Synthesis of all stereoisomers and some congeners of isocytoxazone

Article abstract of DOI:10.1055/s-2003-37353

cis-Isocytoxazone 2a and trans-isocytoxazone 2b, structural isomers of the antiasthmatic agent cytoxazone (-)-1, and their 5-substituted congeners 23-28 have been prepared. Aldol reaction of para-substituted benzaldehydes with 7-chloro-1-methyl-5-phenyl-1,4-benzodiazepin-2-one, followed by separation of diastereomeric racemates afforded 3-10. Acid-catalyzed 1,4-benzodiazepine ring opening, and transformation of the methyl esters of β-aryl-β-hydroxy-α-amino acids (11-16) via 4-methoxycarbonyl derivatives of 1,3-oxazolidin-2-one (17-22) and their reduction afforded the target oxazolidin-2-one derivatives 23-28. Racemic isocytoxazones 2a and 2b were prepared by an independent route starting from 4-methoxystyrene epoxide. Pure enantiomers of these diastereomeric racemates were separated by HPLC chromatography on chiral stationary phases. Their CD spectra, along with those of previously prepared enantiomers of cis-cytoxazone 1a and trans-cytoxazone 1b are discussed.