Synthesis of (5R*)- and (5S*)-5,7,11-trimethyl-3a-phenyl-4,5-dihydro-3aH-1,4-methano[1,3]oxazolo[3,2-a]quinolin-2-ones

Heating of N-benzoyl-N-[2-(1-methylbut-2-en-1-yl)-4-methylphenyl]glycine with ethyl chloroformate or acetic anhydride gave (5R*) and (5S*) isomers of (1R*,3aS*,4S*,11S*)-5,7,11-trimethyl-3a-phenyl-4,5-dihydro-3aH-1,4-methano[1,3]oxazolo[3,2-a]quinolin-2-one.     

Reactions of N- and C-alkenylanilines: IX. Synthesis, oxidation, and nitration of some 7-methyl-1,3a,4,8b-tetrahydrocyclopenta[b]indoles

Heating of 4-acyl-3-iodo-7-methyl-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indoles in piperidine gave 4-acyl-7-methyl-1,3a,4,8b-tetrahydrocyclopenta[b]indoles which were oxidized with KMnO4 to obtain the corresponding 4-acyl-7-methyl-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indole-1,2-diols. Oxidation of 4-acyl-7-methyl-1,3a,4,8b-tetrahydrocyclopenta[b]indoles at the olefinic double bond with hydrogen peroxide in acetonitrile in the presence of formic acid afforded stereoisomeric epoxides with cis and trans orientation of the nitrogen-containing and oxirane rings. Nitration with a mixture of ammonium nitrate and trifluoroacetic anhydride produced 5-nitro derivatives. The structure of 1-{(1aR*,1bR*,6bS*,7aS*)-5-methyl-1a,1b,2,6b,7,7ahexahydrooxireno[4,5]cyclopenta[1,2-b]indol-2-yl}ethanone was determined by X-ray analysis.     

Regioselectivity in the formation of norbornene-fused pyrazoles: preparation of 1-substituted derivatives of 4,5,6,7-tetrahydro-1H-4,7-methanoindazole

The structural characteristics of (±)-(exo,exo)-3-(hydroxymethylene)-5,6-(isopropylidenedioxy)bicyclo[2.2.1]heptan-2-one make the reactions between this β-diketone and hydrazines particularly interesting for elucidating the mechanism of pyrazole formation. The isolation and X-ray structure determination of two 5-hydroxy substituted Δ²-pyrazolines [(±)-(3aR*,4R*,5R*,6S*,7R*,7aR*)-7a-hydroxy-5,6-(isopropylidenedioxy)-3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-indazole] and [(±)-(3aS*,4R*,5R*,6S*,7R*,7aR*)-7a-hydroxy-5,6-(isopropylidene-dioxy)-1-phenyl-3a,4,5,6,7,7a-hexa-hydro-4,7-methano-1H-indazole] has been determinant for proposing a mechanism. Besides B3LYP/6-31G* calculations have been carried out on all intermediate dihydroxypyrazolidines and 5-hydroxypyrazolines. Finally, the annular tautomerism of the NH-methanotetrahydroindazoles has been studied both experimentally (¹³C NMR) and theoretically: the Mills-Nixon effect favours the 2H-tautomer.     

Diastereoselective 1,3-Dipolar Cycloaddition of Nitrones to 1<Emphasis Type="Italic">H</Emphasis>-Pyrrole-2,3-diones. Synthesis of pyrrolo[3,2-<Emphasis Type="Italic">d</Emphasis>]isoxazoles

1H-pyrrol-2,3-diones react with nitrones affording substituted pyrrolо[3,2-d]isoxazoles. The structures of ethyl (3R*,3aR*,6aR*)-6-benzyl-3-(4-bromophenyl)-4,5-dioxo-2,6a-diphenylhexahydro-3aHpyrrolo[ 3,2-d]isoxazole-3a-carboxylate and dimethyl (3R*,3aR*,6aS*)-3-(4-bromophenyl)-4,5-dioxo-2,6-diphenyltetrahydro-3aH-pyrrolo[3,2-d]isoxazole-3a,6a(4H)-dicarboxylate were proved by single-crystal X-ray analysis.     

Studies on ketene and its derivatives. CXI . Photoreaction of diketene with 2(1H)-quinolone derivatives

Photoreaction of diketene with 4-methyl-2(1H)-quinolone and 1,4-dimethyl-2(1H)-quinolone gave 2R*,2aR*,SbR*- and 2R*,2aS*8bS*-8b-methyl-3-oxo-1,2,2a,3,4,8b-hexahydrocyclobuta[c]quinoline-2-spiro-2′-(oxetan)-4′-one ( 6a and 6b ), and their 4-methyl derivatives 7a and 7b , respectively. Thermolysis of compounds 6 and 7 afforded 2aR*,8bS*-8b-methyl-2-methylene-3-oxo-1,2,2a,3,4,8b-hexahydrocyclobuta[c]quinoline ( 8 ) and its 4-methyl derivatives 9 , respectively. Similarly, photolysis of diketene and 4-acetoxy-2(1H)-quinolone gave 1R*,2aS*,8bS*- and 1R*,2aR*,8bR*-8b-acetoxy-3-oxo-1,2,2a,3,4,8b-hexahydrocyclobuta[c]-quinoline ( 11a and 11b ). Alcoholysis of compounds 11a and 11b with hydrogen chloride in methanol gave 1-hydroxy-1-(methoxycarbonyl)methylcyclobuta[c]quinoline derivative 12 and 13 which were transformed to 4-acetyl-3-methyl-2(1H)-quinolone ( 15 ) by further alcoholysis. Photoreaction of diketene with 2(1H)-quinolone derivatives gave the corresponding cyclobuta[c]quinoline spirooxetanone derivatives 18 and 23 , which, by thermolysis, were transformed to 2-methylenecyclobuta[c]quinoline 23 and 25 , respectively.     

Novel cembranolides (Coralloidolide D and E) and a 3,7-Cyclized cembranolide (Coralloidolide C) from the mediterranean coral Alcyonium coralloides

The Mediterranean alcyonacean Alcyonium (= Parerytkropodium) coralhides (PALLAS, 1766) is shown to contain three novel diterpenes which are of biogenetic significance: the 3,7-cyclized cembranoid Coralloidolide C ( = (+)-(6R*, 7R*, 11S*, 12aS* 3aE)-7,8-epoxy-3,5,6,7,8,9,10,11,12,12a-decahydro-12a-hydroxy-11-isopropenyl-1,4-dimethyl-3-oxocyciopentacydoundecene-8,6-carbolactone; (?)- 3 ), the O-bridged diketonic cembranolide Coralloidolide D (= (+)-(1R*, 2S*, 3R*, 5R*, 12S*, 8Z)-2,5-epoxy-1-hydroxy-12-isopropenyl-5,9-dimethyl-7,10-dioxocyclotetradeca-8-ene-1,3-carbolactone; (+)- 4 ), and the diketonic epoxycembranolide coralloidolide E (=(+)-(1R*, 2R*, 3R*, 12S*, 5Z, 8Z)-1,2-epoxy-12-isopropenyl-5,9-dimethyl-7,10-dioxocyclotetra-deca-5,8-diene-1,3-carbolactone; (+)- 5 ), The latter in pyridine at r. t. undergoes a double bond shift from C(4) = C(5) to C(4) = C(18) to give the isomer (?)- 7 . Structural assignments are mainly based on ID and 2D NMR and MS spectral data. Either corailoidolide A ((?)- 1 ) or the hypothetic unsaturated 1,4-diketone 9 can be envisaged as the precursors of all coralloidolides.     

New Sesquiterpenoids from Salvia castanea Diels f. tomentosa

Two new sesquiterpenoids, castanin A (= 4R*,5R*,5aS*,8S*,8aR*,8bR*)‐8‐formyl‐4,5,5a,6,7,8,8a,8b‐octahydro‐5,8b‐dihydroxy‐3,5a,8‐trimethyl‐2‐oxo‐2H‐indeno[4,5‐b]furan‐4‐yl acetate; 1 ) and castanin B (= 1aS*,6R*,6aS*,7aR*,9aR*)‐1a,2,6,6a,7a,8,9,9a‐octahydro‐1a,5,7a‐trimethylbisoxireno[4,5 : 8,9]cyclodeca[1,2‐b]furan‐6‐yl acetate; 2 ) were isolated from the aerial parts of Salvia castanea Diels f. tomentosa, together with two known compounds, oplophanone and 1β,6α‐dihydroxyeudesm‐4(14)‐ene. Their structures were elucidated by spectroscopic analyses and, in the case of 2 , also by X‐ray crystallography. Castanin A ( 1 ) represents a novel sesquiterpenoid, with a contracted ring A, derived from eudesmanolide. A possible biogenetic pathway is proposed.     

Packing in three cyclooctitol acetates

Three cyclooctitol derivatives, in the form of a tetraacetate, (1S*,2R*,3S*,4S*)‐2,3,4‐triacetoxycyclooctan‐1‐ylmethyl acetate, C₁₇H₂₆O₈, and two regioisomeric acetonide triacetates, (3aS*,4R*,8S*,9S*,9aS*)‐8,9‐diacetoxy‐2,2‐dimethylcyclooctano[d][1,3]dioxan‐4‐ymethyl acetate and (3aS,4R,7S,9R,9aS)‐7,9‐diacetoxy‐2,2‐dimethylcyclooctano[d][1,3]dioxan‐4‐ylmethyl acetate, both C₁₈H₂₈O₈, have been studied. The conformation of the cyclooctane ring in the three compounds is quite close to the boat–chair form of the parent hydrocarbon. Packing is effected through weak C—H...O and van der Waals contacts.     

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.     

Enantioselective syntheses of isoprostane and iridoid lactones intermediates by enzymatic transesterification

Crude Pseudomonas cepacia lipase (Amano PS-30) is a suitable biocatalyst for the kinetic resolution of the 1,2-cis-disubstituted cyclopentanoid building block (3aR*,4R*,6aS*)-(±)-4-hydroxymethyl-3,3a,4,6a-tetrahydrocyclopenta[b]furan-2-one through enantioselective transesterification. Enantiomerically enriched acetic acid (3aS,4S,6aR)-(+)-2-oxo-3,3a,4,6a-tetrahydro-2H-cyclopenta[b]furan-4-yl methyl ester was utilized in a formal synthesis of the iridoids (+)-isoiridomyrmecin and (−)-teucriumlactone.     

Synthesis of Pyrano[4′,3′:2,3]pyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]quinoxalines by Reaction of Aroylpyrroloquinoxalines with Alkyl Vinyl Ethers

Thermally induced [4 + 2]-cycloaddition of 3-aroylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones with alkyl vinyl ethers afforded mixtures of diastereoisomeric (5S*,6aR*)- and (5R*,6aR*)-5-alkoxy-3-aryl-5,6-dihydropyrano[ 4′,3′: 2,3]pyrrolo[1,2-a]quinoxaline-1,2,7(8H)-triones.     

Hydrolysis of 6,6-dimethyl-4,8-dioxo-5,7-dioxaspiro[2.5]octane-1,1,2,2-tetracarbonitrile

Hydrolysis of 6,6-dimethyl-4,8-dioxo-5,7-dioxaspiro[2.5]octane-1,1,2,2-tetracarbonitrile in aqueous dioxane in the presence of hydrogen bromide gave a mixture of 2,2,3,3-tetracyanocyclopropane-1-carboxylic acid and ammonium 3-cyano-4-dicyanomethylidene-5-oxo-4,5-dihydro-1H-pyrrol-2-olate. Hydrolysis of the same compound in the presence of sulfuric acid was accompanied by nitrogen migration and led to the formation of (1R*,2S*,3S*)-1,3-dicyanocyclopropane-1,2-dicarboxamide whose structure was proved by X-ray analysis.     

Efficient synthesis of new tricyclic pyrano[3,2-c]pyridine derivatives

Reaction between arylidenemalononitriles and acetoacetanilide in the presence of piperazine hydrate in methanol at room temperature affords new tricyclic pyrano[3,2-c]pyridine derivatives of (rac-1S*,2R*,3R*,7R*,8R*,11R*)-2,11-diaryl-4,10-diimino-8-methyl-5-phenyl-6-oxo-9-oxa-5-azatricyclo-[5.3.1.0^3,8]undecane-1,3-dicarbonitrile family in yields of 55–84%. The molecular structures of the products were confirmed by X-ray crystallography and NMR spectroscopy.     

Synthesis of (5S*,4aS*,7aS*)-5-hydroxyhexahydro-cyclopenta[c]pyran-3(1H)-one

(5S*,4aS*,7aS*)-5-Hydroxyhexahydrocyclopenta[c]pyran-3(1H)-one, the promising isoprostane building block, was synthesized using intramolecular [3+2] cycloaddition of silyl nitronate generated from 4-benzyloxy-3-nitroocta-2,7-diene on the key step.     

New Dolabellane Derivatives from the Brown Alga Dictyota pardalis

Reinvestigation of the brown alga Dictyota pardalis f. pseudohamata CRIBB led to the crystallization of 1 and to the isolation of the two new dolabellane derivatives 2 and 3 . X-Ray analysis of 1 and 2 , together with detailed 1D-and 2D-NMR studies on 2 and 3 , allowed their structures to be elucidated as (1R*,3S*,7S*,11R*,4Z)-dolabella-4,8(17), 12(18)-triene-3,7-diol ( 1 ), (1R*,3S*,4S*,7S*,8S*,11R*,14R*,12E)-3,4:7,8-diepoxydolabe11-12-ene-14, 18-diol ( 2 ), and (1R*,3S*,4S*,7S*,8S*,11R*,14R*)-3,4:7,8-diepoxy-l,4,8,12,12-pentamethylbicyclo[9. 3. 0]tetra-decan-14-ol( 3 ).     

Hetero-Diels–Alder Reaction of Aroylpyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]quinoxalinetriones with Styrene

Hetero-Diels–Alder reaction of 3-aroylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones with styrene afforded diastereoisomeric (5R*,6aR*)- and (5S*,6aR*)-3,5-diaryl-5,6-dihydropyrano[4′,3′:2,3]pyrrolo[1,2-a]-quinoxaline-1,2,7(8H)-triones.     

Synthesis and molecular structure of di(4-hydroxy-2,6-diisoborn-2-ylphenyl)methane

Di(4-hydroxy-2-{(1R*,2S*,4S*)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl}-6-{(1S*,2R*,4R*)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl})methane was synthesized by condensation of the meso-diastereomer of 2,6-diisobornylphenol with paraformaldehyde under acid catalysis. The product structure as a meso-forms was confirmed by XRD analysis.     

Synthesis of N-allyl- and N-acyl-2-vinylindoline

Heating a mixture of (2R*,3R*)- and (2R*,3S*)-2-[(1S*)-1-iodoethyl]-3,5-dimethyl-1-[(2-nitrophenyl) sulfonyl]indolines with N-isopropylpiperidine in xylene resulted in (2S*,3R*)-3,5-dimethyl-1-[(2-nitrophenyl) sulfonyl]-2-vinylindoline. The latter reacted with thiophenol to afford (2S*,3R*)-3,5-dimethyl-2-vinylindoline, whose reaction with allyl halides or acetyl bromide gave rise to N-allyl-, N-propenyl-, or N-acetyl derivatives. Nitration of 1-acetyl-3,5-dimethyl-2-vinylindoline yielded ortho-nitro derivative.     

Novel Trinor-eremophilanes (Dendryphiellin B,C, and D), Eremophilanes (Dendryphiellin E,F, and G), and Branched C9-Carboxylic Acids (Dendryphiellic Acid A and B) from the Marine Deuteromycete Dendryphiella salina (SUTHERLAND) PUGHet NICOT

Further investigation of global extracts from cultures of the marine deuteromycete Dendryphiella salina leads to the isolation of three novel trinor-eremophilanes esterified by branched C₉-carboxylic acids, dendryphiellin B (= (+)-(1R*,2S*,7R*,8aR*)-1,2,6,7,8,8a-hexahydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6R*, 2E, 4E)-6-hydroxy-6-methylocta-2,4-dienoate; (+)- 2 ), dendryphiellin C (=(+)-(1R*, 2S*, 7R*, 8aR*)-1,2,6,7,8,8a-hexa-hydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6S, 2E, 4E)-6-methylocta-2,4-dienoate; (+)- 3 )), and dendryphiellin D (=(+)-(1R*, 2S*, 7R*, 8aR*)-1,2,6,7(8,8a-hexahydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6R*,2E,4E)-6-(hydroxymethyl)octa-2,4-dienoate; (+)- 4 ). An intact eremophilane, dendryphiellin E ( 5 ), and its ethanolysis product dendryphiellin F whose absolute configuration is represented by structural formula (+)- 6 are also isolated from the above extracts. Dendryphiellin E exists as an open form 5a in equilibrium with a closed form 5b . A similar equilibrium exists between the open form 8a and the closed form 8b of a non-esterified eremophilane, dendryphiellin G ( 8 ), which is isolated too from the above extracts and proves structurally related to the cyclic portion of 5 . Finally, the free, branched C₉-carboxylic acids dendryphiellic acid A ((+)- 9 ) and B ((+)- 10 ) which correspond to side chains of the above esterified terpenes are also isolated from the above extracts.     

Synthesis of 1′-substituted and 1′,3′-disubstituted (±)-2R*, 11bS*-9,10-Dimethoxy-1,3,4,6,7,11 b-Hexahydrospiro-[benzo[a]quinolizin-2,5′-imidazolidine]-2′,4′-diones

The results of the reaction between (±)-2R*,11bS*-2-alkyl(aryl)amino-1,3,4,6,7,11b-hexahydrobenzo[a]-quinolizine-2-carbonitriles 2 and isocyanates under a variety of experimental conditions are discussed. The ureides 3 and iminohydantoins 4 thus obtained were used to prepare N₃-monosubstituted and N₁,N₃-disubstituted derivatives of the (±)-2R*,11bS*-9,10-dimethoxy-1,3,4,6,7,11b-hexahydrospiro[benzo[a]quinolizin-2,5′-imidazolidine]-2′,4′-dione system 1 . The stereochemistry of these compounds is discussed, on the basis of spectroscopic evidence and study of their chemical reactivity.