Biodegradation of ethyl t-butyl ether (ETBE), methyl t-butyl ether (MTBE) and t-amyl methyl ether (TAME) by Gordonia terrae

Gordonia terrae strain IFP 2001 was selected from activated sludge for its capacity to grow on ethyl t-butyl ether (ETBE) as sole carbon and energy source. ETBE was stoichiometrically degraded to t-butyl alcohol (TBA) and the activity was inducible. A constitutive strain, G. terrae IFP 2007, derived from strain IFP 2001, was also selected. Methyl t-butyl ether (MTBE) and t-amyl methyl ether (TAME) were not used as carbon and energy sources by the two strains, but cometabolic degradation of MTBE and TAME was demonstrated, to TBA and t-amyl alcohol (TAA) respectively, in the presence of a carbon source such as ethanol. No two-carbon compound was detected during growth on ETBE, but formate was produced during cometabolic degradation of MTBE or TAME. A monooxygenase was involved in the degradation of ethers, because no degradation of ETBE was observed under anaerobic conditions and the presence of a cytochrome P-450 was demonstrated in G. terrae IFP 2001 after induction by cultivation on ETBE.     

Regioselectivity of enzymatic modification of poly(methyl acrylate)

Enzymes are potentially useful catalysts for polymerization as well as modification of polymers. While lipases have been used previously for polymerization reactions, they have not been used for modification of polymers. In this report, lipases were used to determine regioselective modification of ester functions in a telomer of poly(methyl acrylate). The influence of chain length on the extent of transesterification of methyl acrylate telomers of DP(n) 6-50 was studied by examining the relationship between the extents of enzymic modification to other telomerization parameters. The regioselectivity was observed when the average DP(n) of telomers is in a range of 6-22. At a higher DP(n) (>22), however, the average number of reacting ester functions per telomer strongly deviated from the theoretically predicted value. This phenomenon was suspected as a result of steric hindrance caused by folding of longer telomer chains. To verify this hypothesis, acrylate telomers at a DP(n) ranging from 10 to 42 were synthesized using a shorter telogen, i.e., 2,2'-ethanedithiol. The transesterification of these telomers showed a deviation in a degree of conversion when DP(n) was greater than 10, possibly indicating the inhibition caused by steric hindrance. Therefore, regioselective modification of acrylic polymers, which is difficult to achieve by conventional chemical methods, may be accomplished enzymatically.     

Cyclization studies with (±)-10,11-oxidofarnesyl acetate,methyl farnesate,and methyl (±)-10,11-oxidofarnesate

As models for lanosterol biosynthesis and for more elaborate biogenetic-type total synthesis in the di- and triterpenoid series, the nonenzymic cyclization of methyl farnesate, methyl (±)-10,11-oxidofarnesate and (±)-10,11-oxidofarnesyl acetate was studied. In addition to the 10,11-halohydrin, N-bromosuccinimide/water was observed to convert methyl farnesate to bromobicycles 40 and 41. Acid-catalyzed cyclization of (±)-10,11-oxido farnesate and the corresponding 2,3-cis isomer produced inter alia 3-hydroxy octalins 20a and 21a. Similarly, methyl (±)-10,11-oxidofarnesate was transformed to inter alia the hydroxylated bicyclic esters 34 and 35. Mechanistic and other aspects of these reactions are taken up.     

Synthesis of methyl alpha-D-glucopyranosyl-(1-->4)-alpha-D-galactopyranoside and methyl alpha-D-xylo-hex-4-ulopyranosyl-(1-->4)-alpha-D-galactopyranoside

The syntheses of methyl alpha-D-glucopyranosyl-(1-->4)-alpha-D-galactopyranoside (1) and methyl alpha-D-xylo-hex-4-ulopyranosyl-(1-->4)-alpha-D-galactopyranoside (4) are reported. The keto-disaccharide 4 is of interest in our design, synthesis, and study of pectate lyase inhibitors. The key step in the syntheses was the high-yielding, stereospecific formation of methyl 4,6-O-benzylidene-2',3'-di-O-benzyl-alpha-D-glucopyranosyl-(1-->4)-2,3,6-tri-O-benzyl-alpha-D-galactopyranoside (15), which was accomplished by reacting 2,3-di-O-benzyl-4,6-O-benzylidene-D-glucopyranosyl trichloroacetimidate (10) with methyl 2,3,6-tri-O-benzyl-alpha-D-galactopyranoside (14) in the presence of a catalytic amount of tert-butyldimethylsilyl trifluoromethane sulfonate (TMSOTF). Compound 15 was either hydrogenolyzed to yield disaccharide 1 or treated with NaBH3CN-HCl in 1:1 tetrahydrofuran-ether to yield methyl 2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl-(1-->4)-2,3,6-tri-O-benzyl-alpha-D-galactopyranoside (2). The free 4'-OH of compound 2 was oxidized to a carbonyl group by a Swern oxidation, and the protecting groups were removed by hydrogenolysis to yield keto-disaccharide 4. These synthetic pathways were simple, yet high yielding.     

Bis(o-trifluoromethylphenyl)dithiophosphinic methyl ester

When bis(o-trifluoromethylphenyl)dithiophosphinic acid (1) is dissolved in methanol, crystals of bis(o-trifluoromethylphenyl)dithiophosphinic methyl ester (2) are formed. The structure of dithiophosphinic methyl ester (2) has been characterized via single-crystal X-ray diffraction and multinuclear NMR studies. Compound 2 is remarkable in that the dithiophosphinic (PS₂) core is preserved during this transformation. The transformation to 2 suggests that the o-trifluoromethylphenyl groups on phosphorus assist in retaining the PS₂ core, possibly by steric hindrance.     

Cometabolism of methyl tert-butyl ether (MTBE) with alkanes

The release of methyl tert-butyl ether (MTBE) to the environment, mainly from damaged gasoline underground storage tanks or distribution systems spills, has provoked extended groundwater pollution. Biological treatments are, in general, a good alternative for bioremediation of polluted sites; however, MTBE elimination from environment has constituted a challenge because of its chemical structure and physicochemical properties. The combination of a stable ether link and the branched moiety hinder biodegradation. Initial studies found MTBE to be highly recalcitrant but, in the last decade, reports of its biodegradation have been published first under aerobic conditions and just recently under anaerobic conditions. Microbial MTBE degradation is characterized by bacteria having low growth rates (0.35 day⁻¹) and biomass yields (average value 0.24 g biomass/g MTBE). Alternatively, cometabolism (defined as the transformation of a non-growth substrate in the obligate presence of a growth substrate), has been considered since it uncouples biodegradation of the contaminant from growth, reducing the long adaptation and propagation period. This period has been reported to be of several months in systems where it is degraded as sole carbon source. Cometabolic degradation rates are between 0.3 and 61 nmol/min/mg protein (in the same range of direct aerobic metabolism). However, a major concern in MTBE cometabolism is that the accumulation of tert-butyl alcohol (TBA) may, under certain cases, result in an incomplete site cleanup. This paper reviews in detail the implicated enzymes and field treatments for the cometabolism of MTBE degradation with alkanes as growth substrates.     

Molecular Mobility in Poly(butyl methacrylate) and Poly(methyl methacrylate)

Molecular mobility is studied in poly(butyl methacrylate) and poly(methyl methacrylate) (PMMA) with molecular dynamics simulations in order to understand the effect of the α–β crossover on the β relaxation activation energy and co-operativity. In the high frequency range investigated, the estimated β process activation energy is decreased as compared to the low frequency value. This deviation is stronger in poly(n butyl methacrylate) (PnBMA) than in PMMA. The intra-molecular co-operativity related to the β process is also higher in PnBMA than in PMMA. These results could be related to the relative position of the simulation temperature range and of the extrapolated α–β crossover temperature.     

Inheritance of triterpene methyl ethers in Cortaderia (Gramineae)

The distribution of triterpene methyl ethers in several generations of interspecific hybrids of Cortaderia indicates dominant gene control of their synthesis. The hybrid C. richardii × C. toetoe is an exception because synthesis of α- and β-amyrin methyl ethers is suppressed in F₁ and F₂, but is restored in the backcross F₁ × C. toetoe; this backcross generation was heterozygous for genes for the amyrin methyl ethers, and on selfing segregated in a simple Mendelian ratio.     

Triterpene methyl ethers of Chionochloa (Gramineae)

The leaf wax of twenty species of Chionochloa was examined for triterpene methyl ethers; twelve species gave positive yields. The known pentacyclic methyl ethers arundoin, miliacin, lupeol methyl ether and β-amyrin methyl ether were identified and the methyl ethers of the tetracyclic alcohols, cycloartenol and parkeol are reported as new natural products. Arundoin and miliacin occur in many species while the remaining compounds may be suitable chemotaxonomic markers.     

Functionalization of poly(methyl methacrylate) (PMMA) as a substrate for DNA microarrays

A chemical procedure was developed to functionalize poly(methyl methacrylate) (PMMA) substrates. PMMA is reacted with hexamethylene diamine to yield an aminated surface for immobilizing DNA in microarrays. The density of primary NH₂ groups was 0.29 nmol/cm². The availability of these primary amines was confirmed by the immobilization of DNA probes and hybridization with a complementary DNA strand. The hybridization signal and the hybridization efficiency of the chemically aminated PMMA slides were comparable to the hybridization signal and the hybridization efficiency obtained from differently chemically modified PMMA slides, silanized glass, commercial silylated glass and commercial plastic Euray™ slides. Immobilized and hybridized densities of 10 and 0.75 pmol/cm², respectively, were observed for microarrays on chemically aminated PMMA. The immobilized probes were heat stable since the hybridization performance of microarrays subjected to 20 PCR heat cycles was only reduced by 4%. In conclusion, this new strategy to modify PMMA provides a robust procedure to immobilize DNA, which is a very useful substrate for fabricating single use diagnostics devices with integrated functions, like sample preparation, treatment and detection using microfabrication and microelectronic techniques.     

Synthesis of bis-(methyl 3,4,6-tri-O-acetyl-D-glucopyranosid-2-yl)-oxamides

The synthesis of a new bis-(D-glucopyranosid-2-yl)oxamides via the key intermediate, N-acetyl N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl) oxamic acid chloride (2alpha) is described. Treatment of compound 2alpha with methyl 3,4,6-tri-O-acetyl-2-amino-2-deoxy-beta-D-glucopyranoside afforded N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl)-N'-(methyl 3,4,6-tri-O-acetyl-beta-D-glucopyranosid-2-yl)-oxamide. Reaction of 2alpha with 1,2-diaminoethane afforded 1,2-bis-[N,N'-(methyl 3',4',6'-tri-O-acetyl-alpha-D-glucopyranosid-2'-yl)]ethyloxamide as a main product, while 2-N-[N'-(methyl 3',4',6'-tri-O-acetyl-alpha-D-glucopyranosid-2'-yl)oxamide]-ethyl acetamide was formed as a side product. Reaction of 2alpha with 1,3-diamino-2-hydroxypropane gave only 1,3-bis-N,N-[N'-(methyl 3',4',6'-tri-O-acetyl-2'-deoxy-alpha-D-glucopyranosid-2'-yl)-oxamido]-2-propanol.     

Regioselective nitration of N(alpha),N(1)-bis(trifluoroacetyl)-L-tryptophan methyl ester: efficient synthesis of 2-nitro and 6-nitro-N-trifluoroacetyl-L-tryptophan methyl ester

Nitration of N(alpha),N(1)-bis(trifluoroacetyl)-l-tryptophan methyl ester with HNO(3) in acetic anhydride at 0 degrees C provides N(alpha)-trifluoroacetyl-2-nitro-l-tryptophan methyl ester in 67% yield, whereas nitration in trifluoroacetic acid at 0 degrees C gives N(alpha)-trifluoroacetyl-6-nitro-l-tryptophan methyl ester in 69% yield.