- Synthesis of 4-sulfur-substituted (2S,3R)-3-phenylserines by enzymatic resolution. Enantionure precursors for thiamphenicol and florfenicol
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Enantiomerically pure 4-methylthio- and 4-methylsulfonylsubstitutcd (2S,3R)-3-phenylserines are prepared by enzymatic resolution of the corresponding racemic threo amides using the amidase from Ochrobactrum anthropi NCIMB 40321. The unwanted (2R,3S) enantiomers of the amides are separated from the enantiopure amino acids and easily racemized after Schiff base formation with the corresponding 4-(methylthio)- and 4-(methylsulfonyl)benzaldehyde. The racemization can be combined with the preparation of the racemic amides by aldol reaction under crystallization conditions to yield only the threo isomers. Enantiopure (25,3R)-3-[4-(methylthio)phenyl]serine and (2S,3R)-3-[4-(methylsulfonyl)phenyl]serine are thus obtained in 78% and 62% overall yields starting from the corresponding substituted benzaldehydes. (2S,3A)-3-[4-(Methylthio)phenyl]serine is reduced to (1R,2R)-2-amino-1-[4-(methylthio)phenyl]propane-1,3-diol with NaBH4/H2SO4 and can be used for the synthesis of thiamphenicol and florfenicol.
- Kaptein, Bernard,Van Dooren, Thei J.G.M.,Boesten, Wilhelmus H. J.,Sonke, Theo,Duchateau, Alexander L.L.,Broxterman, Quirinus B.,Kamphuis, Johan
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- Phenylserine amides and the preparation of phenylserines/phenylserine amides
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Process for the preparation of a threo-phenylserine amide of the general formula 2 in which glycine amide is contacted with the corresponding substituted benzaldehyde of formula 3 in an excess relative to the amount of glycine amide, this taking place at a pH between 9 and 14 in the presence of a suitable solvent. The resulting phenylserine amide can subsequently be hydrolyzed to a phenylserine amide of the general formula 1, which is subsequently hydrolyzed to a phenylserine amide of the general formula 1, which is subsequently subjected to a stereoselective enzymatic hydrolysis yielding a (2S,3R) phenylserine. The non-hydrolyzed (2R,3S) phenylserine amide can be isolated as a Schiff base and be recirculated and simply racemized. The (2S,3R) phenylserine obtained can be used in the preparation of thiamphenicol or florfenicol. The threo-phenylserine amides of the general formula 1 or 2 are new intermediates in this commercially attractive process for the preparation of thiamphenicol and florfenicol.
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- Asymmetric synthesis using sulfinimines (thiooxime S-oxides)
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The addition of diethylaluminum cyanide and the lithium enolate of methyl α-bromoacetate to sulfinimines (thiooxime S-oxides) is highly diastereoselective affording α-amino nitriles and N-sulfinylaziridines, respectively. Hydrolysis of the α-amino nitriles gives α-amino acids in high ee, while hydrolysis of N-sulfinylaziridine carboxylic acids give β-hydroxy-α-amino acids. The latter compounds were transformed into (+)-thiamphenicol, a broad spectrum antibiotic and sphingosine, an important component of the sphingolipids.
- Davis, Franklin A.,Portonovo, Padma S.,Reddy, Rajarathnam E.,Reddy, G. Venkat,Zhou, Ping
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p. 291 - 303
(2007/10/03)
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- Asymmetric synthesis of the antibiotic (+)-thiamphenicol using cis-N-(p-toluenesulfinyl)aziridine 2-carboxylic acids
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A concise, highly efficient asymmetric synthesis of aminopropanediol (1R,2R)-(-)-3, precursor to the broad spectrum antibiotics thiamphenicol/florfenicol 1/2, was prepared in two steps from cis-aziridine 2-carboxylic acid (2S,3S)-(-)-5.
- Davis, Franklin A.,Zhou, Ping
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p. 7525 - 7528
(2007/10/02)
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- Process for the stereochemical inversion of (2S,3S)-2-amino-3-phenyl-1,3-propanediols into their (2R,3R) enantiomers
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A four step process for transforming (2S,3S)-2-amino-3-phenyl-1,3-propanediols into their (2R,3R)-enantiomers is described. The final compounds are useful intermediates for the synthesis of antibiotics like Chloramphenicol, Thiamphenicol and Florfenicol. The starting products generally are discard products in the synthesis of said antibiotics.
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- Process for the preparation of trans-(5R)-2,4,5-trisubstituted 2-oxazolines
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A process for the preparation of 2,4,5-trisubstituted 2-oxazoline compounds having trans-(5R) configuration from precursors wherein the carbon atom that will be at position 5 in the oxazoline ring, has S configuration, is described.
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- Direct Conversion of (1S,2S)-2-Amino-1--1,3-propanediol into Its Enantiomer for Efficient Synthesis of Thiamphenicol and Florfenicol
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The usual synthesis of thiamphenicol and florfenicol involves the resolution of racemic threo-2-amino-1--1,3-propanediol into its 1S,2S and 1R,2R isomers ((+)-3 and (-)-3), of which only the latter is a useful precursor.An efficient conversion of the 1S,2S isomer into the 1R,2R enantiomer in high yield, is described.
- Giordano, Claudio,Cavicchioli, Silvia,Levi, Silvio,Villa, Marco
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p. 6114 - 6118
(2007/10/02)
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- Process for the stereochemical inversion of (2S,3S)-2-amino-3-phenyl-1,3-propanediols into their (2R,3R) enantiomers
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A four step process for transforming (2S,3S)-2-amino-3-phenyl-1,3--propanediols into their (2R,3R)-enantiomers is described. The final compounds are useful intermediates for the synthesis of antibiotics like Chloramphenicol, Thiamphenicol and Florfenicol. The starting products generally are discard products in the syn-thesis of said antibiotics.
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- An enzymatic route to florfenicol
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Racemic ethyl threo-3-14-methylthiophenyl)serinate is resolved by enzymatic hydrolysis using protease from Streptomyces griseus and both stereoisomers are converted to D-threo-4,5-dihydro-5-(4-methylsulfonylphenyl)-2-phenyl-4-oxazolemethan ol, thereby giving a formal synthesis of florfenicol.
- Clark,Fischer,Schumacher
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p. 891 - 894
(2007/10/02)
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- Reversed-phase liquid chromatographic separation of enantiomeric and diastereomeric bases related to chloramphenicol and thiamphenicol.
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The important antimicrobial agents chloramphenicol and thiamphenicol are N-acylated amines whose chemical structures include two chiral centers. Each drug is the single enantiomer of R,R configuration. The N-deacylated bases of the drugs are important intermediates in their synthesis and optical resolution. In this report, reversed-phase HPLC methods are described for the separation of enantiomeric and diastereomeric bases of the two drugs and of two closely related bases used in some syntheses of the drugs. The stereoisomeric bases were derivatized with a homochiral isothiocyanate and the resulting diastereomeric thioureas were separated on C18 columns with methanol:water mixtures as mobile phases and detection at 254 nm. The four stereoisomeric bases of chloramphenicol and those of its unnitrated analogue were thus separable after derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate. This reagent also allowed the separation of the D-threo isomer of the p-mercaptomethyl analogue of thiamphenicol base from its stereoisomers. The stereoisomers of thiamphenicol base were similarly separated with (R)-alpha-methylbenzyl isothiocyanate as the derivatizing agent. The diastereomers of chloramphenicol base and of thiamphenicol base were chromatographically separable after derivatization with the nonchiral reagent benzyl isothiocyanate. The procedures developed may be useful in the determination of the stereoisomeric composition of the drugs in research and in quality control, and may be applicable to other similar agents whose chemistry and pharmacology are receiving considerable attention.
- Gal,Meyer-Lehnert
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p. 1062 - 1065
(2007/10/02)
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- NEW STRATEGY FOR RACEMIZATION OF 2-AMINO-1,3-PROPANEDIOLS, KEY INTERMEDIATES FOR THE SYNTHESIS OF ANTIBIOTIC DRUGS
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A new strategy for racemization of the 2-amino-1,3-propanediol 2b, based on a chemoselective oxazoline ring formation and a highly diastereoselective reduction of the ketone 4 is reported.
- Giordano, Claudio,Cavicchioli, Silvia,Levi, Silvio,Villa, Marco
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p. 5561 - 5564
(2007/10/02)
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- MILD RECOVERY OF β-AMINO ALCOHOLS FROM THE CORRESPONDING 2-OXAZOLIDINONES
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A mild ring cleavage of N-tert-butoxycarbonyl-2-oxazolidinones (N-BOC-2-oxazolidinones) 5a-5d and the recovery of β-amino alcohols 7a-7d from the corresponding N-BOC-derivatives are reported.
- Jommi, Giancarlo,Ripa, Alberto,Ripa, Giorgio,Sisti, Massimo
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