Four oxoindole-linked α-alkoxy-β-amino acid derivatives

Four structures of oxoindolyl α-hydroxy-β-amino acid derivatives, namely, methyl 2-{3-[(tert-butoxycarbonyl)amino]-1-methyl-2-oxoindolin-3-yl}-2-methoxy-2-phenylacetate, C24H28N2O6, (I), methyl 2-{3-[(tert-butoxycarbonyl)amino]-1-methyl-2-oxoindolin-3-yl}-2-ethoxy-2-phenylacetate, C25H30N2O6, (II), methyl 2-{3-[(tert-butoxycarbonyl)amino]-1-methyl-2-oxoindolin-3-yl}-2-[(4-methoxybenzyl)oxy]-2-phenylacetate, C31H34N2O7, (III), and methyl 2-[(anthracen-9-yl)methoxy]-2-{3-[(tert-butoxycarbonyl)amino]-1-methyl-2-oxoindolin-3-yl}-2-phenylacetate, C38H36N2O6, (IV), have been determined. The diastereoselectivity of the chemical reaction involving α-diazoesters and isatin imines in the presence of benzyl alcohol is confirmed through the relative configuration of the two stereogenic centres. In esters (I) and (III), the amide group adopts an anti conformation, whereas the conformation is syn in esters (II) and (IV). Nevertheless, the amide group forms intramolecular N-H···O hydrogen bonds with the ester and ether O atoms in all four structures. The ether-linked substituents are in the extended conformation in all four structures. Ester (II) is dominated by intermolecular N-H···O hydrogen-bond interactions. In contrast, the remaining three structures are sustained by C-H···O hydrogen-bond interactions.