Use of two-dimensional spectroscopy for the determination of the stereochemical structure of 3-carbethoxy-2-methyl-7a-(4-carbethoxy-5-methyl-2-furyl)-3a,4,5,6,7,7a-hexahydrobenzofuran

Abstract

Homo- and heteronuclear two-dimensional correlation spectra, as well as J-resolved spectra with selective excitation, were used to analyze in detail the stereochemical structure of 3-carbethoxy-2-methyl-7a-(4-carbethoxy-5-methyl-2-furyl)-3a,4,5,6,7,7a-hexahydrobenzofuran, obtained by the reaction of cyclohexenyl-acetylene with acetoacetic ester in the presence of a manganese(III) salt. It was shown that the use of the long-range 13C-1H coupling constants is a very effective method for the determination of the conformation of the molecule. The stereochemical aspects of the reaction of cyclohexenylacetylene with acetoacetic ester is discussed.