SYNTHESES AND OPTICAL ROTATORY DISPERSION STUDIES OF (S)-5-(2'-PENTYL)BARBITURIC ACID DERIVATIVES

The syntheses of several (S)-5-(2ʹ-pentyl)barbituric acid derivatives are reported and their optical properties have been investigated. Although the ultraviolet spectra of (S)-(-)-5-ethyl-5-(2ʹ-pentyl)barbituric acid (IIa) shows only one maximum under the conditions studied, optical rotatory dispersion measurements have shown two Cotton effects. Some pH dependent optical rotatory dispersion studies indicate that the lower wavelength Cotton effect is the result of a π-π* transition and the higher wavelength Cotton effect is of type n-π*. The π-π* Cotton effect is positive and the n-π* Cotton effect is negative. The ultraviolet spectrum of the monosubstituted barbituric acid, (S)-(+)-5-(2ʹ-pentyl)barbiturie acid (IIc), in acid solution showed one maximum and the optical rotatory dispersion curve in the same solvent showed a negative π-π* low wavelength and a positive n-π* high wavelength Cotton effect. These results show that the biologically active IIa has optical rotatory dispersion properties greatly different from those of the biologically inactive IIc. These results are discussed in relation to the differences in the structure of these two compounds. © 1969, American Chemical Society. All rights reserved.