BETA-ELIMINATION OF PROTECTED ALDONO-1,4-LACTONES AS A GENERAL-APPROACH TO THE SYNTHESIS OF 2-KETO-3-DEOXYALDONIC ACIDS CONTAINING 4 TO 6 CARBON-ATOMS

The well-known beta-elimination of protected aldonolactones is used fo r the synthesis of the short-chain 2-keto-3-deoxyaldonic acids 1-4 con taining four to six carbon atoms. The key step is the facile beta-elim ination step which generates the desired 2-keto-3-deoxy acids as prote cted enol 1,4-lactones in excellent yields. Smooth deprotection then l eads to the 2-keto-3-deoxyaldonic acids. In the case of the protected D-galactono-1,4-lactone 6 an epimerisation is observed during the elim ination process. This enables the synthesis of both 2-keto-3-deoxy-D-h exonic acids with either D-erythro (1) or D-threo (2) configuration in good to excellent yields in only three steps starting with commercial ly available D-galactono-1,4-lactone (5).