Yngve Stenstrøm

Cleavage of cellulose by a CBM33 protein

Bacterial proteins categorized as family 33 carbohydrate‐binding modules (CBM33) were recently shown to cleave crystalline chitin, using a mechanism that involves hydrolysis and oxidation. We show here that some members of the CBM33 family cleave crystalline cellulose as demonstrated by chromatographic and mass spectrometric analyses of soluble products released from Avicel or filter paper on incubation with CelS2, a CBM33‐containing protein from Streptomyces coelicolor A3(2). These enzymes act synergistically with cellulases and may thus become important tools for efficient conversion of lignocellulosic biomass. Fungal proteins classified as glycoside hydrolase family 61 that are known to act synergistically with cellulases are likely to use a similar mechanism.

Efficient separation of oxidized cello-oligosaccharides generated by cellulose degrading lytic polysaccharide monooxygenases

We present an evaluation of HPLC-based analytical tools for the simultaneous analysis of native and oxidized cello-oligosaccharides, which are products of enzymatic cellulose degradation. Whereas cello-oligosaccharides arise from cellulose depolymerization by glycoside hydrolases, oxidized cello-oligosaccharides are produced by cellobiose dehydrogenase and the recently identified copper dependent lytic polysaccharide monooxygenases (LPMOs) currently classified as CBM33 and GH61. The latter enzymes are wide-spread and expected to play crucial roles in further development of efficient enzyme technology for biomass conversion. Three HPLC approaches with well documented performance in the field of oligosaccharide analysis have been investigated: high-performance anion-exchange chromatography (HPAEC), hydrophilic interaction chromatography (HILIC) and porous graphitized carbon liquid chromatography (PGC-LC). HPAEC with pulsed amperometric detection (PAD) was superior for analysis of oxidized oligosaccharides, combining the best separation with superior sensitivity for oligosaccharide species with a degree of polymerization (DP) ranging from 1 to 10. Furthermore, the HPAEC method can be optimized for operation in a high-throughput manner (run time 10 min). Both PGC-LC and HILIC allow reasonable run times (41 and 25 min, respectively), with acceptable separation, but suffer from poor sensitivity compared to HPAEC-PAD. On the other hand, PGC-LC and HILIC benefit from being fully compatible with online mass spectrometry. Using an LC-MS setup, these methods will deliver much better sensitivity than what can be obtained with conventional detectors such as ultraviolet-, charged aerosol-, or evaporative light scattering and may reach sensitivities similar to or even better than what is obtained in HPAEC-PAD. Pure oxidized cello-oligosaccharide standards, ranging from DP2 to DP5, were obtained by semi-preparative PGC and characterized by MS and NMR analysis.

First total synthesis of (−)-aplyolide A

Abstract The first total synthesis of (−)-aplyolide A † , (16 S )-methyloxacyclohexadeca-(5 Z ,8 Z ,11 Z ,14 Z )-tetraen-2-one, 1 is reported. The synthesis is based on three consecutive couplings of terminal alkynes with propargylic halides and proves the absolute configuration of the stereogenic center of the natural product.

A Facile Formal Synthesis of Volicitin

Abstract A short and concise synthesis of volicitin is presented. The synthesis is based on repeated chemoselective copper salt cross coupling reactions of alkynes and propargylic halides.

Direct biocatalytic synthesis of functionalizedcatechols: a green alternative to traditional methods with high effectivemass yield

Several catechols have been prepared directly from aromatic precursors by treatment with the recombinant organism Escherichia coli JM109 (pDTG602), which expresses both toluene dioxygenase (TDO) and dihydrocatechol dehydrogenase (DHCD), the first two enzymes in the natural biodegradation pathway of aromatics by Pseudomonas species. The yields and the ease of preparation of these compounds are compared with traditional chemical methods. For three of the products, the E value and EMY (effective mass yield, is defined as the percentage of the mass of desired product relative to the mass of all non-benign materials in its synthesis, see ref. 9) are calculated and compared with those obtained by traditional methods to indicate the green component of the preparation. Potential for direct introduction of the catechol unit to various natural product synthons is discussed.

Direct biooxidation of arenes to corresponding catechols with E. coli JM109 (pDTG602). Application to synthesis of combretastatins A-1 and B-1

Convergent syntheses of combretastatins A-1 and B-1 were accomplished via coupling of biocatalytically generated p-bromomethoxycatechol with trimethoxyphenylacetylene.

Base catalysed isomerisation of aldoses of the arabino and lyxo series in the presence of aluminate

Base-catalysed isomerisation of aldoses of the arabino and lyxo series in aluminate solution has been investigated. L-Arabinose and D-galactose give L-erythro-2-pentulose (L-ribulose) and D-lyxo-2-hexulose (D-tagatose), respectively, in good yields, whereas lower reactivity is observed for 6-deoxy-D-galactose (D-fucose). From D-lyxose, D-mannose and 6-deoxy-L-mannose (L-rhamnose) are obtained mixtures of ketoses and C-2 epimeric aldoses. Small amounts of the 3-epimers of the ketoses were also formed. 6-Deoxy-L-arabino-2-hexulose (6-deoxy-L-fructose) and 6-deoxy-L-glucose (L-quinovose) were formed in low yields from 6-deoxy-L-mannose and isolated as their O-isopropylidene derivatives. Explanations of the differences in reactivity and course of the reaction have been suggested on the basis of steric effects.

Synthetic efforts towards the protoilludenes. A formal synthesis of Δ7-protoilludene

Abstract An improved route to 5,8,8-trimethylbicyclo[4.3.0]-4-nonen-3-one, a key intermediate for the synthesis of the protoilludane skeleton and in particular Δ7-protoilludene, is reported. Attempts on an alternative synthesis of Δ6-protoilludene based on a phenylsulfonyl allene cycloaddition reaction is also presented.

Synthesis of (+) lineatin, an aggregation pheromone component oftrypodendrom Lineatum

Abstract An efficient six-step synthesis of racemic lineatin ( 1 ) is described. The key reaction is a thermal intramolecular ene-allen cyclization.

Atmospheric Fate of Nitramines: An Experimental and Theoretical Study of the OH Reactions with CH3NHNO2 and (CH3)2NNO2

The rates of CH3NHNO2 and (CH3)2NNO2 reaction with OH radicals were determined relative to CH3OCH3 and CH3OH at 298 ± 2 K and 1013 ± 10 hPa in purified air by long path FTIR spectroscopy, and the rate coefficients were determined to be k(OH+CH3NHNO2) = (9.5 ± 1.9) × 10(-13) and k(OH+(CH3)2NNO2) = (3.5 ± 0.7) × 10(-12) (2σ) cm(3) molecule(-1) s(-1). Ozone was found to react very slowly with the two nitramines, k(O3+nitramine) < 10(-21) cm(3) molecule(-1) s(-1). Product formation in the photo-oxidation of CH3NHNO2 and (CH3)2NNO2 was studied by FTIR, PTR-ToF-MS, and quantum chemistry calculations; the major products in the OH-initiated degradation are the corresponding imines, CH2═NH and CH3N═CH2, and N-nitro amides, CHONHNO2 and CHON(CH3)NO2. Atmospheric degradation mechanisms are presented.