Joannes B.P.A. Wijnberg

Asymmetric reduction of ketones via whole cell bioconversions and transfer hydrogenation: complementary approaches

Abstract Prochiral aryl and dialkyl ketones were enantioselectively reduced to the corresponding alcohols using whole cells of the white-rot fungus Merulius tremellosus ono991 as a biocatalytic reduction system and ruthenium(II)–amino alcohol and iridium(I)–amino sulfide complexes as metal catalysts in asymmetric transfer hydrogenation. Comparison of the results showed that the corresponding chiral alcohols could be obtained with moderate to high enantioselectivities (e.e.s of up to 98%). The biocatalytic and transfer hydrogenation approaches appear to be complementary. The biocatalytic approach is the most suitable for the enantioselective reduction of chloro-substituted (aryl) ketones, whereas in the reduction of α,β-unsaturated compounds excellent results were obtained using the catalytic hydrogenation protocol.

The synthesis of mono- and dihydroxy aromadendrane sesquiterpenes, starting from natural (+)-aromadendrene-III

Abstract The monoalcohols (−)-globulol ( 2 ), (−)-epiglobulol ( 3 ), (−)-ledol ( 4 ), and (+)-viridiflorol ( 5 ) were synthesized from (+)-aromadendrene ( 1 ). The cis-fused alloaromandedrone ( 14 ), the key intermediate used in the synthesis of 4 and 5 , was obtained from the trans-fused apoaromadendrone ( 13 ) via a selective protonation of the thermodynamic enol trimethylsilylether 15 . After hydroxylation of the tertiary C11 of 13 with RuO 4 , (+)-spathulenol ( 6 ), (−)-allospathulenol ( 7 ), and the aromadendrane diols 8 – 11 could be prepared. Compounds 2 – 11 were tested for antifungal properties, but their activity was only moderate.

Elimination and detoxification of softwood extractives by white-rot fungi.

The ability of several white-rot fungal strains to remove and detoxify acetone extractives (pitch or resin) in Scots pine sapwood was investigated in stationary laboratory batch assays. Fungal pretreatment provided up to 62% total pitch reduction and significant decreases in pitch toxicity. The best strains were Bjerkandera sp. strain Stereum hirsutum and Trametes versicolor that eliminated over 93% of the problematic triglyceride fraction and 58-87% of other lipophilic extractive classes in only 2 weeks. Fungal removal of the wood extractives was accompanied by a 7.4-16.9-fold decrease in their inhibitory effect, as determined in the Microtox bioassay. Wood pretreatment by Bjerkandera sp. and T. versicolor caused limited losses of woody mass (less than 4% in 4 weeks); whereas S. hirsutum led to somewhat higher mass losses (7% in 4 weeks). These results indicate the potential of white rot fungi to control pitch deposition problems in pulping and to reduce the aquatic toxicity caused by naturally-occurring lipophilic extractives in forest industry effluents.

De-novo biosynthesis of chlorinated aromatics by the white-rot fungus Bjerkandera sp. BOS55 : formation of 3-chloro-anisaldehyde from glucose

The white‐rot fungus Bjerkandera sp. BOS55 produced de‐novo several aromatic metabolites. Besides veratryl alcohol and veratraldehyde, compounds which are known to be involved in the ligninolytic system of several other white‐rot fungi, other metabolites were formed. These included anisaldehyde, 3‐chloro‐anisaldehyde and a yet unknown compound containing two chlorine atoms. Additionally GC/MS analysis revealed the production of small amounts of anisyl alcohol and 3‐chloro‐anisyl alcohol. After 14 days, the extracellular fluid of Bjerkandera BOS55 contained 100 μM veratraldehyde and 50 μM 3‐chloro‐anisaldehyde. This is the first report of de‐novo biosynthesis of simple chlorinated aromatic compounds by a white‐rot fungus. Anisaldehyde and 3‐chloro‐anisaldehyde were also produced by Bjerkandera adusta but not by Phanerochaete chrysosporium.

Degradation and detoxification of softwood extractives by sapstain fungi.

Abstract Wood extractives (resin) cause pitch deposition problems and effluent toxicity in pulp and papermaking. The ability of six sapstaining fungi to degrade and detoxify extractive constituents in Scots pine sapwood was examined, and the results were compared with those obtained with the commercial depitching fungus Cartapip (Ophiostoma piliferum). Pestalotiopsis crassiuscula and O. piliferum were the best strains and they provided high reductions of total resin (50–60% in 6 weeks). Both strains were highly effective in the degradation of individual extractive components including triglycerides, diglycerides and free fatty acids. Although all strains displayed moderate to high pitch degradation, their detoxifying capacity was limited. Two important exceptions were Ceratocystis deltoideospora and O. piliferum that caused a 11–14-fold decrease in toxicity (Microtox bioassay). These results indicate the potential of wood pretreatment with the selected sapstain fungi for minimizing pitch problems and decreasing effluent toxicity in pulping.

The Synthesis of Germacrane Sesquiterpenes and Related Compounds

A review is presented of the various methods for the preparation of germacrane sesquiterpenes and related compounds.

Novel monochlorinated metabolites with a 1-benzoxepin skeleton from Mycena galopus

Two novel monochlorinated 2,3-dihydro-1-benzoxepin derivatives were isolated from the ethyl acetate extracts of the stipes of Mycena galopus. The structures were established on the basis of their spectral data.

Novel chlorometabolites produced by Bjerkandera species

The EtOAc extract from the extracellular fluid of the mycelium of Bjerkandera sp. BOS55 contained four novel chlorinated benzoic acid derivatives, i.e. 3-chloro-4-hydroxybenzoic acid, 3,5-dichloro-4-hydroxybenzoic acid, methyl 3,5-dichloro-4-hydroxybenzoate and methyl 3,5-dichloro-p-anisate. 3-Chloro-4-hydroxybenzoic acid was also produced by B. adusta.

The synthesis of (-)-kessane, starting from natural (+)-aromadendrene-II

Abstract Starting from the readily available chiral synthon 5 the sesquiterpene ether (−)-kessane (1) can be synthesized in a 9 steps reaction sequence in an overall yield of 43%.

Trichlorinated phenols from hypholoma elongatum

Three trichlorinated phenols, 2,4,6-trichloro-3-methoxyphenol, 3,5,6-trichloro-2,4-dimethoxyphenol and 3,4,6-trichloro-2,5-dimethoxyphenol, were detected as novel metabolites in the ethyl acetate extract from the culture medium of the Basidiomycete, Hypholoma elongatum (strain WIJS94-28).