- The preparation and isolation of chloramphenicol palmitate in toluene
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The development of a process for the preparation of the antibiotic chloramphenicol palmitate that did not use methylene chloride and that fit into the production plant with improved yields and product quality is described. Addition of DMF as a co-solvent allowed the use of toluene for the reaction and the isolation. The product distribution observed by competitive esterification at the primary and secondary hydroxyl groups of chloramphenicol was well modeled by simple expressions for parallel consecutive reactions and estimated a 1000-fold difference in the rate constants for the two sites. A small increase in the impurity levels found during production plant trials was traced to trans-esterification during the extended processing time required at the 1000-kg scale.
- Daugs, Edward D.
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Read Online
- Activation of enzyme nanogel in organic solvents by PEG-substrate joint imprinting
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A substrate or polyethyleneglycol (PEG) imprinted lipase nanogel displayed increased apparent activity in organic solvents by 2.5-4.7 folds, compared to native lipase. It enabled a one-step synthesis of chloramphenicol palmitate with a yield of ～99% and purity of ～99%, indicating that the imprinted lipase nanogel is an appealing catalyst in organic media. This journal is
- Wang, Rui,Zhang, Yifei,Ge, Jun,Liu, Zheng
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p. 40301 - 40304
(2015/01/09)
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- Substrate imprinted lipase nanogel for one-step synthesis of chloramphenicol palmitate
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Enzymatic catalysis with high enantio- and regio-selectivity, which is attractive for green synthesis of chemicals, often suffers from low activity in organic solvents utilized as reaction media. Here, we describe a 'substrate-imprinted' lipase nanogel that displays high activity in organic solvents. The first step was to encapsulate lipase into polyacrylamide nanogel by an aqueous in situ polymerization. Then the lipase nanogel was lyophilized in the presence of palmitic acid, a substrate of lipase, followed by extraction with petroleum ether to remove palmitic acid from the lyophilized lipase nanogel. The imprinting treatment increased the adsorption capacity of palmitic acid by 2.9-fold and the apparent activity by 2-fold in catalyzing the transesterification reaction between para-nitrophenyl palmitate and ethanol. The effects of solvent and temperature on the yield and selectivity of the enzymatic synthesis of chloramphenicol palmitate were examined, respectively. One-step synthesis of chloramphenicol palmitate with the imprinted lipase nanogel gave a yield of ～99% and a purity of ～99% within 12 hours at 20 °C, whereas the imprinted free lipase gave a yield below 60% in 20 hours. The high activity and selectivity make the substrate-imprinted enzyme nanogel an attractive catalyst for green synthesis of chemicals having complex structures.
- Wang, Rui,Zhang, Yifei,Huang, Jinhai,Lu, Diannan,Ge, Jun,Liu, Zheng
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supporting information
p. 1155 - 1158
(2013/06/27)
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- Enzymatic regioselective production of chloramphenicol esters
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An enzymatic study has been performed in the search for synthetic routes to produce chloramphenicol derivatives through regioselective processes using lipases. Complementary transesterification and hydrolytic reactions have been carried to synthesize chloramphenicol regioisomers. Reaction parameters, such as biocatalyst, solvent, acyl donor, and temperature have been optimised in order to obtain chloramphenicol esters with high yields through acylation processes. Scale-up of the enzymatic reactions (1 g-scale at 0.25 M) and catalyst recycling (up to 10 cycles) have been successfully achieved. Furthermore, monoacylated derivatives at the more hindered secondary position could also be obtained employing hydrolysis processes.
- Bizerra, Ayla M.C.,Montenegro, Tasso G.C.,Lemos, Telma L.G.,De Oliveira, Maria C.F.,De Mattos, Marcos C.,Lavandera, Iván,Gotor-Fernández, Vicente,De Gonzalo, Gonzalo,Gotor, Vicente
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p. 2858 - 2862
(2011/05/12)
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- Development of column-free alkoxycarbonyl, aryloxycarbonyl, and acyl transfer reagents
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Easy-to-handle alkoxycarbonyl, aryloxycarbonyl, and acyl transfer reagents, which contain 3-nitro-1,2,4-triazole (NT) as a leaving group, were developed. With these reagents (NT reagents), which are stable nonhygroscopic crystalline materials, the reactions can be accomplished in about 5 min, and product can be isolated without tedious column chromatographic purification.
- Shimizu, Mamoru,Sodeoka, Mikiko
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experimental part
p. 1301 - 1312
(2009/07/05)
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- Synthesis of Ester Derivatives of Chloramphenicol by Lipase-Catalyzed Transesterification in Organic Solvents
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Regioselective esterification of chloramphenicol (1) and its synthetic analogue thiamphenicol (2) has been achieved by the action of lipase in acetone and several methyl carboxylates.Aliphatic and aromatic esters of different sizes and natures have been introduced selectively on the primary hydroxyl group of these molecules by modification of the reaction conditions (e.g., temperature, solvent, and lipase source).
- Ottolina, Gianluca,Carrea, Giacomo,Riva, Sergio
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p. 2366 - 2369
(2007/10/02)
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