Vitamin‐C‐ and isovitamin‐C‐derived chemistry. Part I. Synthesis of 2,3‐dideoxy derivatives of the Ascorbic acids

5,6‐ O ‐Isopropylidene‐L‐gulono‐ and ‐D‐mannono‐1,4‐lactones are converted into 2‐(dimethylamino)‐1,3‐dioxolane derivatives on treatment with N,N ‐dimethylformamide dimethyl acetal in chloroform with azeotropic removal of the methanol thus formed. Quaternisation of the products with iodomethane, followed by thermal decomposition yields the corresponding C(4)‐substituted enantiomeric butenolides. Some aspects of the reactions, the characterisation of the products, and further transformations are described.