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Three series of mesomorphic 2-acyloxy-5-phenylazotropones with alkoxy, alkyl, and alkoxycarbonyl groups at C-4 on the phenyl ring were prepared. It was known that the corresponding 5-phenylazotropolone derivatives and their methyl ethers were not mesomorphic. 2-Acetyl-5-(4-hexyloxyphenylazo)tropone, however, shows a monotropic smectic A phase. Even an acetyl group is therefore able to induce a mesophase. The effects of terminal substitution of the tropone ring by groups such as alkoxy, alkoxycarbonyl, and alkyl on the clearing points are discussed.

Cotylenins and fusicoccins, fungal diterpenoid glycosides, are know to have identical, yet unique, plant growth-regulating activities. These compounds widen the stomatal pore, stimulate cell enlargement, break seed dormancy, and stimulate rhizogenesis. Because of these plant-hormone like activities, fusicoccin, a representative of this family, has been widely utilized in plant physiology. During the course of our study on the structure-activity relationships of this class of compounds, 9-deoxy-15-hydroxycotylenol and its 15-methoxymethyl ether were synthesized in order to clarify the role of the 9α-hydroxy group of cotylenol, a common aglycon of cotylenins. Since these cotylenol analogs retained germination-stimulating activity on lettuce seeds, it has been clarified that the 9α-hydroxy group of cotylenol is not essential for its biological activities. This finding is informative in designing useful tools for targeting the 14-3-3 protein, which has recently been identified as the binding protein of fusico...

The rotational barriers of the exocyclic double bonds of a series of methyl 8-cyanoheptafulvene-8-carboxylates were measured to evaluate the steric effect and the contribution of the polarized structures. An incorporation of five-membered heterocycles lowered the activation energies sufficiently to allow the study of steric and electronic factors. Thus, the Type I compounds, 8-[cyano(methoxycarbonyl)methylidene]-2-methyl-8H-cyclohepta[b]furan and its sulfur and nitrogen analogues, which have a different extent of steric effect, had rates of rotation in the order of N > S > O. On the other hand, the Type II derivatives, 6-(1-cyano-1-methoxycarbonylmethylidene)-2-methylcyclohepta[b]furan and its sulfur and nitrogen analogues, for which the steric factor is unimportant, showed an order of N > O > S. This was also the case for the Type III derivatives, methyl 8-cyano-3-methoxyheptafulvene-8-carboxylate, methyl 8-cyano-3-(methylthio)heptafulvene-8-carboxylate, and methyl 8-cyano-3-(dimethylamino)heptafulvene-8...

The photocycloaddition of methyl 2,4-dioxopentanoate ( 1 ) to norbornadiene gave a diketo ester ( 4 ), derived from the expected [2 π +2 π ] cycloadducts, together with a [2 π +2 π +2 π ] cycloadduct ( 6 ), rearranged tricyclic ester ( 5 ), 7-substituted norbornene ( 7 ) and norbornadiene ( 8 ). The similar reaction of 1 with quadricyclane gave, 4, 5 and an oxetane ( 9 ), but no 7 . The occurrence of 5 signifies the formation of zwitter ions via an electron transfer process.

Cotylenol, one of the representative fusicoccane diterpenoids having 5-8-5-membered tricyclic carbon framework, is now synthesized for the first time via an eight-membered ring formation by an intramolecular ene reaction followed by an oxidative formation of the 8β,9α-glycol function on the central eight-membered ring.

In the photoaddition reaction of terpinolene with methyl 2,4-dioxopentanoate, the products derived from the tetrasubstituted C=C were four proto-[2+2] photocycloadducts, together with ene reaction products. When these proto-cycloadducts were treated with aqueous sodium carbonate, a facile retro-benzilic acid rearrangement to form substituted cyclopentenone derivatives occurred. The product from the other trisubstituted C=C was an ordinary retro-aldol product of the [2+2] cycloadduct and an ene reaction product. One of the proto-photocycloadducts was transformed into α-chamigren-3-one and further to α-chamigrene.

The high-pressure Diels–Alder reaction of fullerite with tropone and several of its derivatives under 300 MPa gave 1 : 1-[4 + 2] cycloadducts of C60 in good yields. Their 1H and 13C NMR spectra were consistent with the structures depicted. These compounds quantitatively regenerate starting materials upon thermolysis.

Based on biogenetic hypothesis, optically active plagiospirolides A and B (C35-terpenoids) have been synthesized by a Diels–Alder reaction between independently synthesized sesquiterpenoids (diplophyllolide A and diplophyllin) and a 5–8–5-membered tricyclic diterpenic hydrocarbon prepared from a CrCl2-mediated condensate of (3S)-benzyloxyirid-1-en-7-al and (3R)-7-chloroirid-1-ene.

Treatment of 2,3-dihydro-4aH-cyclohepta-1,4-dithiin with triphenylmethyl tetrafluoroborate followed by condensation with α-bromomalononitrile in pyridine afforded 5- and 7-(dicyanomethylene)-2,3-dihydrocyclohepta-1,4-dithiins in good yields. When changing the solvent to acetonitrile, the products obtained were 5- and 6-(2,2-dicyanoethyl)-2,3-dihydro-1,4-benzodithiins. This new method was applicable to the general synthesis of dicyanoheptafulvenes from tropylium salts.

Condensation of 2,7-dibromotropone and 7-bromo-4-isopropyl-2-(4-tolysulfonyloxy)tropone with oligoethylene glycol bis(2-mercaptoethyl) ethers gave sulfur-containing crown ether derivatives. Among these mercurophilic derivatives, triethylene glycol bis(2-mercaptoethyl) derivatives transport and extract mercury ion excellently.

Starting from the intramolecular [2+2] cycloaddition of 2,6-dimethyl-2-(3,4-dimethyl-3-cyclohexenyl)-4H-1,3-dioxin-4-one, (±)-valeranone, a cis-decalone sesquiterpenoid from Valeriana officinalis, was totally synthesized in stereoselective fashion.

A series of proto-photocycloadducts of methyl 2,4-dioxopentanoate to methylenecycloalkanes and -alkenes spontaneously caused retro-benzilic acid rearrangement in high yields. The results are utterly different from those of sterically-crowded acyclic alkenes, with which the rearrangement occurred by thermolysis as a minor process.

The high-pressure (to 10000 bar) Diels–Alder reaction of tropone with acrylonitrile showed temperature-dependent product distributions: at 80 °C, the product distribution was very similar to that obtained under atmospheric pressure to give four products, among which 9-endo-cyanobicyclo[3.2.2]nona-3,6-dien-2-one, in 38% yield, was the major product, while at room temperature there were only three products, i.e., 8-endo-, 9-endo-, and 9-exo-cyano derivatives. The absence of the 8-exo-cyano derivative might be due to an electrostatic repulsive interaction of cyano and carbonyl groups in the transition state geometry.

New liquid crystals with 2-benzoyloxy-2,4,6-cycloheptatrien-1-one (2-benzoyloxytropone) core were prepared. The [1,9] sigmatropic dynamic property in a 5-alkoxy-2-(4-alkoxybenzoyloxy)tropone structure was shown to play a decisive role in revealing mesophases by comparison with 5-alkoxy-2-(4-alkoxybenzyloxy)tropones and 7-bromo-5-dodecyloxy-2-(4-dodecyloxybenzoyloxy)tropone, which had no such molecular dynamic property. These liquid crystals showed varios phases, depending on the length of the alkyl chains.

Condensations of methyl cyanoacetate and 4-nitrobenzyl cyanide with 2-isopropyl-, 2-methyl-, and 2-phenyltropones in Ac2O gave isomeric 1-, 2-, and 3-substituted heptafulvene derivatives. The mechanism of reaction was explained in terms of a remote nucleophilic attack of the active methylene compounds to acetoxycycloheptatrienylium salt, followed by [1,5] sigmatropic hydrogen shift and elimination of acetic acid.

Treatment of 2,3-dihydro-4aH-cyclohepta-1,4-dithiin with triphenylmethyl tetrafluoroborate followed by condensation with α-bromomalononitrile in pyridine afforded 5- and 7-(dicyanomethylene)-2,3-dihydrocyclohepta-1,4-dithiins in good yields. When changing the solvent to acetonitrile, the products obtained were 5- and 6-(2,2-dicyanoethyl)-2,3-dihydro-1,4-benzodithiins. This new method was applicable to the general synthesis of dicyanoheptafulvenes from tropylium salts.

Based on biogenetic hypothesis, optically active plagiospirolides A and B (C35-terpenoids) have been synthesized by a Diels–Alder reaction between independently synthesized sesquiterpenoids (diplophyllolide A and diplophyllin) and a 5–8–5-membered tricyclic diterpenic hydrocarbon prepared from a CrCl2-mediated condensate of (3S)-benzyloxyirid-1-en-7-al and (3R)-7-chloroirid-1-ene.

1-(Tropon-2-yl)-1-aza-l5-crown-5 ether and 1-(7-bromotropon-2-yl)-1-aza-15-crown-5 ether were prepared by condensation of 1-aza-15-crown-5 ether and appropriate derivatives. Spectrophotometric titration of the 1:1-complexes of these crown derivatives showed a preferential complexation with lithium salt over other alkali metal salts. Thus, structural modification by capping with tropone system altered the selectivity.

Azulenequinones gave dimers when they were irradiated with a high-pressure mercury lamp. In polar solvents, head-to-head dimers were predominant, whereas head-to-tail dimers increased in less polar solvents. From 3-methoxy-1,5-azulenequinone, four products were obtained, while bromoazulenequinones and 1,5-azulenequinone gave a single dimer. The product distribution was dependent on the polarity of solvents, substituents, and concentrations.

Cotylenins and fusicoccins, fungal diterpenoid glycosides, are know to have identical, yet unique, plant growth-regulating activities. These compounds widen the stomatal pore, stimulate cell enlargement, break seed dormancy, and stimulate rhizogenesis. Because of these plant-hormone like activities, fusicoccin, a representative of this family, has been widely utilized in plant physiology. During the course of our study on the structure-activity relationships of this class of compounds, 9-deoxy-15-hydroxycotylenol and its 15-methoxymethyl ether were synthesized in order to clarify the role of the 9α-hydroxy group of cotylenol, a common aglycon of cotylenins. Since these cotylenol analogs retained germination-stimulating activity on lettuce seeds, it has been clarified that the 9α-hydroxy group of cotylenol is not essential for its biological activities. This finding is informative in designing useful tools for targeting the 14-3-3 protein, which has recently been identified as the binding protein of fusico...

The photoreaction of tropone 1 and electron-accepting 9,10-dicyanoanthracene (DCA) gave four products in less polar benzene while in more polar acetonitrile–dichloromethane (1∶1) solution an [8+4]π adduct was formed together with the above four products. The formation of the [8+4]π adduct was enhanced by biphenyl and quenched by 1,4-dimethoxybenzene. According to Weller’s equation, electron transfer from tropone 1 to DCA is estimated to be the endothermic (ΔG = +1.2 kcal mol–1). The following coupling reaction between DCA˙– and 1˙+ to the [8+4]π adduct, however, could make the electron-transfer process shift to generate the radical-ion pair.

[2+4]-[6+4] Cycloadducts were obtained from the thermal cycloaddition reactions of azulenequinones with cyclic 4π systems such as 1,3-diphenylisobenzofuran and isobenzofuran while the reaction of cycloheptatriene and azulenequinones gave ene products as well as cage molecules. The first addition site of 1,3-diphenylisobenzofuran was different for 3-bromoazulene-1,5-quinone and azulene-1,5-quinone; the former reacted on the cyclopentenone part and the latter on the C-6–C-7 bond to avoid formation of an unstable cyclopentadienone structure.

2-Alkenyl-6-methyl-4H-1,3-dioxin-4-ones, adducts of diketene to alkenals or alkenones, are useful synthons which are applicable to photocycloadditions to construct multiply-functionalized alicyclic compounds via stereoselective intramolecular path. Some of the cage-shaped photoproducts showed extraordinary spectroscopic features.

Several higher terpenoids having 5-8-5-membered tricyclic frameworks have been isolated from various kind of natural sources. For the total synthesis of this class of compounds, it is desirable that the synthetic strategy has a stereochemical flexibility, since the stereochemistries involving a basic carbon skeleton are quite different depending on the origins. Our synthetic scheme involves three key-steps, which are the dimerization of two iridoids getting B-seco derivatives, the Cope rearrangement of the condensates controlling the stereochemistry of C-11, and the ring-closure forming the central 8-membered ring. We finally accomplished the method to control the transition states in the second step with which any stereochemical combinations of C-6, C-11, and C-14 can be constracted freely. The versatility of this synthetic methodology has been proved by the total syntheses of stereochemically different type of terpenoids, such as ceroplastol II, dictymal, cycloaraneosene, and the diterpene potion of plagiospirolide.

The base-catalyzed rearrangement of bis- and tris(4-nitrobenzyloxy)tropones gave (α-hydroxy-4-nitrobenzyl)tropones through a Wittig-type mechanism. Only the 4-nitrobenzyloxy group adjacent to the c...

The high-pressure Diels–Alder reaction of tropones with 2–cyclopenten-1-one afforded isomeric mixtures of adducts. Upon UV irradiation, these adducts isomerized to hexahydro-as-indacene, via [1,3] acyl migration, and tetracyclo[7.3.0.03,7.06,8]undecene derivatives through a ketene intermediate via a di-π-methane rearrangement. The former tricyclic system corresponds to the carbon skeleton of ikarugamycin. An “exo [6+4] adduct” of tropone and 1,4-cyclopentadien-1-ol, an enol form of 2-cyclopentenone, was obtained as a by-product.

Photocycloaddition of 4-methyl-2-oxo-γ-valerolactone to cycloalkenes gave [2+2] cycloadducts, together with the ene reaction products. The stereostructures of photoproducts were identified by detailed NMR spectral analyses including NOE experiments. The photocycloadducts were convertible to (2-alkenylcycloalkyl)glyoxalic acids.

C 13 H 20 O 5 cristallise dans P1 avec a=7,535, b=9,472, c=10,927 A, α=104,631, β=103,430, γ=109,130°, Z=2; affinement jusqu'a R=0,045. La structure cristalline a une conformation symetrique C 1 comme une «selle»: l'angle d'intersection entre les 2 liaisons doubles est de 148,3° et l'atome oxygene du carbonyl est en dehors des 2 plans des liaisons doubles

The title compound, C15H20O4S2, crystallizes in a chiral space group although it contains mirror symmetry. The tropone ring is inclined at an angle of 50.3 (1)° to the crown ether ring. The planarity of the tropone ring system itself is diminished by as much as 20.8 (4)°.

Although thermal cycloaddition of tropone to ethoxyethene under ordinary pressure conditions is synthetically impractical, the reaction was greatly improved under 10000 bar to give six products with 95% conversion (1 bar=105 Pa): the major products obtained in 66% yield were 9α- and 9β-ethoxybicyclo[3.2.2]nona-3,6-dien-2-ones, Diels–Alder adducts, which were accompanied by other two 8-ethoxy derivatives and two [8+2] cycloadducts. 2-Methoxy- and 2-chlorotropones similarly gave better results under high-pressure conditions. The 13CNMR spectra of these Diels–Alder adducts provided useful information regarding structure elucidations.

Dictymal, a congener of epoxydictymene isolated from a brown alga, Dictyota dichotoma has been totally synthesized via a lactol-regulated oxy-Cope rearrangement of an appropriately designed dimer obtained from two C10-synthons (iridoids).

Bis(5-alkoxytropolonato)copper(II) complexes showed mesogenic properties. The corresponding zinc(II) complexes were not mesogenic although they have lower melting points than the copper complexes. The longer alkyl chains enhanced the appearance of highly ordered smectic phases and secondary alkyl chains reduced mesogenic properties.

2,5-Di(4-alkoxybenzoyloxy)tropones showed similar mesogenic properties to the corresponding benzenoids. The tropone carbonyl group, which behaved as a polar lateral substituent, enhanced the therma...

1-(Tropon-2-yl)-1-aza-l5-crown-5 ether and 1-(7-bromotropon-2-yl)-1-aza-15-crown-5 ether were prepared by condensation of 1-aza-15-crown-5 ether and appropriate derivatives. Spectrophotometric titration of the 1:1-complexes of these crown derivatives showed a preferential complexation with lithium salt over other alkali metal salts. Thus, structural modification by capping with tropone system altered the selectivity.

In 2-(2-alkenoyloxy)-5-alkoxytropones, showing a monotropic smectic A phase, the introduction of a double bond lowers the melting and clearing points as well as the recrystallization temperatures.