SYNTHESIS AND STEREOCHEMISTRY OF CHIRAL 1,3-DIOXANIC COMPOUNDS OBTAINED FROM ALPHA-ALKYLATED BETA-KETOESTERS

1,3-Dioxanic compounds were obtained by the ketalisation reaction of s ome alpha-alkylated beta-ketoesters. The conformational analysis by me ans of H-1- and C-13-nmr investigations showed the anancomeric structu re of the compounds. The axial or the equatorial position of the group s was inferred by N.O.E. experiments. The influence of the chiral carb on atom of the esteric group located at C-2 was studied using the dias tereotopicity of the protons and of the carbon atoms recorded in high field nmr spectra.