Kinetic resolution of trans-2-(1-pyrazolyl)cyclohexan-1-ol catalyzed by lipase B from Candida antarctica

Spectroscopic Evidence for Intramolecular MoVI(O2)····HO−C Hydrogen Bonding in Solution

“…The absolute configuration of the non-acylated derivative was determined by X-ray-crystallographic methods (see below). For the corresponding 2-pyrazolylcyclohexanol, an identical stereoselectivitiy of the enzymatic esterification was found [10] . Figure 1 shows the molecular structure of (1S,2S)-1 in the solid state, along with characteristic bond lengths and angles.…”

“…Heating a 1:1.5 mixture of 2-[3(5)-pyrazolyl]pyridine and epoxycyclohexane for 4 h at 170°C in a pressure tube [7] gives rac-trans-2- [3-(2-pyridyl of water per formula unit. In the solid state structure of enantiomerically pure 2-pyrazolylcyclohexanol [10] , the molecules are linked by hydrogen bonds between the hydroxy groups and the pyrazole moieties, resulting in a helical arrangement. In the case of (1S,2S)-1, this kind of molecular organization is hampered by the bulky pyridyl ring.…”

“…However, we expect the cyclohexane ring to occupy the thermodynamically favored chair conformation with both substituents oriented in an equatorial position, as found in similar compounds [8] . Since we are interested in such compounds as enantiomerically pure ligands for enantioselective catalysis and as starting material for the synthesis of chiral ligands [9] , we investigated the kinetic resolution of 1 [10] . Acylation of 1 with isopropenyl acetate in the presence of lipase B from candida antarctica [11] selectively leads to the formation of the acetate with the (1R,2R) configuration (Scheme 1), which can be separated from (1S,2S)-1 by preparative MPLC.…”

On the way to chiral epoxidations with methyltrioxorhenium(VII) derived catalysts

“…We therefore synthesized some chiral pyrazole derivatives, which are now more easily accessible particularly due to the work of Brunner and co-workers [28][29][30][31]. With a catalyst to substrate ratio of 1:100 and reaction temperatures of À30°C enantiomeric excess up to 27% are obtained in the epoxidation of cis-methyl styrene.…”

Asymmetric synthesis of azolium-based 1,2,3,4-tetrahydronaphthalen-2-ols through lipase-catalyzed resolutions

“…8 Also, recently racemic cycloalkyl azoles have been described as potent antileishmanial agents. 9 In this context, lipase-catalyzed resolutions of pyrazole-, 10 imidazole-11 and triazolecycloalkanols 12 have been studied in depth in the last two decades. The application of this class of hydrolytic enzymes provides an efficient access to alcohol and ester derivatives with high stereodiscrimination.…”