Streptonigrin and related compounds IV. Precursors for the a-ring

The synthesis of streptonigrin or its tricyclic (ABC) analogues by the Friedlander condensation requires a 2-nitrobenzaldehyde with all the necessary functionalities. A number of alternative syntheses are examined. It is shown that oxidation of 8-amino-5,6-dimethoxy-2,2-pyridylquinoline leads to 8-amino-2,2-pyridylqunoline-5,6-dione instead of 6-methoxy-2,2-pyridylquinoline-5,8-dione. The synthesis of two useful precursors: 4-bromo-3-hydroxy-5,6-dimethoxy-2-nitrobenzaldehyde and 4-bromo-3-hydroxy-5-methoxy-2-nitrobenzaldehyde is described.     

Synthesis of 4-chloro-7-ethoxy-2(3H)-benzoxazolone-6-carboxylic acid

As a part of metabolic studies of mosapride ( 1 ), a potential gastroprokinetic agent, the synthesis of 4-chloro-7-ethoxy-2(3H)-benzoxazolone-6-carboxylic acid ( 7 ) as a derivative of 4-amino-5-chloro-2-ethoxy-3-hydroxybenzoic acid ( 6 ), which has served a benzoic acid part of the metabolites 4 and 5 , is described. Treatment of methyl 3-amino-4-substituted amino-5-chloro-2-ethoxybenzoate derivatives 11a-c with sodium nitrate in acidic medium gave the benzotriazole derivatives 13x,y instead of the objective 3-hydroxy counterpart. The synthesis of 7 started from o-vanillin acetate ( 15 ) and proceeded through the intermediates 2-hydroxy-3-methoxy-4-nitrobenzaldehyde ( 18 ), methyl 4-amino-2,3-dihydroxybenzoate ( 23 ), and methyl 7-hydroxy-2(3H)-benzoxazolone-6-carboxylate ( 30 ). Compound 30 was alternatively prepared from 23 via methyl 4-ethoxycarbonylamino-2-ethoxycarbonyloxy-3-hydroxybenzoate ( 29 ), which is the product resulting from the migration of the ethoxycarbonyl group of methyl 4-amino-2,3-diethoxycar-bonyloxybenzoate ( 27 ).     

New Monoterpene-Substituted Dihydrochalcones from Piper aduncum

Five New unusual monoterpene-substituted dihydrochalcones, the adunctins A–E (1″S)-1-{2′-hydroxy-4′-methoxy-6′-[4″-methyl-1″-(1?-methylethyl)cyclohex-3″ -en-1″ -yloxy]phenyl}-3-phenylpropan-1-one ( 1 ), (5aR*,8R*,9aR*)-3-phenyl-1-[5′,8′,9′,9′a-tetrahydro-3′-hydroxy-1′-methoxy-8′-(1″-methylethyl)-5′-a-methyldibenzo-[b,d]furan-4′-yl]propan-1-one ( 2 ), (2′R*,4″S*)-1-{6′-hydroxy-4′-methoxy-4″-(1?-methylethyl)spiro[benzo[b]-furan-2′(3′H),1″ -cyclohex-2″ -en]-7′-yl}-3-phenylpropan-1-one ( 3 ), (2′R*,4″R*)-1-{6′-hydroxy-4′-methylethyl-4″-(1?-methylethyl)spiro[benzo[b]furan-2′(3′H),1″-cyclohex-2″-en]-7′-yl}-3-phenypropan-1-one ( 4 ), and (5′aR*,6′S*, 9′R*,9′aS*)-1-[5′a,6′,7′,8′,9′a-hexahydro-3′,6′-methoxy-6′-methyl-9′-(1″-methylethyl)dibenzo[b,d]-furan-4′-yl]-3-phenylpropan-1-one ( 5 ) were isolated from the leaves of Piper aduncum (Piperaceae) by preparative liquid chromatography. In addition, (?)-methyllindaretin ( 6 ), trans-phytol, and α-tocopherol ( = vitamin E) were also isolated and identified. The structures were elucidated by spectroscopic methods, including 1D- and 2D-NMR spectroscopy as well as single-crystal X-ray diffraction analysis. The antibacterial and cytotoxic potentials of the isolates were also investigated.     

New 2-methyl-6-alkylamino-5,8-quinolinequinones and 1,2,3,4-tetrahydro derivatives

The syntheses of six new 2-methyl-6-alkylamino-5,8-quinolinequinones, three 1,2,3,4-tetrahydro-5,8-quinolinequinones, and 7-(2′,6′,10′-trimethylundecyl)-6-hydroxy-5,8-quinolinequinone are described as potential antimetabolites of coenzyme Q and as potential antimalarial agents. The six 2-methyl-6-alkylamino-5,8-quinolinequinones were prepared by a six-step synthesis. 2-Methyl-6-methoxy-8-nitroquinoline was prepared from 2-nitro-4-methoxyaniline and crotonaldehyde by a Skraup reaction. Raney nickel reduction gave 2-methyl-6-metboxy-8-aminoquinoline, which upon diazotization followed by dithionite reduction yielded 2-methyl-6-methoxy-5,8-diaminoquinoline. Subsequent dichromate oxidation gave 2-methyl-6-methoxy-5,8-quinolinequinone, which yielded the corresponding 2-methyl-6-alkylamino-5,8-quinolinequinone in good yield when treated with the appropriate alkylamine. The telrahydro-5,8-quinolinequinones were prepared by catalytic hydrogenation of the appropriate 5,8-quinolinequinones at elevated H₂ pressure followed by air oxidation of the reduction product. 7-(2′,6′,10′-Trimethylundecyl)-6-hydroxy-5,8-quinolinequinone was synthesized by radical alkylation of 6-hydroxy-5,8-quinolinequinone by thermal decomposition of di-3,7,11-trimethyldodecanoyl peroxide, which was prepared by a multistep procedure from farnesol. Of the five new 2-methyl-6-alkylamino-5,8-quinoline-quinones tested against P. berghei in mice (blood schizonticidal test), only 2-methyl-6-cycloheptylamino-5,8-quinolinequinone was active (T-C = 6.1 at 320 mg./kg.). Both 7-(2′,6′,10′-trimelhytundecyl)-6-hydroxy-5,8-quinolinequinone and the tetrahydro derivatives were inactive in this same test system.     

Streptonigrin and lavendamycin partial structures. Preparation of 7-amino-2-(2′-pyridyl)quinoline-5,8-quinone-6′-carboxylic acid: A probe for the minimum,potent pharmacophore of the naturally occurring antitumor-antibiotics

The preparation of 7-amino-2-(2′-pyridyl)quinoline-5,8-quinone-6′-carboxylic acid (4) constituting a potential minimum, potent pharmacophore of streptonigrin (1) and lavendamycin (2) , two structurally-related naturally-occurring antitumor-antibiotic, is detailed. In contrast to observations associated with streptonigrin and lavendamycin in which the C-6′ acid potentiates the antitumor, antimicrobial, and cytotoxic activity of the naturally-occurring, substituted 7-aminoquinoline-5,8-quinone AB ring systems, the C-6′ carboxylic acid of 4 diminishes the observed antimicrobial and cytotoxic properties of 7-amino-2-(2′-pyridyl)quinoline-5,8-quinone.     

Intramolecular substitution of unactivated aryl groups by thioamide anion

The general reaction of intramolecular nucleophilic substitution of unactivated aryl groups by thioamide anion in dipolar aprotic amide solvent is extended by the syntheses of 6-chloro-5-methoxy-2-methylbenzothiazole from 2′,4′-dichloro-5′-methoxythioacetanilide and 6-methoxy-2-methylbenzothiazole from 4′-methoxy-2′-nitrothioacetanilide. The six-membered fused ring heterocycles, 2-methyl-4H,3-benzothiazine and 6,8-dichloro-3-rnethyl-1H-4,1,2-benzothiadi-azine are also prepared.     

SYNTHESIS OF NEW 8-METHOXY-4-METHYL-3-(N-[2′-AMINO-(1′,3′,4′)THIA/OXA-DIAZOL-5′-YL]-SUBSTITUTED METHYL)-AMINO THIOCOUMARINS

8-Methoxy-4-methyl-3-(N-[2′-amino-(1′, 3′,4′)thia/oxa-diazol-5′-yl] substituted methyl)-amino thiocoumarins 6(a–f) and 7(a–f), were synthesized by using the unreported 8-methoxy-4-methyl-3-[N-(2′-oxo-2′-methoxy-1′-substituted ethan-1′-yl) amino thiocoumarins as key intermediates.     

Synthesis of 1-functionalized-6-hydroxy-4-methyl and 6,11-dihydroxy-4-methylnaphtho[2,3-g]isoquinoline-5,12-quinones

Using 2-methoxy- and 2,5-dimethoxyacetophenones 8a and 8b as starting materials, 1-chloro-4-methylisoquinoline-5,8-quinone ( 6 ) and its 6-bromo derivative 7 were obtained via multistep sequences. Whereas Diels-Alder condensation of the former compound with homophthalic anhydride ( 22 ) led to a mixture of the two possible isomers: 1-chloro-11-hydroxy-4-methylnaphtho[2,3-g]isoquinoline-5,12-quinone ( 23 ) and 1-chloro-6-hydroxy-4-methylnaphtho[2,3-g]isoquinoline-5,12-quinone ( 24 ), this last tetracyclic chloroquinone was specifically obtained from 6-bromo-1-chloro-4-methylisoquinoline-5,8-quinone ( 7 ) and homophthalic anhydride. The 6,11-dihydroxy derivative was then prepared by ammonium nitrate oxidation or photochemically by cycloaddition of benzocyclobutenedione ( 28 ) and 1-chloro-4-methylisoquinoline-5,8-quinone ( 6 ). Chloro compounds were easily substituted by diamines to provide corresponding 1-amino substituted hydroxy tetracyclic quinones.     

Sur l'orientation et les anomalies de l'acetylation des Bz-méthoxy nitro-2 benzofurannes

4-Methoxy-, 5-methoxy- and 7-methoxy-2-nitrobenzofurans have been acetylated via the Friedel-Crafts reaction under the same reaction conditions. 2-Nitrobenzofuran does not undergo acetylation while 6-methoxy-2-nitrobenzofuran only produces decomposition products. As a result of the positive acetylation reactions, 7-acetyl-4-methoxy-, 4-acetyl-5-methoxy- and 4-acetyl-7-methoxy-2-nitrobenzofuran have been prepared. As side products in the acetylation reactions, 4-methoxy-3-(4′-methoxy-2′-nitro-7′-benzofuranyl)-2,3-dihydrobenzofuran-2-one was isolated when 4-methoxy-2-nitrobenzofuran was the starting material and, likewise, when 5-methoxy-2-nitrobenzofuran was the starting material, 3-chloro-5-methoxy-2,3-dihydrobenzofuran-2-one was obtained. Furthermore, 5-methoxy-2-nitrobenzofuran participated in an unexpected chlorination leading to 4-chloro-5-methoxy-2-nitrobenzofuran.     

Preparative separation of six coumarins from the pummelo (Citrus maxima (Burm.) Merr. Cv. Shatian Yu) peel by high-speed countercurrent chromatography

In this work, six coumarins, including two new ones, 8-(3-hydroxy-2,2-dimethylpropyl)-7-methoxy-2H-chromen-2-one (2) and 5-[(7′,8′-dihydroxy-3′,8′-dimethyl-2-nonadienyl)oxy] psoralen (4), as well as four known ones, 5-[(6′,7′-dihydroxy-3′,7′-dimethyl-2-octenyl) oxy] psoralen (1), marmin (3), epoxybergamottin (5), and aurapten (6) were successfully separated from the crude extract of pummelo (Citrus maxima (Burm.) Merr. Cv. Shatian Yu) peel by high-speed countercurrent chromatography in a single run with petroleum-ether–ethyl acetate–methanol–water (4:6:6:4, v/v). The structures of these six coumarins were elucidated by ESI-MS, extensive 1D and 2D NMR spectroscopy.     

A new synthesis of methoxalen

A new seven step synthesis of methoxalen, 9-methoxy-7H-furo[3,2-g][1]benzopyran-7-one, starting from 2-chloro-2′-hydroxy-3′,4′-dimethoxyacetophenone is described. The yields in every step are good (60-100%).     

Synthesis and properties of 5-(1,2-dihaloethyl)-2′-deoxyuridines and related analogues

The regiospecific reaction of 5-vinyl-3′,5′-di-O-acetyl-2′-deoxyuridine ( 2 ) with HOX (X = Cl, Br, I) yielded the corresponding 5-(1-hydroxy-2-haloethyl)-3′,5′-di-O-acetyl-2′-deoxyuridines 3a-c . Alternatively, reaction of 2 with iodine monochloride in aqueous acetonitrile also afforded 5-(1-hydroxy-2-iodoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 3c ). Treatment of 5-(1-hydroxy-2-chloroethyl)- ( 3a ) and 5-(1-hydroxy-2-bromoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 3b ) with DAST (Et₂NSF₃) in methylene chloride at -40° gave the respective 5-(1-fluoro-2-chloroethyl)- ( 6a , 74%) and 5-(1-fluoro-2-bromoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 6b , 65%). In contrast, 5-(1-fluoro-2-iodoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 6e ) could not be isolated due to its facile reaction with methanol, ethanol or water to yield the corresponding 5-(1-methoxy-2-iodoethyl)- ( 6c ), 5-(1-ethoxy-2-iodoethyl)- ( 6d ) and 5-(1-hydroxy-2-iodoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 3c ). Treatment of 5-(1-hydroxy-2-chloroethyl)- ( 3a ) and 5-(1-hydroxy-2-bromoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 3b ) with thionyl chloride yielded the respective 5-(1,2-dichloroethyl)- ( 6f , 85%) and 5-(1-chloro-2-bromoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 6g , 50%), whereas a similar reaction employing the 5-(1-hydroxy-2-iodoethyl)- compound 3c afforded 5-(1-methoxy-2-iodoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 6c ), possibly via the unstable 5-(1-chloro-2-iodoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine intermediate 6h . The 5-(1-bromo-2-chloroethyl)- ( 6i ) and 5-(1,2-dibromoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 6j ) could not be isolated due to their facile conversion to the corresponding 5-(1-ethoxy-2-chloroethyl)- ( 6k ) and 5-(1-ethoxy-2-bromoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 61 ). Reaction of 5-(1-hydroxy-2-bromoethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 3b ) with methanolic ammonia, to remove the 3′,5′-di-O-acetyl groups, gave 2,3-dihydro-3-hydroxy-5-(2′-deoxy-β-D-ribofuranosyl)-furano[2,3-d]pyrimidine-6(5H)-one ( 8 ). In contrast, a similar reaction of 5-(1-fluoro-2-chloroethyl)-3′,5′-di-O-acetyl-2′-deoxyuridine ( 6a ) yielded (E)-5-(2-chlorovinyl)-2′-deoxyuridine ( 1b , 23%) and 5-(2′-deoxy-β-D-ribofuranosyl)furano[2,3-d]pyrimidin-6(5H)-one ( 9 , 13%). The mechanisms of the substitution and elimination reactions observed for these 5-(1,2-dihaloethyl)-3′,5′-di-O-acetyl-2′-deoxyuridines are described.     

5a-Carba-β-D-, 5a-Carba-β-L- and 5-Thio-β-L-xylopyranosides as New Orally Active Venous Antithrombotic Agents

Mitsunobu displacement of (−)-(1S,4R,5S,6S)-4,5,6-tris{[(tert-butyl)dimethylsilyl]oxy}cyclohex-2-en-1-ol ((−)- 12 ; a (−)-conduritol-F derivative) with 4-ethyl-7-hydroxy-2H-1-benzopyran-2-one ( 16 ) provided a 5a-carba-β-D -pyranoside (+)- 17 that was converted into (+)-4-ethyl-7-[(1′R,4′R,5′S,6′R)-4′,5′,6′-trihydroxycyclohex-2′-en-1′-yloxy]-2H-1-benzopyran-2-one ((+)- 5 ) and (+)-4-ethyl-7-[(1′R,2′R,3′S,4′R)-2′,3′,4′-trihydroxycyclohexyloxy]-2H-1-benzopyran-2-one ((+)- 6 ). The 5a-carba-β-D -xyloside (+)- 6 was an orally active antithrombotic agent in the rat (venous Wessler's test), but less active than racemic carba-β-xylosides (±)- 5 and (±)- 6 . The 5a-carba-β-L -xyloside (−)- 6 was derived from the enantiomer (+)- 12 and found to be at least 4 times as active as (+)- 6 . (+)-4-Cyanophenyl 5-thio-β-L -xylopyranoside ((+)- 3 ) was synthesized from L -xylose and found to maintain ca. 50% of the antithrombotic activity of its D -enantiomer. Compounds (±)- 5 , (±)- 6 , and (−)- 6 are in vitro substrates for galactosyltransferase 1.     

Synthesis of Tri- and Disalicylaldehydes and Their Chiral Schiff Base Compounds

A suitable procedure for convenient preparation of 1,3,5-tris(4-hydroxy-5-formylphenyl)benzene (6) was exploited via 5-bromosalicylaldehyde as starting reactant. Among the obtained products, compound 6, 4-methoxy-3-formylphenylboronic acid (9), 1,3,5-tris(4-methoxy-5-formylphenyl)benzene (10), and 4-methoxy-4′-hydroxyl-3,3′-diformyl-1,1′-diphenyl (11) had not been reported previously. Two new chiral Schiff base ligands, L1 and L2, were obtained from the tri- or disalicylaldehydes.     

Synthesis of 4-methoxy-3,5-dinitrobenzaldehyde: a correction to supposed tele nucleophilic aromatic substitution

1,3-Dinitro-5-trichloromethylbenzene (2) was reacted with sodium methoxide in an attempt to prepare 4-methoxy-3,5-dinitrobenzaldehyde (7) via a reported tele nucleophilic aromatic substitution. The product from this reaction was methyl 3,5-dinitrobenzoate (5) and not the methoxy aldehyde as had been reported. The desired product was prepared by conventional nitration methodology from 4-methoxy-3-nitrobenzaldehyde.     

Structure and reactions of a thiazolino[3,2-a]pyrimidine carbinolamine

Ethyl 4-chloroacetoacetate condenses with 4-amino-6-hydroxy-2-pyrimidinethiol to yield ethyl 3-hydroxy-5-oxo-7-aminothiazolino[3,2-a]pyrimidin-3-acetate ( 3 ), and not ethyl 3-hydroxy-5-amino-7-oxothiazolino[3,2-a]-pyrimidin-3-acetate, as previously reported. This compound reacts with ammonia to produce ethyl 4-(6′-amino-4′-oxo-2′-pyrimidinethiol)-3-aminocrotonate ( 8 ), the open chain structure of which accounts for the cyclization of 3 to the poly-cyclic lactam, 6a-hydroxy-5,6,6a,7-tetrahydro-8-thia-1,4-diazacycl[3.3.2]azine-2,5-dione, rather than the sterically more favorable lactone, when 3 was treated with triethylamine. Some other reactions of 3 are described, and the structures of 3 and 8 were comfirmed by single crystal X-ray diffraction analysis.     

Preparation,proton and carbon-13 structure determination,and fungicidal activity of chlorinated 1-arylamino-1H-pyrrole-2,5-diones

1-(2′,4′-dichloro)phenylamino-1H-pyrrole-2,5-dione and 1-(2′,4′,6′-trichloro)phenylamino-1H-pyrrole-2,5-dione were prepared via direct chlorination of 2-phenyl-3-oxo-6-hydroxy-2H-pyridazine. Both pmr and mass spectroscopy clearly showed that dichloro substitution occurred in the aromatic moiety and not in the vinylic region of the molecule. The former method showed that pyridiazine- to pyrrole-ring isomerization had occurred already at the level of dichlorination. The identical 2′,4′-dichlorophenyl and 2′,4′,6′-trichlorophenylpyr-rolediones were also prepared by reaction of maleic anhydride with the appropriate arylhydrazine. Similar 2′,4-dichlorophenyl and 2′,4′,6′-trichlorophenyl analogues were prepared using dichloromaleic anhydride. Cmr spectroscopic techniques were used for pyridazine-/pyrrole-ring stereochemical assignment of products derived from dichloromaleic anhydride. 1-(2′,4′-dichloro)phenylamino-1H-pyrrole-2,5-dione and the trichloro-phenyl analogue were shown to exhibit fungicidal activity in both in-vivo and in-vitro assays.     

Six podocarpane-type trinorditerpenes from the bark of Taiwania cryptomerioides

Six podocarpane-type trinorditerpenes were isolated from the bark of Taiwania cryptomerioides. Their structures, 14-hydroxy-13-methoxy-8,11,13-podocarpatrien-7-one (1), 13-hydroxy-12-methoxy-8,11,13-podocarpatriene (2), 12-hydroxy-13-methoxy-8,11,13-podocarpatriene (3), 14-hydroxy-13-methoxy-8,11,13-podocarpatriene (4), 13-hydroxy-8,11,13-podocarpatriene (5), and 13,14-dihydroxy-8,11,13-podocarpatrien-7-one (6), were determined principally from spectral evidence.     

Reaction of ethyl γ-bromo-β-methoxycrotonate with carbonyl compounds. Synthesis of 4-methoxy-6-substituted-5,6-dihydro-2H-pyran-2-ones and 3-substituted 3-pyrazolin-5-ones

Ethyl β-methoxycrotonate I reacts with substituted carbonyl compounds II in benzene to give 4-methoxy-6-substituted-5,6-dihydro-2H-pyran-2-ones III. The reaction of IIIa and j with hydrazine hydrate in ethanol leads to 3-[(1′-thienyl-1-hydroxy)methyl]-5-hydroxy-1H-pyrazole (IVa) and 3-[1′-styryl-1′-hydroxy)methyl]-5-hydroxy-1H-pyrazole (IVj) in good yields. The structure of the products were assigned and confirmed on the basis of their elemental analysis and the electronic absorption, infrared and nmr spectra.     

Constituents of Flowers of Murraya Paniculata

Three new coumarins, yuehgesin-A (1), -B (2) and -C (3) and 22 compounds—murracarpin (4), mupanidin (5), isomeranzin (6), murralongin (7), scopoletin (10), 7-methoxy-8-(l′-ethoxy-2′-hydroxy-3′-methyl-3′-butenyl)coumarin (11), umbelliferone (12), paniculatin (13), braylin (14), auraptenol (15), meranzin hydrate (16), minumicrolin (17), scopolin (18), caffeine (19), 3,3′,4′,5,5′,6,7-heptamethoxyflavone (20), 4-hy-droxybenzaldebyde (21), p-hydroxybenzoic acid (22), cis- and trans-ferulic acid (23), cis- and transmethyl ferulate (24) and trans-ethylferulate (25)—were isolated and characterized from fresh flowers of Murraya paniculata collected in Taiwan. Their structures were elucidated by spectral methods. The chemotaxonomy of Murraya paniculata is, discussed.