3,2′‐[2H]pyran]‐4′‐ol, derived from (?)‐ 20 , were assayed for their cytotoxicity toward murine P388 lymphocytic leukemia and six human cancer cell lines. Only racemic (±)‐ 21 showed evidence of cancer‐cell‐growth inhibition (P388, ED₅₀: 6.9 μg/ml).     

Synthesis of Pyrano‐ and Pyrido‐Anellated Pyranosides as Precursors for Nucleoside Analogues

The push‐pull activated methyl (3Z)‐4,6‐O‐benzylidene‐3‐[(methylthio)methylene]‐3‐deoxy‐α‐D‐erythro‐hexopyranosid‐2‐ulose (1) reacted with dialkyl malonate in the presence of potassium carbonate to give the alkyl (2R,4aR,6S,10bS)‐4a,6,8,10b‐tetrahydro‐6‐methoxy‐8‐oxo‐2‐phenyl‐4H‐pyrano[3′,2′:4,5]pyrano[3,2‐d][1,3]dioxine‐9‐carboxylates 2 and 3. Treatment of 1 with 3‐oxo‐N‐phenyl‐butyramide, N‐(4‐methoxy‐phenyl)‐3‐oxo‐butyramide, and 3‐oxo‐N‐o‐tolyl‐butyramide, respectively, in the presence of potassium carbonate and 18‐crown‐6 yielded the (2R,4aR,6S,10bS)‐9‐acetyl‐7‐aryl‐4,4a,7,10b‐tetrahydro‐6‐methoxy‐2‐phenyl[1,3]dioxino‐[4′,5′:5,6]pyrano[3,4‐b]pyridin‐8(6H)‐ones 4–6. (2R,4aR,6S,10bS)‐4,4a,8,10b‐Tetrahydro‐6‐methoxy‐8‐oxo‐2‐phenyl‐4H‐pyrano[3′,2′:4,5]pyrano[3,2‐d][1,3]dioxine‐9‐carboxamide (7) was prepared by anellation reactions of 1 either with malononitrile or with cyanoacetamide.     

Cytotoxic Constituents of Piper sintenense

A new pyridone alkaloid, 5,6‐dihydro‐5‐hydroxy‐1H‐pyridin‐2‐one ( 1 ), and a new ester, sintenin (=3‐(3,4‐dimethoxyphenyl)propyl 3‐(3,4‐dimethoxyphenyl)propanoate 2 ), together with three known compounds, 5,6‐dihydro‐1H‐pyridin‐2‐one ( 3 ), d‐sesamin (=5,5′‐(3a,4,6,6a‐tetrahydro‐1H,3H‐furo[3,4‐c]furan‐1,4‐diyl)bis[1,3‐benzodioxole]; 4 ), and (E)‐phytol (=3,7,11,15‐tetramethylhexadec‐2‐en‐1‐ol; 5 ) have been isolated from the whole plant of Piper sintenense. The structures of the two new compounds were determined through spectral analyses. Among twenty isolates obtained so far, four compounds exhibited effective cytotoxicities against P‐388, HT‐29, or A549 cell lines in vitro.     

Two New Citrinin Dimers from a Volcano Ash‐Derived Fungus,Penicillium citrinum HGY1‐5

Two new citrinin dimers, penidicitrinin A ((2R,3S,5aS,9R,10S,12aR,12bR)‐2,3,5a,6,9,10,12a,12b‐octahydro‐7,12a‐dihydroxy‐12b‐methoxy‐2,3,4,9,10,11‐hexamethyl‐5H‐difuro[2,3‐b : 2′,3′‐h]xanthen‐5‐one; 1 ) and penidicitrinin B ((1S,3R,4S)‐1‐{2,6‐dihydroxy‐4‐[(1S,2R)‐2‐hydroxy‐1‐methylpropyl]‐3‐methylphenyl}‐3,4‐dihydro‐3,4,5‐trimethyl‐1H‐2‐benzopyran‐6,8‐diol; 2 ), together with three known citrinin monomers were isolated from a volcano ash‐derived fungus, Penicillium citrinum HGY1‐5. Their structures were established by spectroscopic methods, and they showed no cytotoxicity against two tumor cell lines.