ABSTRACT
Functionalizations of cycloadducts are important steps for the use of Diels-Alder reactions in the construction of complex cyclic or polycyclic molecules from relatively simple starting materials. In the present work, we studied the ability of Penicillium brasilianum to perform microbial transformations of racemic Diels-Alder endo-cycloadducts. Thus, Diels-Alder products, obtained from reacting cyclopentadiene or 2,3-dimethylbutadiene with alkylated para-benzoquinones, were transformed by the resting cells of P. brasilianum producing new functionalized polycyclic compounds. These biotransformations yielded novel products of oxidation and ring closure, reduction of the C=C or C=O in [Formula: see text]-unsaturated system, and allylic hydroxylations. The reduction products (conjugated double bond and carbonyl group) were also synthesized, and the enantioselectivity of both in vitro and in vivo processes was evaluated. In all cases, the microbiological transformations were enantioselective. In silico docking studies of the Diels-Alder cycloadducts with P. brasilianum oxidoreductase "old yellow enzymes" shed more light on these transformations.
Subject(s)
Cycloaddition Reaction , Penicillium/metabolism , Biotransformation , Catalysis , Cyclization , Hydrogen Bonding , Hydrolysis , Models, Molecular , Molecular Conformation , Molecular Structure , Oxidation-Reduction , Polycyclic Compounds/chemistry , Polycyclic Compounds/metabolism , Substrate SpecificityABSTRACT
A quantitative profile of cytochalasin D production by Xylaria arbuscula was followed by growing the fungus in rice, Czapek, Czapek enriched with yeast extract, wheat, and corn. This cytochalasin producer, X. arbuscula, was collected as an endophytic fungus from healthy tissues of Cupressus lusitanica (Cupressaceae). A new HPLC method was developed using a synthetic N-acetyl-L-phenylalanine ethyl ester as internal standard, which showed a good correlation coefficient (r2 = 0.9995). The results varied from 6.40 to 39.55 mg per 100 g of culture medium, with wheat being the best medium for cytochalasin D production. The level of any free amino acids in the medium, not necessarily phenylalanine, appeared to be an important factor to enhance cytochalasin D biosynthesis.
