Bioconversion of aminophosphonates to hydroxyphosphonatesviatwo step redox reactions employing fungi

(S)-Thienyl and (R)-Pirydyl phosphonate Derivatives Synthesized by Stereoselective Resolution of Their Racemic Mixtures With Rhodotorula mucilaginosa (DSM 70403) - Scaling Approaches

Rhodotorula mucilaginosa was successfully applied as a biocatalyst for the enantioselective resolution of the racemic mixtures of heteroatom phosphonates derivatives, resulting in receiving the following enantiomers: (S)-1-amino-1(2-thienyl)methylphosphonic acid (Product 1) and (R)-1-amino-1-(3'pirydyl) methylphosphonic acid (Product 2). Biological synthesis of both products is reported for the first time. Pure (S)-1-amino-1-(2-thienyl)methylphosphonic acid (Product 1) was isolated with a conversion degree of 50% after 24 h of biotransformation was conducted on a laboratory scale under moderate conditions (1.55 mM of substrate 1, 100 mL of distilled water, 135 rpm, 25°C; Method A). The scale was enlarged to semi-preparative one, using a simplified flow-reactor (Method C; 3.10 mM of substrate 1) and immobilized biocatalyst. The product was isolated with a conversion degree of 50% just after 4 h of biotransformation. Amino-1-(3'pirydyl)methylphosphonic acid (Substrate 2) was converted according to novel procedure, by the immobilized biocatalyst - Rhodotorula mucilaginosa. The process was carried out under moderate conditions (3.19 mM - substrate 2 solution; Method C1) with the application of a simplified flow reactor system, packed with the yeasts biomass entrapped in 4% agar-agar solution. Pure (R)-amino-1-(3'pirydyl)methylphosphonic (50% of conversion degree) was received within only 48 h.

First biological conversion of chiral heterophosphonate derivative - Scaling and paths of conversion discussion

Presented work describes the first approach for the biocatalytic resolution of racemic mixtures of heterophosphonate derivative. Penicillium funiculosum and Rhodotorula mucilaginosa were successfully applied for the biological conversion of racemic mixture of 1-amino-1-(3'-pyridyl)methylphosphonic acid 3. Both microorganisms carried out the kinetically driven process leading to conversion of one from the substrate enantiomers, leaving the second one unreacted. Application of R. mucilaginosa allowed obtaining pure enantiomer of the substrate (yield 100%, e.e 100% - unreacted isomer) after 24 h of biotransformation of 3 in the laboratory scale process (Method E), applying biocatalyst pre-treatment step - 24 h of starvation. In case of other biocatalyst, application of whole cells of P. funiculosum in laboratory scale process, also resulted in conversion of the racemic mixture of substrate 3via oxidative deamination into ketone derivative, which was then bioreduced (second step of the process) into 1-hydroxy-1-(3'-pyridyl)methylphosphonic acid 4. This time two products were isolated: unreacted substrate and hydroxy compound 4. Conversion degree ranged from 30% (standard procedure, method A) to even 70% (with extra addition of sodium pyruvate - method B2). However, in this case, bioconversion was not enantioselective - products: amino- and hydroxyderivative were obtained as racemic mixtures. Both biocatalysts were also tested towards the scaling so other biocatalytic procedures were introduced - with immobilized fungal mycelium. In case of Rhodotorula mucilaginosa this approach failed (data not shown) but Penicillium funiculosum turned out to be active and also selective. Thus, application of this biocatalyst in the half-preparative scale, continuous-flow bioprocess (Method C2) resulted in the obtaining of pure S-3 (100% e.e.) isomer with the 100% of conversion degree, without any side products. Recorded NMR spectra allowed confirming the reaction progress and its selectivity and also postulating possible mechanism of conversion.