Biosynthesis of novel copolyesters containing 3-hydroxypivalic acid by Rhodococcus ruber NCIMB 40126 and related bacteria

Rhodococcus ruber and related Gram-positive bacteria synthesized and accumulated novel copolyesters containing 3-hydroxypivalic acid as constituent if the cells were cultivated in a mineral salts medium containing 3-hydroxypivalic acid and glucose as carbon sources. The copolyesters contributed 0.4–10% of the cellular dry mass, and they contained up to 78 mol% of 3-hydroxypivalic acid in addition to 3-hydroxybutyric acid and 3-hydroxyvaleric acid; a homopolyester of 3-hydroxypivalic acid was also synthesized under certain conditions. The presence of 3-hydroxypivalic acid in the accumulated copolyesters was confirmed by nuclear magnetic resonance spectrometry as well by coupled gas chromatography/mass spectrometry. This is the first time that the incorporation of 3-hydroxypivalic acid and therefore of a hydroxyalkanoic acid with two methyl group substituents at the α-carbon atom in a naturally occurring copolyester is reported. It indicates that 3-hydroxypivalic acid-coenzyme A is accepted by polyhydroxyalkanoic acid synthase as a substrate.     

Chromenes of polyketide origin from Peperomia villipetiola

An extract of leaves and stems of Peperomia villipetiola has been found to contain myristicin (3-methoxy-4,5-methylenedioxy-allylbenzene) and seven chromenes, whose structures are methyl 5-hydroxy-7-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (1), methyl 5-methoxy-7-methyl-2,2-dimethyl-2H-1-chromene-8-carboxylate (2), methyl 7-hydroxy-5-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (3), methyl 7-methoxy-5-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (4), 5-methanol-7-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylic acid (5), 5-methanol-7-methoxy-2,2-dimethyl-2H-1-chromene-6-carboxylic acid (6), and methyl 5-acetoxymethanol-7-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylate (7). A biosynthetic rationale for 1-7 suggests that orsellinic acid may be a common intermediate. The anti-fungal activities of the chromenes were measured bioautographically against Cladosporium cladosporioides and Cladosporium sphaerospermum: compounds 6 and 7 were found to be the most active.     

A chromene and prenylated benzoic acid from Piper aduncum.

In addition to nerolidol, 2',6'-dihydroxy-4'-methoxydihydrochalcone, methyl 2,2-dimethyl-8-(3'-methyl-2'-butenyl)-2H-1-chromene-6-carboxylate, methyl 2,2-dimethyl-2H-1-chromene-6-carboxylate and methyl 8-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylate, two new natural products were isolated from the leaves of Piper aduncum, 2,2-dimethyl-2H-1-chromene-6-carboxylic acid and 3-(3',7'-dimethyl-2',6'-octadienyl)-4-methoxybenzoic acid. The structures of the isolates were established based on analysis of spectroscopic data, including ES-MS. The DNA-damaging activity of the isolated compounds was also investigated against mutant strains of Saccharomyces cerevisiae.     

A facile one-pot synthesis of 4,5-diaryl-2,2-dimethyl-3(2H)-furanones

An efficient and practical one-pot synthesis of 4,5-diaryl-2,2-dimethyl-3(2H)-furanones has been achieved from 1,2-diarylethanones and 2-bromoisobutyryl cyanide in the presence of excess base, by employing the 'hard soft acid base' principle. The reaction scope of 2-bromoisobutyryl cyanide could be expanded to prepare a variety of 2,2-dimethyl-3(2H)-furanone derivatives other than 4,5-diaryl-2,2-dimethyl-3(2H)-furanones.     

Synthesis of 2,2-Dimethyl-3-Isopropylcyclopropyl Propionate

2,2-Dimethyl-3-isopropylcyclopropyl propionate, which Jacobson claimed to have synthesized in 1963 as the dihydro-derivative of the sex attractant of cockroach, was re-examined. The oxidation of ethyl 2,2-dimethyl-3-isopropylcyclopropyl ketone by using trifluoroperacetic acid as oxidant afforded the desired ester.     

Synthesis of the protected 6-16 segment of zervamicin 11-2, an application of the azirine/oxazolone method.

The protected 11 amino acid segment (6-16) of the peptaibol zervamicin II-2 was synthesized by using the 'azirine/oxazolone method' for the introduction of all Aib residues. Whereas a 2,2-dimethyl-2H-azirin-3-amine was used as the building block for Aib(7), methyl 2,2-dimethyl-2H-azirine-3-prolinate and -3-(3-hydroxyprolinate) proved to be ideally suited as dipeptide synthons for the introduction of Aib-Pro and Aib-Hyp, respectively. The coupling of Z-protected amino acids or peptide acids with the 2H-azirin-3-amines were performed in 75% to quantitative yield.     

Effect of sulfonates on the esterase activity of carboxypeptidase A

The effects of sulfonates on the carboxypeptidase A catalyzed hydrolysis of the ester substrate benzoylglycyl-L-phenyllactate were determined. The modifiers examined were benzenesulfonate, p-toluenesulfonate, 2-phenylethane-sulfonate, methanesulfonate, ethanesulfonate, propanesulfonate, butanesulfonate, pentanesulfonate, hexanesulfonate, heptanesulfonate, and 2,2-dimethyl-2-silapentane-5-sulfonate. Sulfonate activators of peptide hydrolysis were inhibitors of esterase activity. Of the sulfonates studied, 2,2-dimethyl-2-silapentane-5-sulfonate was the most effective inhibitor. 2-Phenylethanesulfonate, hexanesulfonate, heptanesulfonate, and 2,2-dimethyl-2-silapentane-5-sulfonate exhibited uncompetitive inhibition. The remaining sulfonates either did not inhibit or the inhibition was too weak to properly characterize.     

New phenolic inhibitors of the peroxidse-catalysed oxidation of indole-3-acetic acid

Previously we reported two metabolites of the insecticide carbofuran as persistent inhibitors of the peroxidase-catalysed oxidtion ofindole-3-acetic acid. In searching for more active inhibitors of this type, we have found that 5-hydroxy-2,2-dimethylchromene (β-tubanol), 2′,6′-dihydroxycetophenone oxime, 5-hydroxy-2,2-dimethylchroman, 2′,6′-dihydroxyacetophenone and 2,6-dihydroxybenzoic acid methyl ester were more active than the carbofuran metabolite 7-hydroxy-2,2-dimethyl-3-oxo-2,3-dihydrobenzofuran. Resorcinol, 5-hydroxy-2,2-dimethylchroman-4-one, 3-hydroxy-5-methoxy-2,2-dimethylchroman-4-one and 5-hydroxy-2-methylchrom-4-one were also inhibitory but with less activity. The new inhibitors differed from the well-known phenolic inhibitors such as caffeic acid in inhibition kinetics as demonstrated by the rate of disappearance of indole-3-acetic acid, the rate of formation of the oxidation products, and the transient spectral change in the enzyme.     

Selective synthesis of 3-hydroxy acids from Meldrum's acids using SmI2-H2O

The single-step synthesis of 3-hydroxy carboxylic acids from readily available Meldrum's acids involves a selective monoreduction using a SmI(2)-H(2)O complex to give products in high crude purity, and it represents a considerable advancement over other methods for the synthesis of 3-hydroxy acids. The protocol includes a detailed guide to the preparation of a single electron-reducing SmI(2)-H(2)O complex and describes two representative examples of the methodology: monoreduction of a fully saturated Meldrum's acid (5-(4-bromobenzyl)-2,2-dimethyl-1,3-dioxane-4,6-dione) and tandem conjugate reduction-selective monoreduction of α,β-unsaturated Meldrum's acid (5-(4-methoxybenzylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione). The protocol for selective monoreduction of Meldrum's acids takes ～6 h to complete.     

An electron spin resonance study of free radical intermediates in the oxidation of indole acetic acid by horseradish peroxidase

The oxidation of indole-3-acetic acid by horseradish peroxidase was studied using the spin traps t-nitrosobutane and 5,5-dimethyl-1-pyrroline N-oxide to trap free radical intermediates. The major free radical metabolite of indole acetic acid was unambiguously determined by the use of indole-3-[2,2-2H2]acetic acid to be the skatole carbon-centered free radical. In the presence of oxygen, superoxide was also trapped.     

Two naphthopyran derivatives from Faramea cyanea

Four anthraquinones and two new products, faramol (3,4-dihydro-3-hydroxy-2,2-dimethyl-2H-naphtho[1,2-b]pyran) and 7-methoxyfaramol (3,4-dihydro-3-hydroxy-7-methoxy-2,2-dimethyl-2H-naphtho[l,2-b]pyran), have been isolated from Faramea cyanea.     

Lead detoxification activities and ADMET hepatotoxicities of a class of novel 5-(1-carbonyl-L-amino-acid)-2,2-dimethyl-[1,3]dithiolane-4-carboxylic acids

By linking the mercapto groups with isopropyl and introducing l-amino acid into the 5-carboxyl of DMSA a class of novel 5-(1-carbonyl-l-amino-acid)-2,2- dimethyl-[1,3]dithiolane-4-carboxylic acids were prepared. Their in vivo activities were evaluated on lead loaded mice at the dose of 0.4 mmol/kg. The results showed that the lead levels of the livers, kidneys, femurs and brains in particular could be efficiently decreased by 0.4 mmol/kg of 5-(1-carbonyl-l-amino-acid)-2,2-dimethyl-[1,3]dithiolane-4-carboxylic acids. The benefit of 5-(1-carbonyl-l-amino-acid)-2,2-dimethyl-[1,3]dithiolane-4-carboxylic acids to the detoxification of the brain lead was attributed to their transmembrane ability. Compared with the lead detoxification efficacy, they did not affect the essential metals such as Fe, Cu, Zn, and Ca of the treated mice. Silico molecular modeling predicted that 5-(1-carbonyl-l-amino-acid)-2,2-dimethyl-[1,3]dithiolane-4-carboxylic acids had no hepatotoxicity.     

2,2-Dimethyl-1,3-propanediol as protective group promotes microbial hydroxylation of cis-bicyclo[3.3.0]octane-3,7-dione

Screening of several filamentous fungi for hydroxylation of cis-bicyclo[3.3.0]octane-3,7-dione showed only reduction of the keto groups. Several ways to protect the keto groups have been tested. This resulted in hydrolysis with subsequent reduction, or rejection of the substrate. Only when 2,2-dimethyl-1,3-propanediol was used to form diketals, the substrate was relatively stable and at least one hydroxylated product could be detected. © Rapid Science Ltd. 1998     

Organochalcogen compounds from glycerol: Synthesis of new antioxidants

We describe here a simple method for the synthesis of glycerol derivatives containing an organochalcogen unit (Se, Te and S) using NaBH₄ and PEG-400 as a solvent. The new methodology was used to synthesize a range of new organochalcogen compounds in good yields. Furthermore, four of synthesized compounds were evaluated for their antioxidant activity using different assays, such as 2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, nitric oxide (NO) and hydroxyl radical (OH) scavenging, ferric ion reducing antioxidant power (FRAP), ferrous ion chelating, superoxide dismutase-like activity and inhibition of linoleic acid lipid peroxidation. The new organotellurium 2,2-dimethyl-4-(phenyltellanylmethyl)-1,3-dioxolane 3j showed antioxidant activity and was more effective in inhibition of induced lipid peroxidation compared to solketal 4. Selenium and sulfur analogs 3a and 3m and solketal 4 did not present antioxidant effect. These findings suggest that 2,2-dimethyl-4-(phenyltellanylmethyl)-1,3-dioxolane 3j is a promising antioxidant and that its activity is influenced by the presence of the tellurium atom on the structure.     

Induction of carbofuran oxidation to 4-hydroxycarbofuran by Pseudomonas sp. 50432

Pseudomonas sp. 50432 biotransformed a highly toxic pesticide, carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) to 7-phenol (2,3-dihydro-2,2-dimethyl-7-hydroxy benzofuran) and several unknown metabolites. One of the unknown metabolites identified by gas chromatography/mass spectroscopy was 4-hydroxycarbofuran (2,3-dihydro-2,2-dimethyl-4-hydroxybenzofuran-7-yl methylcarbamate). It had a mass (237) similar to 3-hydroxycarbofuran and 5-hydroxycarbofuran but different fragmentation patterns. This is the first report in which an inducible oxidative enzyme, hydroxylase, mediated the conversion of carbofuran to 4-hydroxycarbofuran. A second constitutively synthesized enzyme hyrolase transformed carbofuran to 7-phenol.     

Novel retinoic acid 4-hydroxylase (CYP26) inhibitors based on a 3-(1H-imidazol- and triazol-1-yl)-2,2-dimethyl-3-(4-(phenylamino)phenyl)propyl scaffold

Retinoic acid (RA), the biologically active metabolite of vitamin A, is used medicinally for the treatment of hyperproliferative diseases including dermatological conditions and cancer. The antiproliferative effects of RA have been well documented as well as the limitations owing to toxicity and the development of resistance to RA therapy. RA metabolism inhibitors (RAMBAs or CYP26 inhibitors) are attracting increasing interest as an alternative method for enhancing endogenous levels of retinoic acid in the treatment of hyperproliferative disease. Here the synthesis and inhibitory activity of novel 3-(1H-imidazol- and triazol-1-yl)-2,2-dimethyl-3-(4-(phenylamino)phenyl)propyl derivatives in a MCF-7 CYP26A1 microsomal assay are described. The most promising inhibitor methyl 2,2-dimethyl-3-(4-(phenylamino)phenyl)-3-(1H-1,2,4-triazol-1-yl)propanoate (6) exhibited an IC(50) of 13 nM (compared with standards Liarozole IC(50) 540 nM and R116010 IC(50) 10 nM) and was further evaluated for CYP selectivity using a panel of CYP with >100-fold selectivity for CYP26 compared with CYP1A2, 2C9 and 2D6 observed and 15-fold selectivity compared with CYP3A4. The results demonstrate the potential for further development of these potent inhibitors.     

Deuterium isotope effect on enantioselectivity in the Comamonas testosteroni quinohemoprotein alcohol dehydrogenase-catalyzed kinetic resolution of rac-2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane,solketal

Isotopic substitution provides an effective tool to probe the mechanism of enzyme-catalyzed reactions. To our knowledge, kinetic isotope effects on the enantioselectivity of enzymes have not been reported. We investigated the effect of deuterium substitution on the enantiomeric ratio, E, of PQQ-containing quinohemoprotein alcohol dehydrogenase, QH-ADH, from Comamonas testosteroni in the ferricyanide-coupled kinetic resolution of rac-2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane, solketal. Under otherwise identical conditions, we measured E=30 for solketal and E=6 for rac-2,2-dimethyl-4-[1,1-2H]hydroxymethyl-1,3-[5,5,4-2H]dioxolane, d(5)-solketal. It is proposed that isotopic substitution affects the relative kinetic weights of the initial hydron/deuteron transfer from substrate to cofactor and the subsequent proton/deuteron shift in the cofactor-product complex. The latter step becomes more important in the deuterated complex to the extent that the enantiomer discrimination in the first step is partially overruled.     

Benzophenones of Garcinia pseudoguttifera (Clusiaceae)

Four biogenetically related benzophenones have been isolated from the Fijian Garcinia pseudoguttifera. They are: 6-hydroxy-2,4-dimethoxy-3,5-bis(3-methyl-2-butenyl)benzophenone (myrtiaphenone-A); 2,2-dimethyl-8-benzoyl-7-hydroxy-5-methoxy-6-(3-methyl-2-butenyl)benzopy ran (myrtiaphenone-B); 2,6-dihydroxy-4-methoxy-3,5-bis(3-methyl-2-butenyl)benzophenone (vismiaphenone-C) and a new benzophenone, 2,2-dimethyl-8-benzoyl-3,7-dihydroxy-5-methoxy- 6-(3-methyl-2-butenyl)-3,4-dihydrobenzopyran (pseudoguttiaphenone-A). Pseudoguttiaphenone-A could be biogenetically derived from vismiaphenone-C. The major component of G. pseudoguttifera was identified as eupha-8,24-dien-3 beta-ol.     

Evaluation of phenolic compounds in Brazilian propolis from different geographic regions

Chemometrics has been shown quite efficient to uncover relationships between chemical composition of a sample and its geographical origin. Forty propolis samples originated from the the South and South East of Brazil were analyzed by HPLC and 18 compounds of interest were studied which included: caffeic, p-coumaric and ferulic acids, and some of their derivatives, pinobanksin, a derivative of kaempferol and five phenolic compounds (assigned as 3-prenyl4-hydroxycinnamic acid (PHCA); 2,2-dimethyl-6-carboxyethnyl-2H-1-benzopyran (DCBE); 3,5-diprenyl-4-hydroxycinnamic acid (DHCA); compound E (still unknown) and 6-propenoic-2,2-dimethyl-8-prenyl-2H-1-benzopyran acid (DPB). Principal Component Analysis (PCA) indicated three different groups of propolis samples, having the same typical chromatogram, evaluated by HPLC. Samples from the South East group were rich in derivatives of kaempferol. Samples from the South group I had a high content of DPB compound, but a low concentration of kaempferol derivatives and of DCBEN compound. Samples from the South group II were characterized by a high concentration of DCBEN, DHCA, p-coumaric and DPB compounds. Therefore, the identification of new compounds in Brazilian propolis can give, useful information about the plant sources of a given geographic region.     

Studies on Chrysanthemic Acid

Pyrethrin II, cinerin II, allethrin II, pyrethrin II isomer, and allethrin II isomer were prepared by esterification of rethrolons with (+)-trans-pyrethric acid and (+)-trans-methyl-2,2-dimethyl-3-(2′-carboxy-l′-propenyl) cyclopropanecarboxylate and their relative toxicities to pyrethrin I, cinerin I and allethrin I against houseflies were measured by counting “mortality” and “knock-down percent”