Efficient preparation of enantiomerically pure α-aryl-α-trifluoromethylglycines via Auto Seeded Programmed Polythermic Preferential Crystallization of 5-aryl-5-trifluoromethylhydantoins
摘要:
Both pure enantiomers of alpha-phenyl- (or alpha-(p-methoxyphenyl))-alpha-trifluoromethyl-glycine and their corresponding methyl esters were obtained on a preparative scale using the following four-step sequence: the preparation of 5-aryl-5-trifluoromethylhydantoins by a Bucherer-Bergs reaction starting from trifluoromethyl aryl ketones, optical resolution by Auto Seeded Programmed Polythermic Preferential Crystallization (AS3PC), basic hydrolysis of the enantiopure hydantoins by means of aqueous barium hydroxide, and esterification of the amino acids with trimethylsilyldiazomethane. Hydantoins 5 and 6 were proven to crystallize as conglomerates using first second harmonic generation and then X-ray powder diffraction. The absolute stereochemistry of (+)-5-phenyl-5-trifluoromethylhydantoin 5b was established to be (S) by X-ray diffraction analysis on a single-crystal. (C) 2010 Elsevier Ltd. All rights reserved.
Efficient preparation of enantiomerically pure α-aryl-α-trifluoromethylglycines via Auto Seeded Programmed Polythermic Preferential Crystallization of 5-aryl-5-trifluoromethylhydantoins
摘要:
Both pure enantiomers of alpha-phenyl- (or alpha-(p-methoxyphenyl))-alpha-trifluoromethyl-glycine and their corresponding methyl esters were obtained on a preparative scale using the following four-step sequence: the preparation of 5-aryl-5-trifluoromethylhydantoins by a Bucherer-Bergs reaction starting from trifluoromethyl aryl ketones, optical resolution by Auto Seeded Programmed Polythermic Preferential Crystallization (AS3PC), basic hydrolysis of the enantiopure hydantoins by means of aqueous barium hydroxide, and esterification of the amino acids with trimethylsilyldiazomethane. Hydantoins 5 and 6 were proven to crystallize as conglomerates using first second harmonic generation and then X-ray powder diffraction. The absolute stereochemistry of (+)-5-phenyl-5-trifluoromethylhydantoin 5b was established to be (S) by X-ray diffraction analysis on a single-crystal. (C) 2010 Elsevier Ltd. All rights reserved.
Efficient preparation of enantiomerically pure α-aryl-α-trifluoromethylglycines via Auto Seeded Programmed Polythermic Preferential Crystallization of 5-aryl-5-trifluoromethylhydantoins
Both pure enantiomers of alpha-phenyl- (or alpha-(p-methoxyphenyl))-alpha-trifluoromethyl-glycine and their corresponding methyl esters were obtained on a preparative scale using the following four-step sequence: the preparation of 5-aryl-5-trifluoromethylhydantoins by a Bucherer-Bergs reaction starting from trifluoromethyl aryl ketones, optical resolution by Auto Seeded Programmed Polythermic Preferential Crystallization (AS3PC), basic hydrolysis of the enantiopure hydantoins by means of aqueous barium hydroxide, and esterification of the amino acids with trimethylsilyldiazomethane. Hydantoins 5 and 6 were proven to crystallize as conglomerates using first second harmonic generation and then X-ray powder diffraction. The absolute stereochemistry of (+)-5-phenyl-5-trifluoromethylhydantoin 5b was established to be (S) by X-ray diffraction analysis on a single-crystal. (C) 2010 Elsevier Ltd. All rights reserved.