A Novel Convenient Preparation of Dihydroxyacetone Phosphate and Its Use in Enzymatic Aldol Reactions

A new preparation of the stable barium salt of 2,5-bis(phosphonooxymethvl)-2.5-diethoxv-1.4-dioxane Ba-2 is described, which bv treatment with DOWEX 50 B+ gives dihydroxyacetone ph&phate (DHAP) in high yield. DHAP prepared by this method was used for aldolase-catalyzed condensations. An increasing number of papers dealing with enzymatic aldol reactions demonstrates their synthetic utility 1,2,4 . Rabbit muscle fructose-1,6-diphosphate aldolase (EC 4.1.2.13), which has been used as a catalyst, is rather specific for dihydroxyacetone phosphate (DHAP) reacting as a nucleophile while accepting a wide variety of aldehydes as electrophiles. However, the prohibitively high costs (in 1986, the price of 1 mm01 DHAP was 175 $) of DHAP have discouraged the use of this highly stereospecific C-C-bond tormation method as an efficient preparative tool in organic synthesis. DHAP can be synthesized by enzymatic phosphorylation of dihydroxyacetone (DHA) with ATP, the latter being regenerated with some loss with acetylphosphate3. In comparison, an in situ generation of DHAP from fructose-1,6-di--phosphate in the presence of triose phosphate isomerase affords in many cases lower yields in the subsequent aldolase-catalyzed sugar synthesis4. In attempting chemical routes to DHAP, the polyfunctionality of DHA has until now required complicated multistep syntheses5. A typical a-step synthesis proceeding via the monoacetylated derivative of DHA yields the dimethyl ketal of DHAP which can be isolated as its stable cyclohexylammonium salt5. Another way6 involves first ketalating the DHA-dimer with triethyl orthoformate 7 to 1 -Phosphorylation of 1 with (Ph0)2POC1 followed by catalytic hydrogenation gives 2, isolated as its cyclohexylammonium salt6. Our attempts at reproducing a reported direct phosphorylation of DHA with POC13' resulted in complex reaction mixtures containing only small amounts of DHAP which were not useful for enzymatic aldol reactions.