INVESTIGATION OF THE PHOSPHINYL ANALOG OF ALPHA-KETOGLUTARIC ACID

It was shown by P-31 and C-13 NMR spectroscopy that methyl(3-carboxy-3 -oxopropyl)phosphinic acid (4-methylhydroxyphosphinyl-2-oxobutyric aci d) (1) and the amide (2) of the latter exist in keto forms in non-aque ous solutions. In aqueous solutions an equilibrium between the keto, g em-diol, and enol forms has been observed. The proportions of the diol and enol forms increase as the acidity of the media increases. Silyla tion of acid 1 with hexamethyldisilazane gives the tris(trimethylsilyl ) derivative of enol form (3) (Z- and E-isomers).