Separation of enantiomers of 4-aryldihydropyrimidines by direct enantioselective HPLC. A critical comparison of chiral stationary phases
摘要:
The separation of the enantiomers of 29 racemic 4-aryldihydropyrimidine-5-carboxylates (DHPMs), aza-analogs of nifedipine-type dihydropyridine calcium channel modulators, was evaluated in direct enantioselective HPLC, employing the following commercially available chiral stationary phases (CSPs): Chiralcel OD-H, ChiraDex, Chirobiotic V and T, and Whelk-O1. In addition, a 1,2-diphenyl-1,2-diaminoethane based CSP and two quinine carbamate based chiral ion exchangers were also employed. For all 29 DHPMs separation of individual enantiomers could be achieved with at least one CSP with alpha-values ranging from 1.10 to 8.67. (C) 1997 Elsevier Science Ltd.
Synthesis and reactions of biginelli compounds −5. Facile preparation and resolution of a stable 5-dihydropyrimidinecarboxylic acid.
摘要:
The synthesis of enantiomerically pure 5-dihydropyrimidinecarboxylic acids 7a,b is described. Condensation of benzyl acetoacetate with methylurea and 2-naphthaldehyde gave Biginelli compound 3b, which after methylation and removal of the benzyl group led to racemic acid 5b. Fractional crystallization of diastereomeric alpha-methylbenzylammonium salts 6a,b followed by acidification provided the desired optically pure carboxylic acids 7a,b. Conversion of 7a,b to carboxylic acid azides 8a,b, followed by Curtius rearrangement and reaction with 10-undecenol led to chiral urethanes 10a,b. The absolute stereochemistry of acids 7a,b was established by X-ray analysis of diastereomeric alpha-methylbenzylammonium-carboxylate 6c.
Synthesis and reactions of Biginelli-compounds. Part 23. Chemoenzymatic syntheses of enanttiomerically pure 4-aryl-3,4-dihydropyrimidin-2(1H)-ones
作者:Barbara Schnell、Wolfram Krenn、Kurt Faber、C. Oliver Kappe
DOI:10.1039/b006372j
日期:——
Enantiomerically pure dihydropyrimidones (DHPMs) were prepared by lipase-catalyzed enzymatic resolution of two types of activated DHPM esters. In the first model series, pivaloyloxymethyl-activated DHPM C5-esters 10a–c were resolved on an analytical scale by various lipases in two different solvent systems with selectivities E < 50. Alternatively, attachment of an acetoxymethyl residue at the N3 position of the DHPM scaffold led to activated ester 15, which was selectively cleaved by Thermomyces lanuginosus lipase (E > 200) to furnish, after deprotection, DHPMs (R)- and (S)-13 on a semi-preparative scale. Treatment of (R)-13 with trichloroacetyl isocyanate produced the antihypertensive agent (R)-SQ 32926.
Separation of enantiomers of 4-aryldihydropyrimidines by direct enantioselective HPLC. A critical comparison of chiral stationary phases
作者:Oliver P. Kleidernigg、C.Oliver Kappe
DOI:10.1016/s0957-4166(97)00214-0
日期:1997.6
The separation of the enantiomers of 29 racemic 4-aryldihydropyrimidine-5-carboxylates (DHPMs), aza-analogs of nifedipine-type dihydropyridine calcium channel modulators, was evaluated in direct enantioselective HPLC, employing the following commercially available chiral stationary phases (CSPs): Chiralcel OD-H, ChiraDex, Chirobiotic V and T, and Whelk-O1. In addition, a 1,2-diphenyl-1,2-diaminoethane based CSP and two quinine carbamate based chiral ion exchangers were also employed. For all 29 DHPMs separation of individual enantiomers could be achieved with at least one CSP with alpha-values ranging from 1.10 to 8.67. (C) 1997 Elsevier Science Ltd.
Synthesis and reactions of biginelli compounds −5. Facile preparation and resolution of a stable 5-dihydropyrimidinecarboxylic acid.
The synthesis of enantiomerically pure 5-dihydropyrimidinecarboxylic acids 7a,b is described. Condensation of benzyl acetoacetate with methylurea and 2-naphthaldehyde gave Biginelli compound 3b, which after methylation and removal of the benzyl group led to racemic acid 5b. Fractional crystallization of diastereomeric alpha-methylbenzylammonium salts 6a,b followed by acidification provided the desired optically pure carboxylic acids 7a,b. Conversion of 7a,b to carboxylic acid azides 8a,b, followed by Curtius rearrangement and reaction with 10-undecenol led to chiral urethanes 10a,b. The absolute stereochemistry of acids 7a,b was established by X-ray analysis of diastereomeric alpha-methylbenzylammonium-carboxylate 6c.