Dihydroxyacetone phosphate analogs

Figure 15 Substrate quality of dihydroxyacetone phosphate analogs [93,102,103].

Figure 10.20 Substrate analogs of dihydroxyacetone phosphate accessible by the CPO oxidation method, and spontaneous, reversible formation of arsenate or vanadate analogs of dihydroxyacetone phosphate/n s/tu for enzymatic aldol additions.

In analogy with the D-fructose D-glucose interconversion, dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphate can equilibrate by way of an enediol intermediate. 

Fructose 1,6-biphosphate aldolase from rabbit muscle in nature reversibly catalyzes the addition of dihydroxyacetone phosphate (DHAP) to D-glyceraldehyde 3-phosphate. The tolerance of this DHAP-dependent enzyme towards various aldehyde acceptors made it a versatile tool in the synthesis of monosaccharides and sugar analogs [188], but also of alkaloids [189] and other natural products. For example, the enzyme-mediated aldol reaction of DHAP and an aldehyde is a key step in the total synthesis of the microbial elicitor (—)-syringolide 2 (Fig. 35a) [190]. 

Affinity labels are molecules that are structurally similar to the substrate for the enzyme that covalently modify active site residues. They are thus more specific for the enzyme active site than are group-specific reagents. Tosyl-l-phenylalanine chloromethyl ketone (TPCK) is a substrate analog for chymotrypsin (Figure 8.21). TPCK binds at the active site and then reacts irreversibly with a histidine residue at that site, inhibiting the enzyme. The compound 3-bromoacetol is an affinity label for the enzyme triose phosphate isomerase (TIM). It mimics the normal substrate, dihydroxyacetone phosphate, by binding at the active site then it covalently modifies the enzyme such that the enzyme is irreversibly inhibited (Figure 8.22). 

Figure 8.22. Bromoacetol Phosphate, an Affinity Label for Triose Phosphate Isomerase (TIM). Bromoacetol phosphate, an analog of dihydroxyacetone phosphate, binds at the active site of the enzyme and covalently modifies a glutamic acid residue required for enzyme activity.

NaBH4 reduction with the help of CeCl3 -7H20 to obtain threo derivatives 232 (O Scheme 61). An enzymatic route for the synthesis of L-fucose analogs modified at the non-reducing end is reported by Fessner et al. [86], Using 2-Hydroxy-2-methylpropanal 233 and dihydroxyacetone phosphate 234 as substrates, branched fucose derivative 237 has been prepared via recombinant L-fuculose 1-phosphate aldolase (FucA) and L-fucose ketol isomerase (Fuel) in E. coli (O Scheme 62). 

The reactions that follow are analogous to those described for the second form of fermentation. That is, since the acetaldehyde is unavailable as an acceptor for DPNH, the latter can be used in reducing dihydroxyacetone phosphate to glycerol phosphate, which finally yields glycerol. The total equation can be expressed as follows. 

Fessner et al.[256] developed an efficient method for the synthesis of L-fucose analogs modified at the nonpolar terminus by means of L-fucose isomerase and l-fuculose 1-phosphate aldolase from E. coli. Various L-fucose analogs bearing linear or branched aliphatic side chains were prepared in about 30% overall yield with hydroxyaldehyde precursors and dihydroxyacetone phosphate as the starting materials (Fig. 17-32). 

Figure 5. Structures and mechanisms in aide-lase-Mn-substrate bridge complexes A. acetol phosphate, B. dihydroxyacetone phosphate Mechanism C is proposed for animal aldolases by analogy with A and B (from Ref, 22)...

The conversion of glucose-6-phosphate to fructose-6-phosphate is analogous to the conversion of glyceraldehyde-3-phosphate to dihydroxyacetone phosphate. Both of these isomerization reactions interconvert an aldose and a ketose. Key features of the those phosphate isomerase mechanism include the hydrogen transfer between carbon 2 and carbon f (intramolecular oxidation/reduction), and the enediol intermediate (Figure... 

Dihydroxyacetone phosphate-dependent aldolases (DHAP-aldolases) have been used widely for preparative synthesis of monosaccharides and sugar analogs (Fessner and Walter 1997 Wymer and Toone 2000 Silvestri et al. 2003). Among them, RAMA RhuA and FucA from E. coli are the most available aldolases, especially the former which was one of the first to be commercialized (Fessner and Walter 1997 Takayama et al. 1997). In many of the chemo-enzymatic strategies they are involved, the biocatalytic aldol addition to the configuration of the newly stereogenic centers is fixed by the enzyme. However, pertinent examples have been reported in which... 

W. D. Fessner and G. Sinerius, Enzymes in organic synthesis. 7. Synthesis of dihydroxyacetone phosphate (and isosteric analogs) by enzymic oxidation Sugars from glycerol, Angew. Chem., 106 (1994) 217-220. 

Fructose-b/fphosphate aldolase, aldolase (EC 4.1.2.13) a tetrameric lyase which reversibly cleaves fructose l,6-f>irphosphate into the two triose phosphates, dihydroxyacetone phosphate and o-glyceral-dehyde phosphate. The reaction is analogous to the aldol condensation (CH3CHO + CH3CHO -> CH3-CHOH-CH2-CHO), hence the name of the enzyme. The equilibrium concentrations are 89% fructose huphosphate and 11 % triose phosphate. The enzyme catalyses the condensation of a number of aldehydes with dihydroxyacetone phosphate, and can also cleave fructose 1-phosphate. Liver aldolase (aldolase B, M, 156,000, 4 subunits of A/, 39,000) cleaves fructose l,6-6isphosphate and fructose 1-phosphate at nearly the same rate. Muscle aldolase (aldolase A, M, 1, 000,4 subunits of M 41,000, pi 6.1), however, is more active with the hirphosphate. Aldolase from yeast is inhibited by cysteine, and reactivated by Fe, Zii and Co. Spinach leaf aldolase has a M, of only 120,000 (M, of subunits 30,000). 

Triosephosphate isomerase, for example, catalyzes the interconversion of glyceraldehyde 3-phosphate and dihydroxyacetone phosphate with fccat values that vary with pH, whereas is pH independent in the neutral range. This behavior appears consistent with mechanisms in which the enzyme combines with either monoanionic or dianionic forms of the substrate with similar affinity, but only the latter forms a productive complex, ES , which goes on to form products. Unlike an ordinary substrate analog, a transition-state analog for this reaction would be expected to be bound tightly only as a dianionic species, and this appears to be the case for the inhibitor 2-phosphoglycolic acid. ... 

These compounds are close structural analogs of dihydroxyacetone phosphate, differing only in replacement of the hydroxyl with a halogen. The rationale for designing haloacetol phosphates was much the same as that which led Meloche to believe that bromopyruvate would be a likely affinity label for kdGtP aldolase. Reactions catalyzed by both... 

Here we recount the latest research on chemoenzymatic multistep and cascade strategies for the synthesis of iminocyclitols, carbohydrates, and deoxysugars from N-protected ami noaldehydes, hydroxyaldehydes, and simple alkylaldehydes, respectively. The key step in all of them is the stereoselective aldol addition reaction of dihydroxyacetone phosphate (DHAP) and its unphosphorylated analogs to the acceptor aldehydes using DH AP-dependent and dihydroxyacetone- (DH A)-utilizing aldolases, respectively, as biocatalysts. 

Substrate analogs of dihydroxyacetone phosphate accessible by the GPO oxidation method. 

Spontaneous, reversible formation of arsenate and vanadate analogs of dihydroxyacetone phosphate in situ for enzymatic aldol additions. 

Glucose-6-P is then isomerized by phosphohexose isomerase to fructose-6-P (making up 30% of the equilibrium mixture). Another kinase phosphorylates the 1-position and the resulting fructose diphosphate is cleaved in an equilibrium reaction to two trioses, namely dihydroxyacetone phosphate (C-1 to C-3) and glyceral-dehyde phosphate (C-4 to C-6). The equilibrium mixture is composed of 89% hexose and 11% triose (under the conditions of Meyerhof s measurements) condensation, therefore, is the preferred (= exergonic) reaction. The reaction is analogous to the aldol condensation described in organic chemistry (Chapt. 1-2, XV-5). Catalysis of the reverse reaction by the enzyme aldolase is explained by the fact that enzymes always catalyze up to the equilibrium. ... 

Bischofberger N, Waldmann H, Saito T et al (1988) Synthesis of analogs of 1,3-dihydroxyacetone phosphate and glyceraldehyde 3-phosphate for use in studies of fructose-1,6-diphosphate aldolase. J Org Chem 53 3457-3465... 

Figure 14 Enzymatic in situ generation of dihydroxyacetone phosphate (or an isosteric phos-phonate analog) for stereoselective aldol reactions using DHAP aldolases [102].

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