Rosanna Cardillo

Structures of melleolides B-D, three antibacterial sesquiterpenoids from Armillaria mellea

Abstract The structures of melleolides B-D, three new protoilludene sesquiterpenoid O-methylorsellinates isolated from a culture of Armillaria mellea , have been elucidated on the basis of chemical and spectral data.

Trifluoromethyl vs. methyl ability to direct enantioselection in microbial reduction of carbonyl substrates.

Abstract The stereoselective reduction of 3-trifluoromethylcyclohexanone ( 1a ), ( E )-1,1,1-trifluoro-4-phenyl-3-buten-2-one ( 3a ), and their unfluorinated analogues 1b and 3b has been performed with some growing microorganisms. Differences in the electronic and steric properties of the trifluoromethyl and methyl residues result in different chemo- and stereoselectivities in the microbial reduction of phenylbutenones 3a and 3b while cyclohexanones 1a and 1b showed strictly similar stereoselectivities. A new protocol based on 13 C NMR spectra of 2-phenylpropionic acid esters has been used to assign the absolute configuration of the obtained secondary alcohols.

Secondary mould metabolites. Part 47. Isolation and structure elucidation of clavilactones A–C, new metabolites from the fungus Clitocybe clavipes

Clavilactones A–C (1, 4 and 5) have been isolated from cultures of the Basidiomycetous fungus Clitocybe clavipes. Their structures and relative configurations have been deduced from 1H and 13C NMR studies, chemical reactions and single-crystal X-ray analysis of the dimethyl ether derivative 3. 1H–1H coupling constants, NOE data and molecular modelling calculations all suggest that the molecules have little conformational mobility and the conformation adopted in solution by clavilactone A 1 and dimethyl ether derivative 3 is essentially identical with that of 3 in the solid state. Clavilactones A–C exhibit antifungal and antibacterial activity and inhibit the growth germination of Lepidium sativum. A possible biogenetic origin of clavilactone A 1 is discussed.

The biosynthesis of aureothin

Abstract Feeding experiments with specifically labelled precursors show that the nitroaromatic, C-6-C-1 unit of the antibiotic aureothin (9) biologically derives by degradation of the C-6-C-3, phenylpropanoid precursor D,L -p-aminophenylalanine (1) through hydroxylation β to the nitrogen to erythro and threo p-aminophenylserine (3 and 4). During the biosynthesis there is the loss of the hydrogen originally present in benzylic position in the phenylpropanoid precursor, and, further, the oxidation of the p-amino group to p-nitro takes place very late in the sequence.

Two cinnamic allenic ethers from the fungus Clitocybe eucalyptorum

Abstract The structure of eucalyptene A, a fungal metabolite isolated from Clitocybe eucalyptorum , has been determined to be 4′-(2″,3″-butadienyloxy) trans -cinnamic acid methyl ester on the basis of 1 H and 13 C NMR evidence and chemical synthesis. Minor amounts of its cis isomer, eucalyptene B, were also isolated.

Microbial reduction of α,α,α-trifluoro-α′-sulfenylketones

Abstract Several microorganisms have been employed in the reduction of two α,α,α-trifluoro-α′-sulfenylketones. Some of them produce corresponding alcohols in high diastero- and enantioselection, the high conversion in a single enantiomer being secured by the racemization of starting ketones in the biotransformation conditions. Transformation of obtained sulfenyl-trifluoromethyl-alcohols into trifluoromethyl-epoxides is also described.

On the steric course of the microbial generation of (Z6)-gamma-dodecenolactone from (10R, S) 10-hydroxy-octadeca-(E8, Z12)-dienoic acid

Summary(Z6)-gamma-dodecenolactone samples produced endogenously inFusariumpoae and biogenerated from (10R, S) 10-hydroxy-octadeca-(E8, Z12)-dienoic acid inCladosporiumsuaveolens show (R) and (S) configurations, respectively.

Formation of the (R)- and (S)-enantiomers of ethyl 3-hydroxybutanoate and of 1-(1,3-dithian-2-yl)-2-hydroxypropane by microbial reduction

The (R)and (S) enantiomers of 3-hydroxybutanoate [(2a) or (3a)] and 1-(1,3-dithian-2-yl)-2-hydroxypropane [(2b) or (3b)] are obtained from ethyl 3-oxobutanoate (1a) and 1-(1,3-dithian-2-yl)-2-oxopropane (1b), respectively, using growing cultures from different strains of Geotrichum candidum and Aspergillus niger.

Enantioselective reduction of racemic abscisic acid by Aspergillus niger cultures

Biotransformation of racemic abscisic acid [(±)-ABA]1a with cultures of Aspergillus niger gives rise to the enantioselective reduction of the (S)-enantiomer to afford the corresponding (1′S, 2′R)-(–)-2′,3′-dihydro-ABA acid 2a in high enantiomeric excess (e.e.). The structure, stereochemistry, and preferred conformation of compound 2a have been elucidated on the basis of NMR evidence.

Secondary mould metabolites. Part 19. Structure elucidation and absolute configuration of melledonals B and C, novel antibacterial sesquiterpenoids from Armillaria mellea. X-Ray molecular structure of melledonal C

The structure, absolute configuration, and preferred conformation, both in the solid state and in solution, of melledonal C (11), a Δ2,3-protoilludene sesquiterpenoid from Armillaria mellea, have been established by a combination of X-ray and n.m.r. procedures. Ring A of the protoilludene skeleton was found in the crystal in a slightly twisted envelope conformation with C(10) displaced 0.55 A below the C(9), C(13), C(12), C(11) plane; ring B is a (7β,9α) flattened half-chair and ring C assumes a (4β,6β) highly puckered conformation. A strong intramolecular hydrogen bond between the 4-OH proton and the oxygen atom of 10-OH was evidenced in the solid state as well as in solution ([2H6]acetone) using the SIMPLE 1H n.m.r. method (secondary isotope multiplet n.m.r. of partially labelled entities). Contrary to what is observed in solution, in the solid state there is no hydrogen bonding between the 3′-OH proton and the oxygen atom of the adjacent CO2R group. The structure of melledonals A (9) and B (10), and the absolute configuration at C(13) of melleolides C (6) and D (7) have also been elucidated by n.m.r. and chemical evidence.