Titanium carbenoid-mediated cyclopropanation of allylic alcohols: selectivity and mechanism.

A new method for the chemo- and stereoselective conversion of allylic alcohols into the corresponding cyclopropane derivatives has been developed. The cyclopropanation reaction was carried out with an unprecedented titanium carbenoid generated in situ from Nugent's reagent, manganese and methylene diiodide. The reaction involving the participation of an allylic hydroxyl group, proceeded with conservation of the alkene geometry and in a high diastereomeric excess. The scope, limitations and mechanism of this metal-catalysed reaction are discussed.

The synthesis of 3-hydroxy-2,4,8-trimethyldec-8-enolides and an approach to 3,4-dihydroxy-2,4,6,8-tetramethyldec-8-enolide.

The synthesis of several derivatives of 3-hydroxy-2,4,8-trimethyldec-8-enolide and attempts at the synthesis of 3,4-dihydroxy-2,4,6,8-tetramethyldec-8-enolide (1), a structure which has been assigned to a metabolite of the phytopathogenic fungus, Botrytis cinerea, gave products whose spectroscopic data had significant differences from those reported for the natural product 1. The rare 11-membered lactone rings were constructed by ring-closing metathesis reactions. The increase in conformational restrictions imposed by the substituents has a high influence on the stereochemistry of the ring-closing metathesis reaction and gives rise to a decrease in the yield for the synthesis of 11-membered lactones. The predominant alkene which was obtained was the (Z)-isomer. The observed spectroscopic differences between the synthesized lactones and the natural product and the spectroscopic data of its acetylated derivative 26a allowed us to revise the structure 1 to that of the γ-butyrolactone 26.

Exploring mutasynthesis to increase structural diversity in the synthesis of highly oxygenated polyketide lactones.

The enantioselective synthesis of (2R,3R,4E,8E)-3-hydroxy-2,4,8-trimethyldeca-4,8-dienolide (5) by ring-closing metathesis is described. This compound is an analogue of 3,4-dihydroxy-2,4,6,8-tetramethyldec-8-enolide (4) which is a rare 11-membered lactone produced by the fungus, Botrytis cinerea. Mutasynthetic studies with compound 5 using two mutants of B. cinerea led to the isolation of four new highly oxygenated 11-membered lactones (11-14) in which compound 5 has been stereoselectively epoxidized and hydroxylated at sites that were not easily accessible by classical synthetic chemistry.

Reflex control of posterior shoulder muscles from arm afferents in healthy people.

In order to position the hand during functional tasks, control of the shoulder is required. Heteronymous reflexes from the upper limb to shoulder muscles are used to assist in this control. To investigate this further, the radial and ulnar nerves were stimulated at elbow level whilst surface electromyographic activity of posterior deltoid, infraspinatus and latissimus dorsi muscles were recorded. In addition, the cutaneous branch of the radial nerve and the skin of the fifth digit were stimulated in order to investigate any cutaneous contribution to reflex activity. Reflexes were evoked in all three of these shoulder muscles from hand and/or forearm afferents. However, the reflexes differed; whereas both excitatory and inhibitory reflexes were evoked in posterior deltoid and infraspinatus, the reflexes in latissimus dorsi were mainly excitatory. Cutaneomuscular reflexes were seldom evoked here, but when they were present they were generally evoked at longer latencies than the reflexes evoked by mixed nerve stimulation. The results suggest a role for reflexes originating from the forearm and/or hand in the control of the shoulder.

An unusual case of facial nerve palsy following soccer related minor head injury.

A 16 year old amateur soccer player sustained a minor head injury while contesting a ball in the air. He was unconscious for two minutes and remained "dizzy" for about an hour. After two days he developed a profound left lower motor neurone facial nerve palsy. He was found to have a complex fracture of the left petrous temporal bone, with fluid in the left middle ear and left mastoid. Treatment was conservative with oral steroids and oral co-amoxiclav and a left myringotomy to decompress his middle ear. The spectrum of aetiology, presentation, and prognosis for facial nerve injuries is discussed.

Steroids: reactions and partial synthesis.

The article reviews the progress in the chemistry of the steroids that was published between January and December, 2000. The reactions and partial syntheses of estrogens, androgens, pregnanes, cholic acid derivatives, cholestanes and vitamin D analogues are covered. There are 169 references.

Novel rearrangements of sesquiterpenoid panasinsane derivatives under acidic conditions.

The sesquiterpenoid panasinsane derivatives 11 and 14-16 have been prepared from caryophyllene oxide (7). The novel rearrangement reactions of compounds 11 and 14 under TCNE-catalyzed solvolysis conditions and the reactions of compounds 15 and 16 under superacid conditions (HSO3F/Et2O, -63 degrees C) have been investigated. The ginsenol derivative 17 is obtained from compounds 11 and 14 under TCNE-catalyzed conditions. The rearrangement of compounds 15 and 16 under superacid conditions leads to the novel sesquiterpene derivatives (1S,4S,7S,10S,11S)-3,3,10,11-tetramethyltricyclo[5.3.1.0(4,10)]undecan-1,11-yl sulfate (19) and (1S,4S,5S,8S)-2,2,4,8-tetramethyl tricyclo[3.3.2.1(4,8)]undecan-11-one (20). The influence of the secondary hydroxyl group at C-5 of the panasinsane derivatives on the course of these rearrangements is discussed.

Substrate interactions in BTEX and MTBE mixtures by an MTBE-degrading isolate.

Groundwater contaminant plumes from recent accidental gasoline releases often contain the fuel oxygenate MTBE (methyl tert-butyl ether) together with BTEX (benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene) compounds. This study evaluates substrate interactions during the aerobic biotransformation of MTBE and BTEX mixtures by a pure culture, PM1, capable of utilizing MTBE for growth. PM1 was unable to degrade ethylbenzene and two of the xylene isomers at concentrations of 20 mg/L following culture growth on MTBE. In addition, the presence of 20 mg/L of ethylbenzene or the xylenes in mixtures with MTBE completely inhibited MTBE degradation. When MTBE-grown cells of PM1 were exposed to MTBE/benzene and MTBE/toluene mixtures, MTBE degradation proceeded, while the degradation of benzene and toluene was delayed for several hours. Following this initial lag, benzene and toluene were degraded rapidly, while the rate of MTBE degradation slowed significantly. MTBE degradation did not increase to previous rates until benzene and toluene were almost entirely degraded. The lag in benzene and toluene degradation was presumably due to the induction of the enzymes necessary for BTEX degradation. Once these enzymes were induced, sequential additions of benzene or toluene were degraded rapidly, and growth on benzene and toluene was observed. The results of this study suggest that BTEX and MTBE degradation occurs primarily via two independent and inducible pathways. If subsurface microbial communities behave similarly to the culture used in this study, the observed severe inhibition of MTBE degradation by ethylbenzene and the xylenes and the partial inhibition by benzene and toluene suggest thatthe biodegradation of MTBE in subsurface environments would most likely be delayed until MTBE has migrated beyond the BTEX plume.

Isolate PM1 populations are dominant and novel methyl tert-butyl ether-degrading bacterial in compost biofilter enrichments.

The gasoline additive MTBE, methyl tert-butyl ether, is a widespread and persistent groundwater contaminant. MTBE undergoes rapid mineralization as the sole carbon and energy source of bacterial strain PM1, isolated from an enrichment culture of compost biofilter material. In this report, we describe the results of microbial community DNA profiling to assess the relative dominance of isolate PM1 and other bacterial strains cultured from the compost enrichment. Three polymerase chain reaction (PCR)-based profiling approaches were evaluated: denaturing gradient gel electrophoresis (DGGE) analysis of 230 bp 16S rDNA fragments; thermal gradient gel electrophoresis (TGGE) analysis of 575 bp 16S rDNA fragments; and non-denaturing polyacrylamide gel electrophoresis of 300-1,500 bp fragments containing 16S/23S ribosomal intergenic transcribed spacer (ITS) regions. Whereas all three DNA profiling approaches indicated that PM1-like bands predominated in mixtures from MTBE-grown enrichments, ITS profiling provided the most abundant and specific sequence data to confirm strain PM1's presence in the enrichment. Moreover, ITS profiling did not produce non-specific PCR products that were observed with T/DGGE. A further advantage of ITS community profiling over other methods requiring restriction digestion (e.g. terminal restriction fragment length polymorphisms) was that it did not require an additional digestion step or the use of automated sequencing equipment. ITS bands, excised from similar locations in profiles of the enrichment and PM1 pure culture, were 99.9% identical across 750 16S rDNA positions and 100% identical across 691 spacer positions. BLAST comparisons of nearly full-length 16S rDNA sequences showed 96% similarity between isolate PM1 and representatives of at least four different genera in the Leptothrix subgroup of the beta-Proteobacteria (Aquabacterium, Leptothrix, Rubrivivax and Ideonella). Maximum likelihood and parsimony analyses of 1,249 nucleotide positions supported isolate PM1's position in a separate lineage within the Leptothrix subgroup.

Linking toluene degradation with specific microbial populations in soil.

Phospholipid fatty acid (PLFA) analysis of a soil microbial community was coupled with (13)C isotope tracer analysis to measure the community's response to addition of 35 microg of [(13)C]toluene ml of soil solution(-1). After 119 h of incubation with toluene, 96% of the incorporated (13)C was detected in only 16 of the total 59 PLFAs (27%) extracted from the soil. Of the total (13)C-enriched PLFAs, 85% were identical to the PLFAs contained in a toluene-metabolizing bacterium isolated from the same soil. In contrast, the majority of the soil PLFAs (91%) became labeled when the same soil was incubated with [(13)C]glucose. Our study showed that coupling (13)C tracer analysis with PLFA analysis is an effective technique for distinguishing a specific microbial population involved in metabolism of a labeled substrate in complex environments such as soil.

Biodegradation of methyl tert-butyl ether by a bacterial pure culture.

A bacterial strain, PM1, which is able to utilize methyl tert-butyl ether (MTBE) as its sole carbon and energy source, was isolated from a mixed microbial consortium in a compost biofilter capable of degrading MTBE. Initial linear rates of MTBE degradation by 2 x 10(6) cells ml(-1) were 0.07, 1.17, and 3.56 microg ml(-1) h(-1) for initial concentrations of 5, 50, and 500 microg MTBE ml(-1), respectively. When incubated with 20 microg of uniformly labeled [(14)C]MTBE ml(-1), strain PM1 converted 46% to (14)CO(2) and 19% to (14)C-labeled cells within 120 h. This yield is consistent with the measurement of protein accumulation at different MTBE concentrations from which was estimated a biomass yield of 0.18 mg of cells mg MTBE(-1). Strain PM1 was inoculated into sediment core material collected from a contaminated groundwater plume at Port Hueneme, California, in which there was no evidence of MTBE degradation. Strain PM1 readily degraded 20 microg of MTBE ml(-1) added to the core material. The rate of MTBE removal increased with additional inputs of 20 microg of MTBE ml(-1). These results suggest that PM1 has potential for use in the remediation of MTBE-contaminated environments.

The microbiological hydroxylation of 3 alpha,5-cycloandrostanes by Cephalosporium aphidicola.

The microbiological hydroxylation of some 3 alpha,5-cycloandrostanes by the fungus, Cephalosporium aphidicola has been shown to take place at C-2 alpha and C-14 alpha and a 6 beta-alcohol was oxidized to the 6-ketone.

Oxidation of Two Pregnane Steroids Catalyzed by the Fungus Cephalosporium aphidicola.

Two pregnane steroids, pregnane (1) and 3ß-hydroxypregnane (2), were oxidized by fermentation with the fungus Cephalosporium aphidicola. The fermentation of pregnane (1) yielded 3ß-hydroxypregnane (2) and 3ß, 6ß,11α-trihydroxypregnane (3), while that of 3ß-hydroxypregnane (2) afforded 6ß,11α-dihydroxypregn-3,20-dione (4), 3ß,6ß,15α-trihydroxypregn-20-one (5) and 3ß,5α,11α-trihydroxypregn-20-one (6). The metabolites are characterized by detailed physical and spectroscopic studies.