engleski

Convenient Entry to α-Amino-β-hydroxy-γ-methyl Carboxylic Acids. Diastereoselective Formation and Directed Homogeneous Hydrogenation of 3-(3-Aryl-1-hydroxy-2- methylprop-2-enyl)-1,4-benzodiazepin-2-ones

Aldol reaction of 7-chloro-1, 3-dihydro-1-methyl- 5-phenyl-2H-1, 4-benzodiazepin-2-one (1) with 4- substituted-2-methyl-cinnmaldehydes 2-5 affords a mixture of threo and erythro 7-chloro-1, 3- dihydro-3-(1-hydroxy-3-aryl-2-methyl-allyl)-1- methyl-5-phenyl-2H-1, 4-benzodiazepin-2-ones 6-13. Chromatographically separated threo (6, 8, 10, 12) and erythro (7, 9, 11, 13) diastereomers are submitted to directed homogeneous hydrogenation catalyzed by [Rh(I)-(DIPHOS-4)(COD)]ClO4 complex. From erythro racemates 9, 11, and 13 erythro, erythro (16, 20, 24) and erythro, threo diastereomers (17, 21, 25) were obtained in the ration from 30:70 to 20:80 (HPLC), and have been separated by chromatography. From threo racemates 8, 10 and 12 threo, threo and threo, erythro diastereomers were obtained in the approx. ratio 25:75 (1H-NMR. Assignment of relative configurations of all diastereomers is based on 1H-NMR data and X-ray structure determination for 21. Hydrolysis of 21 afforded diastereomerically pure N-Cbz derivative of  -amino- -hydroxy- - methyl carboxylic acid 27, representative of the novel group of polysubstituted  -amino- -hydroxy carboxylic acids.

Aldol reaction

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