Chemoenzymatic enantioselective and stereo-convergent syntheses of lisofylline enantiomers via lipase-catalyzed kinetic resolution and optical inversion approach

Chemoenzymatic deracemization of lisofylline catalyzed by a (laccase/TEMPO)-alcohol dehydrogenase system

“…Optical rotations ([α]) were measured with a PolAAr 32 polarimeter in a 2 dm long cuvette using the sodium D line (λ = 589 nm). 1 H NMR (500 MHz) and 13 C NMR (126 MHz) spectra were recorded on a Varian NMR System 500 MHz spectrometer. The 1 H and 13 C chemical shifts (δ) are reported in parts per million (ppm) relative to the solvent signals [CDCl 3 , δ H (residual CHCl 3 ) 7.26 ppm, δ C 77.16 ppm].…”

“…1 H NMR (500 MHz) and 13 C NMR (126 MHz) spectra were recorded on a Varian NMR System 500 MHz spectrometer. The 1 H and 13 C chemical shifts (δ) are reported in parts per million (ppm) relative to the solvent signals [CDCl 3 , δ H (residual CHCl 3 ) 7.26 ppm, δ C 77.16 ppm]. Chemical shifts are presented as s (singlet), d (doublet), dd (doublet of doublets), t (triplet), q (quartet), m (multiplet), and br s (broad singlet); coupling constants (J) are reported in hertz.…”

“…Mp 108-111 °C (Et 2 O) [lit. 43 104-106 °C (CHCl 3 )]; R f [CHCl 3 /acetone (90 : 10, v/v)] 0.15; 1 H NMR (500 MHz, CDCl 3 ): δ 1.58-1.70 (m, 4H), 2.12 (s, 3H), 2.48 (t, J = 7.1 Hz, 2H), 3.55 (s, 3H), 3.96 (s, 3H), 3.99 (t, J = 7.1 Hz, 2H), 7.49 (s, 1H); 13 General procedure for the synthesis of silylated lisofylline rac-3. To a solution of racemic lisofylline (rac-1, 118 mg, 0.42 mmol) in CH 2 Cl 2 (3 mL), N,Obis(trimethylsilyl)acetamide (BSA, 342 mg, 1.68 mmol, 415 μL) was added in one portion, and the reaction mixture was stirred at 40 °C for 30 min.…”

“…Next, the volatile compounds were evaporated under vacuum, and the crude product was purified by SiO 2 column chromatography using a mixture of CHCl 3 /MeOH (95 : 5, v/v) as an eluent to afford the desired silylated lisofylline rac-3 (102 mg, 0.30 mmol, 69%) as a white solid. 1.72 (m, 3H), 3.56 (s, 3H), 3.71-3.79 (m, 1H), 3.97 (d, J = 0.5 Hz, 3H), 3.99 (s, 2H), 7.48 (d, J = 0.5 Hz, 1H); 13 In an open-to-air test tube, TEMPO (4.1 mg, 33 mol%) was added to a suspension of racemic lisofylline (rac-1, 23 mg, 0.08 mmol, 50 mM final conc.) in a monophasic mixture of oxygen-saturated 50 mM citrate buffer (pH 5)/organic solvent (10-50% (v/v)), for a total volume of 1.6 mL.…”

“…Alternative enzymatic approaches relying on the microbial bioreduction of PTX using cell cultures of Rhodotorula rubra DSM 5436 exhibiting Prelog stereoselectivity 10 or chemo- and stereoselective hydroxylation of 1- N -hexyl-theobromine catalyzed by wild-type 11 or engineered human cytochrome P450 3A4 monooxygenases 12 seem to be less attractive from the viewpoint of undesired absolute configuration or low enantiomeric excess values of the obtained non-racemic LSF, respectively. With the aim to expand the synthetic toolbox for the synthesis of the titled API, we have recently developed two independent variants of lipase-catalyzed kinetic resolution (KR) of racemic LSF by either using a classic transesterification approach with vinyl acetate as acyl donor 13 or utilizing α-angelica lactone as a nonconventional irreversible acylating agent for chromatography-free KR. 14 However, enzymatic KR of sec -alcohols suffers from low reaction yields, which renders the use of this approach unsustainable for industrial applications.…”