Halogenated enolates. Synthesis of 2-deoxypentose derivatives from D-glyceraldehyde

Abstract

The reaction of alkyl dihalogenoacetate magnesium enolates (1) with 2,3-O-isopropylidene-D-glyceraldehyde (3) to give the hydroxy-esters (4) and (5) has been studied. We found that the production of the erythro-isomer (4) is favoured, in agreement with theoretical models. An erythro: threo ratio of 7 : 3 was obtained with the enolate (1b). This condensation may be an alternative to the lithioacetate condensation method after removal of halogen by Raney nickel- or tributyltin hydride-reduction. The structures of the different products were established after lactonisation which proceeded in good yield. This method constitutes a new entry to 2-deoxy-2-halogeno- and 2-deoxypentono-1,4-lactones.