Because 1, as its sodium salt, is the sweetest of the three isomers, a technically feasible synthesis based on the above dehydrogenation reaction was worked out starting from readily available methyl thioglycolate and methyl acrylate (see Scheme I). The literature known preparations of methyl tetrahydro-4-oxothiophene-3-carboxylate (12) 13J6 yielded a mixture of isomers, 3, 4-and 2, 3-keto esters, which could not be easily separated by ...
