Monica Ioana Toşa

Optically active 1-(benzofuran-2-yl)ethanols and ethane-1,2-diols by enantiotopic selective bioreductions

Abstract Enantiotopic selective reduction of 1-(benzofuran-2-yl)ethanones 1a – d , 1-(benzofuran-2-yl)-2-hydroxyethanones 4a – c and 2-acetoxy-1-(benzofuran-2-yl)ethanones 3a – c was performed by bakers yeast for preparation of optically active (benzofuran-2-yl)carbinols [( S )- 5a – d , ( S )- 6a – c and ( R )- 6a – c , enantiomeric excess from 55 to 93% ee].

Candida antarctica lipase A in the dynamic resolution of novel furylbenzotiazol-based cyanohydrin acetates

A series of novel (R)-furylbenzotiazol-based cyanohydrin acetates were prepared in over 90% isolated yields from the corresponding furancarbaldehydes. The one-pot method combines a basic resin to produce hydrogen cyanide from acetone cyanohydrin, an equilibrium between the formation and decomposition of furylbenzotiazol-based cyanohydrins and the unique enantioselectivity of Candida antarctica lipase A, allowing the acylation of (R)-cyanohydrins in the presence of vinyl acetate in anhydrous acetonitrile.

Kinetic resolution of 1-(benzofuran-2-yl)ethanols by lipase-catalyzed enantiomer selective reactions

Abstract Kinetic resolution of racemic 1-(benzofuran-2-yl)ethanols rac - 1a – d was performed by lipase-catalyzed enantiomer selective acylation ( E ≫100) yielding (1 R )-1-acetoxy-1-(benzofuran-2-yl)ethanes ( R )- 2a – d and (1 S )-1-(benzofuran-2-yl)ethanols ( S )- 1a – d in highly enantiopure form. The degree of enantiomer selectivity for enzymatic alcoholysis/hydrolysis processes starting from racemic 1-acetoxy-1-(benzofuran-2-yl)ethane rac - 2 was also tested under various conditions including supercritical CO 2 medium. Racemization-free lipase-catalyzed ethanolysis of the (1 R )-1-acetoxy-1-(benzofuran-2-yl)ethanes ( R )- 2a – d yielded almost quantitatively the enantiopure (1 R )-1-(benzofuran-2-yl)ethanols ( R )- 1a – d .

Immobilization of Phenylalanine Ammonia‐Lyase on Single‐Walled Carbon Nanotubes for Stereoselective Biotransformations in Batch and Continuous‐Flow Modes

Carboxylated single‐walled carbon nanotubes (SwCNTCOOH) were used as a support for the covalent immobilization of phenylalanine ammonia‐lyase (PAL) from parsley by two different methods. The nanostructured biocatalysts (SwCNTCOOH‐PALI and SwCNTCOOH‐PALII) with low diffusional limitation were tested in the batch‐mode kinetic resolution of racemic 2‐amino‐3‐(thiophen‐2‐yl)propanoic acid (1) to yield a mixture of (R)‐1 and (E)‐3‐(thiophen‐2‐yl)acrylic acid (2) and in ammonia addition to 2 to yield enantiopure (S)‐1. SwCNTCOOH‐PALII was a stable biocatalyst (>90 % of the original activity remained after six cycles with 1 and after three cycles in 6 M NH3 with 2). The study of ammonia addition to 2 in a continuous‐flow microreactor filled with SwCNTCOOH‐PALII (2 M NH3, pH 10.0, 15 bar) between 30–80 °C indicated no significant loss of activity over 72 h up to 60 °C. SwCNTCOOH‐PALII in the continuous‐flow system at 30 °C was more productive (specific reaction rate, rflow=2.39 μmol min−1 g−1) than in the batch reaction (rbatch=1.34 μmol min−1 g−1).

Nanobioconjugates of Candida antarctica lipase B and single-walled carbon nanotubes in biodiesel production.

Carboxylated single-walled carbon nanotubes (SWCNTCOOH) were used as support for covalent immobilization of Candida antarctica lipase B (CaL-B) using linkers with different lengths. The obtained nanostructured biocatalysts with low diffusional limitation were tested in batch mode in the ethanolysis of the sunflower oil. SWCNTCOOH-CaL-B proved to be a highly efficient and stable biocatalyst in acetonitrile (83.4% conversion after 4h at 35°C, retaining >90% of original activity after 10 cycles).

Synthesis of optically active 3-substituted-10-alkyl-10H-phenothiazine-5-oxides by enantioselective biotransformations

Abstract A series of racemic 10-alkyl-3-formyl-10 H -phenothiazine-5-oxides (±)- 2a – h were subjected to biotransformation with bakers yeast resulting in optically active aldehydes (+)- 2a – h and alcohols (−)- 3a – h in moderate enantiomeric excess. The racemic 10-alkyl-3-hydroxymethyl-10 H -phenothiazine-5-oxides (±)- 3a – h and 3-acetoxymethyl-10-alkyl-10 H -phenothiazine-5-oxides (±)- 4a – h obtained from the racemic aldehydes (±)- 2a – h were also tested in enantioselective lipase-catalyzed acetylations and alcoholysis reactions. The highest enantiomeric purities were achieved by a Novozyme 435-catalyzed acetylation–ethanolysis sequence, leading to optically active alcohols (−)- 3a – h in 83–92% e.e. A novel NMR method using enantiopure dibenzoyl tartaric acid as chiral additive was developed for determination of the enantiomeric composition of the optically active products.

Baker's yeast mediated preparation of (10-alkyl-10H-phenothiazin-3-yl)methanols

Abstract A series of 10-alkyl-10H-phenothiazine-3-carbaldehydes (2a–h) were obtained by Vilsmeier–Haack formylation from the corresponding 10-alkyl-10H-phenothiazines (1a–h) and reduced to (10-alkyl-10H-phenothiazine-3-yl)methanols (3a–h) by two alternative methods. The baker’s yeast catalyzed reaction proved to be superior over the NaBH4 reduction and yielded the desired 3-hydroxymethylphenothiazines (3a–h) almost quantitatively.

Chemo-enzymatic preparation of hydroxymethyl ketones

A series of hydroxymethyl ketones 4a–g were obtained from the corresponding halogenomethyl ketones 2a–gvia their transformation into acetoxymethyl ketones 3a–g by 18-crown-6 catalysed substitution with NaOAc followed by Novozyme 435™ catalysed ethanolysis. This convenient chemo-enzymatic route provides a mild, heavy-metal-free alternative to the direct α-hydroxylations of methyl ketones 1a–g.

Formyl- and acetylindols: Vibrational spectroscopy of an expectably pharmacologically active compound family

In the present paper, indole and its seven derivatives were compared, namely 3-formylindole, 1-methyl-3-formylindole, 1-ethyl-3-formylindole, 3-acetylindole, 1-methyl-3-acetylindole, 1-ethyl-3-acetylindole and 1,3-diacetylindole. The substitution of indole in position 3 with aldehydes and with alkyl groups cause only minor changes in the molecular geometry, however, substantially larger alterations are found in the charge distribution and in the vibrational force constants. The appearance of the aldehyde groups increased the degree of association as it was observable on the shape of infrared NH stretching band and its shifts. The alkyl substitution shifts the aldehyde carbonyl stretch band frequencies to somewhat higher values. The effect of the second acetyl group in position 1 is not comparable with those of the 1-alkyl groups. The latter effect is observable in the molecular geometry, however, it is more pronounced in the changes of the net charge distribution, the vibrational force constants and the infrared spectra.

Chemoenzymatic One‐Pot Synthesis of both (R)‐ and (S)‐Aryl‐1,2‐ethanediols

Both enantiomers of various 1‐aryl‐1,2‐ethanediols have been prepared in a one‐pot method from the corresponding arylethanones through the combination of chemical and enzymatic reactions. A range of aryl groups, phenyl, 4‐chlorophenyl, benzo[b]thiophene‐3‐yl, and benzofuran‐2‐yl, were used. The highly enantiomerically enriched (R)‐ and (S)‐1‐aryl‐1,2‐ethanediols were obtained with excellent yields, calculated for the arylethanones.