A parametric study on biphasic medium conditions for the enantioselective production of naproxen by <Emphasis Type="Italic">Candida rugosa</Emphasis> lipase

A parametric study to increase the enantioselectivity of Candida rugosa lipase (CRL) toward S-Naproxen production by the hydrolysis of racemic Naproxen methyl ester in an aqueous-organic biphasic batch system was carried out. Effects of organic solvent type, aqueous phase/organic solvent volume ratio, agitation rate, concentrations of the substrate and the enzyme, pH of the aqueous phase, and temperature on the en antiomeric excess for the product (ee_p), on the enantiomeric ratio (E) and on the conversion (x) were evaluated. Employing isooctane as the solvent resulted in higher ee_p, E, and x than those obtained in hexane, cyclohexane, and toluene. The higher the volume ratio of aqueous phase/organic solvent employed, the higher the conversion and enantioselectivity achieved. The increase in agitation rate increased the hydrolysis rate. Higher concentration of racemic Naproxen methyl ester than 10 mg/mL decreased both the conversion and enantioselectivity. The increase in crude CRL concentration resulted in enhancement of x, but the decrease of fee_p and E. Acidic pH led to higher conversion and enantioselectivity than the medium and alkaline pH values. A further increase in temperature to over 45°C decreased the conversion and enantioselectivity. The highest enantiomeric ratio achieved in the S-Naproxen production was E=171.1, with x=49.8% and ee_p=95.7%.     

Enantioselective sulfa-Michael addition reaction of methyl thioglycolate to chalcones derivatives with sterically encumbered quinine squaramide organocatalyst

Asymmetric organocatalytic sulfa-Michael reactions give access to enantiomerically enriched sulfur containing adducts that can be used as valuable chiral building blocks. A variety of chalcone derivatives were allowed to react with methyl thioglycolate under optimized conditions, in the presence of a bifunctional quinine derived sterically encumbered squaramide organocatalyst, giving rise to excellent stereoselectivities, up to 99%?ee. The designed catalyst system proved to be efficient even at gram scale and under milder reaction conditions.     

Hospital service levels during drug shortages: Stocking and transshipment policies for pharmaceutical inventory

Journal of Global Optimization - In this study, we consider a health network that faces uncertain supply disruptions in the form of regional, nationwide, or worldwide drug shortages. Each hospital...     

Synthesis and Spectroscopic Properties of S-,O-Substituted Naphthoquinone Dyes

New S-,O-substituted naphthoquinone compounds (3a, 4b, 6, 7c, 9d, 10, 12, 13c, 14d, 15) were synthesized via vinilic substitution. 2,3-Dichloro-1,4-naphthoquinone gave 3a and 4b with 4,4′-thiobisbenzenethiol, respectively. Compounds 6 and 7c were obtained from the reaction of 2,3-dichloro-1,4-naphthoquinone with cyclohexylmercaptane. The compounds 9d and 10 were prepared from the reaction of 2,3-dichloro-1,4-naphthoquinone with 6-mercapto-1-hexanol. Compounds 12, 13c, 14d, and 15 were synthesized from the reaction of 2,3-dichloro-1,4-naphthoquinone with 1,6-hexanedithiol. Their structures were characterized by micro analysis, FT-IR, ¹H NMR, ¹³C NMR, MS, UV-Vis, and fluorescence spectroscopy.     

Lucidin type anthraquinone glycosides from Putoria calabrica

Two new lucidin type anthraquinone glycosides, putorinoside A (1) and putorinoside B (2) were isolated from Putoria calabrica, in addition to two known anthraquinone glycosides, lucidin 3-O-beta-glucopyranoside (3) and lucidin 3-O-primeveroside (4). Based on spectroscopic data, putorinosides A and B were identified as 2-hydroxymethyl-1-methoxy-3,5,6-trihydroxyanthraquinone 3-O-beta-glucopyranoside and 2-hydroxymethyl-1-methoxy-3,6-dihydroxyanthraquinone 3-O-beta-glucopyranoside, respectively.