The solubility of artemisnin in 12 different organic solvents, methanol, ethanol, butanol, acetone, ethyl acetate, isopropyl acetate, acetonitrile, hexane, heptane, 2-butanone (MEK), methyl tert-butyl ether (MTBE), and toluene, as well as in three binary solvent mixtures of ethyl acetate + ethanol, ethyl acetate + acetone, and ethanol + acetone, within the temperature range of (284.10 and 323.15) K, is obtained. The solubility data were fitted to the Two-Liquid-Non-Random (NRTL) activity coefficient equation to obtain the model binary interaction parameters, which were used to predict the solubility of artemisinin in ethyl acetate and acetone or ethanol binary solvent mixtures. The predicted values compared favorably with the experimental data.
The asymmetric enzymatic ketone reduction of 4,4-dimethoxytetrahydro-2H-pyran-3-one provided the (R)-r-hydroxyketal, an important chiral precursor for a pharmaceutical intermediate, with high enantioselectivity (>99% ee). An economical process including in situ NADPH-cofactor regeneration using glucose dehydrogenase has been developed to produce the desired material in high yield (96-98%). The two-enzyme process was employed at pilotplant scale to produce 80 kg of (R)-4,4-dimethoxytetrahydro-2Hpyran-3-ol. Critical factors for scale-up were found to be pH control and agitation speed.
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