Reactions of hydriodic acid with aldonolactones and n-alkanolactones. Interconversions between lactones and iodocarboxylic acids

Aldonolactones containing from four to eight carbon atoms, and lactones of the related monohydroxy-n-alkanoic acids, were subjected to reaction with 57% hydriodic acid at 125 °C. As in the classical studies of Kiliani, the reduction of D-glycero-D-ido-heptono-1,4-lactone yielded mainly γ-heptanolactone. Analogously, the corresponding γ-alkanolactones were obtained as major products from the 1,4-lactones of the D-xylono-, D-allono-, and D-erythro-L-talo-octono configuration. Monoiodo-n-alkanoic acids were also formed in admixture with the lactones in all of these reactions. D-Erythrono-1,4-lactone was unique among the aldonolactones in that it led only to an acid, i.e., 3-iodo-n-butanoic acid. The latter was also the product of the non-reductive reaction of hydriodic acid with β-butyrolactone whereas, by contrast, γ-butyrolactone afforded 4-iodobutanoic acid. Among compounds in the five to eight carbon series, it was found that under conditions close to equilibrium the ratio of lactone to iodoacid decrease...