Studies in oxasteroids—I : Synthesis of 3-cyano-3-methyl-7-methoxychroman-4-one and the structure of an “abnormal” product

A synthesis of 3-cyano-3-methyl-7-methoxychroman-4-one is reported. The structure of an “abnormal” product obtained during isomerization (III) with potassium t-butoxide in t-butanol, followed by alkylation with methyl iodide has been proved to be 3-t-butoxy-2-cyano- 2-mehthyl-2′,4′-dimethoxypropiophenone (IVa).

A revised structure for the condensation product of 2-carbethoxycyclopentanone and ethyl cyanoacetate

The condensation product of 2-carbethoxycyclopentanone and ethyl cyanoacetate is ethyl 2-carbethoxycyclopentylidene cyanoacetate (IIa) and not the one described by Kon and Nanji. Similarly, 2-carbomethoxycyclopentanone and methyl cyanoacetate yield methyl 2-carbomethoxycyclopentylidene cyanoacetate (IIb). The by-products obtained in the first reaction are cyclopentylidene cyanoacetate (IV) and the enamine of 2-carbethoxycyclopentanone (VIa).

Studies in sesquiterpenes—XXVI : Synthesis of 2,2,6-trimethyl-3-oxo-1-carbomethoxybicyclo[0,3,3]octane, a degradation product of patchouli alcohol

The synthesis of the title compound is described and results of some experiments on the degradation of patchouli alcohol are reported.

Synthetic investigations in the sesamin group - Part I. Synthesis of samin, a degradation product of sesamolin

Ethylα-bromovinylacetate (VII) was condensed with the sodio derivative of ethyl piperonoylacetate (VIII) to give diethylα-vinyl-α′-piperonoylsuccinate (IX). The latter on reduction with lithium aluminium hydride furnished the triol (X), which underwent smooth cyclisation with 1% ethanolic hydrogen chloride to 2-(3′, -methylenedioxyphenyl)-hydroxymethyl-4-vinyltetrahydrofuran (XIa). The structure of XIa was established by Oppenauer oxidation to an aldehyde. Ozonolysis of XIa afforded samin (I).

Synthesis of 1,3-dimethyl-1,3-dicarboxycyclohexane-2-acetic acid. An isomer of the degradation product of abietic acid

A synthesis of 1,3-dimethyl-1,3-dicarboxycyclohexane-2-acetic acid has been described, and proved to be an isomer of the C12-acid-an oxidative degradation product of abietic acid.

Reaction of dialkyl 2-butynoate with aniline and formaldehyde: revision of the structure of the product

Dimethyl 3-(aryl)-3,6-dihydro-2H-1,3-oxazine4,5-dicarboxylate structure assigned for the products obtained in the Bronsted acid catalyzed reaction of dimethyl but-2-ynoates with anilines and an excess of formaldehyde in methanol has been revised to methyl 1-(aryl)-3-(methoxymethyl)-4,5-dioxopyrrolidine-3-carboxylate. (C) 2010 Elsevier Ltd. All rights reserved.

Mechanism of hydroxylation of aromatic compounds: II. Evidence for the involvement of superoxide anions in enzymatic hydroxylations

The mechanism of hydroxylation reactions catalyzed by m-hydroxybenzoate-4-hydroxylase and anthranilate hydroxylase from Aspergillus niger was investigated using superoxide dismutase from ovine erythrocytes. Inclusion of superoxide dismutase in the assay mixtures of the two enzymes resulted in complete inhibition of the hydroxylation reaction, indicating the possible involvement of superoxide anions (O2−) in these reactions.

Mechanism of hydroxylation of aromatic compounds: Evidence for the involvement of superoxide anion in a model system

Hydroxylation of aromatic compounds was observed in NADH-phenazine methosulfate-O2 model system known to generate superoxide anions (Image ). Addition of superoxide dismutase prepared from ovine erythrocytes to this hydroxylating system resulted in complete inhibition, suggesting an involvement of Image in aromatic hydroxylations.

An Eventful Synthetic Approach Towards the Biologically Potent Natural Product Ottelione A: Enantio-, Regio- and Stereoselective Construction of the Bicyclic Core

A novel synthetic approach towards the recently reported anti-tumor and anti-tuberculor natural product ottelione A from the readily available Diels-Alder adduct of cyclopentadiene and p-benzoquinone is delineated. Our short strategy, besides being enantio-, regio- and stereoselective, charts an eventful course and is inherently well-suited for adaptation towards diverse synthetic analogues of this biologically potent natural product.

Polarization Caging in Diffusion-Controlled Electron Transfer Reactions in Solution

In some bimolecular diffusion-controlled electron transfer (ET) reactions such as ion recombination (IR), both solvent polarization relaxation and the mutual diffusion of the reacting ion pair may determine the rate and even the yield of the reaction. However, a full treatment with these two reaction coordinates is a challenging task and has been left mostly unsolved. In this work, we address this problem by developing a dynamic theory by combining the ideas from ET reaction literature and barrierless chemical reactions. Two-dimensional coupled Smoluchowski equations are employed to compute the time evolution of joint probability distribution for the reactant (P-(1)(X,R,t)) and the product (p((2))(X,R,t)), where X, as is usual in ET reactions, describes the solvent polarization coordinate and R is the distance between the reacting ion pair. The reaction is described by a reaction line (sink) which is a function of X and R obtained by imposing a condition of equal energy on the initial and final states of a reacting ion pair. The resulting two-dimensional coupled equations of motion have been solved numerically using an alternate direction implicit (ADI) scheme (Peaceman and Rachford, J. Soc. Ind. Appl. Math. 1955, 3, 28). The results reveal interesting interplay between polarization relaxation and translational dynamics. The following new results have been obtained. (i) For solvents with slow longitudinal polarization relaxation, the escape probability decreases drastically as the polarization relaxation time increases. We attribute this to caging by polarization of the surrounding solvent, As expected, for the solvents having fast polarization relaxation, the escape probability is independent of the polarization relaxation time. (ii) In the slow relaxation limit, there is a significant dependence of escape probability and average rate on the initial solvent polarization, again displaying the effects of polarization caging. Escape probability increases, and the average rate decreases on increasing the initial polarization. Again, in the fast polarization relaxation limit, there is no effect of initial polarization on the escape probability and the average rate of IR. (iii) For normal and barrierless regions the dependence of escape probability and the rate of IR on initial polarization is stronger than in the inverted region. (iv) Because of the involvement of dynamics along R coordinate, the asymmetrical parabolic (that is, non-Marcus) energy gap dependence of the rate is observed.

Involvement of heme in the transcriptional activation of CYPIIB1/B2 gene by phenobarbitone in rat liver—Studies with succinylacetone

Earlier studies in this laboratory had implicated heme to function as a positive modulator of phenobarbitonemediated activation of CYPIIB1/B2 gene transcription in rat liver. However, recent reports have indicated that succinylacetone, a specific inhibitor of δ-aminolevulinate dehydrase, does not affect this process. The present studies indicate that succinylacetone does inhibit the phenobarbitone-mediated increase in CYPIIB1/B2 mRNAs and their transcription in rat liver at early time points (45 min to 3 h), but the inhibition is not pronounced at later time points (16 h). Succinylacetone is a weaker inhibitor of heme biosynthesis than CoCl2, 3-amino-1,2,4-triazole, or thioacetamide used earlier in this laboratory. Succinylacetone induces δ-aminolevulinate synthase, whereas the other compounds depress the levels of the enzyme. There is a good correlation between the amount of freshly synthesized nuclear heme pool and the activation of CYPIIB1/B2 transcription by phenobarbitone. A model implicating a nuclear heme pool regulating the transcription of δ-aminolevulinate synthase, CYPIIB1/ B2, and heme oxygenase genes is proposed.