D-tagatose from

In the synthesis of D-tagatose from the more common D-fructose, 1-O-benzoyl-2,3-O-isopropylidene-P-D-fructopyranose afforded two products identified as l-O-benzoyl-5-0-benzyl-2,3-0-isopropylidene-P-D-fructopyranose (97%) and its 4-O-benzyl isomer (2.8%). The skew-boat 6S4(D) conformation with an oxygen atom at C-5 adopting a quasi-equatorial position is responsible for the unexpected regioselectivity observed [136]. Conformational equilibria may also be a reason for the non-exclusive, though preferential substitution at 0-3 of benzyl 4-0-benzyl-6-deoxy-a-L-talopyranoside (9) [142]. Even in this case, however, no tri-O-benzyl derivative was formed and no starting material 9 remained, the total isolated yield of 10 and 11 being 87%. 

A synthesis of D-tagatose from D-galactose proceeds via the hexos-2-ulose derivative 212, which was obtained by oxidation under Moffatt conditions from 211 and exists as the tautomeric form 213.426... 

Chromatography has proved to be an excellent tool for the identification and isolation of carbohydrates. Both paper and partition chromatography were employed for the identification and separation of D-tagatose from the gum exudate of Sterculia setigera. Previous to that, D-psicose and L-sorbose had been placed in the absorption series listed for clay.88 Conditions for zoning keto-D-psicose pentaacetate on magnesol-celite have been described by Binkley and Wolfrom (see page 126, ref. 137). 

Definite identification of the crystalline ketohexoses could be made by x-ray diffraction methods. This was actually employed in the case of the isolation of D-tagatose from Sterculia setigera X-Ray crystallographic data for L-sorbose has been available for some time (see page 136, ref. 175). 

A few years later Griinnagel and Haas used the same approach to synthesis d-tagatose from o-galactose via the Amadori rearrangement product 1-deoxy-l-dibenzylamino-D-tagatose [70]. 

Efficient procedures for the conversion of levoglucosenone to rare sugars, e.g., D-altrose, D-allose, 4-deoxy-o-mannose, have been devised. Hydrolytic opening of the L-sorbopyranose-derived epoxide 12 with nucleophilic attack at C-4 was the key-step in the transformation of L-sorbose to L-fructose, which requires inversion of configuration at C-3 and C-4. The formation of D-tagatose from d-... 

This enzyme [EC 2.7.1.11], also known as phosphohexo-kinase and phosphofructokinase 1, catalyzes the reaction of ATP with D-fructose 6-phosphate to produce ADP and D-fructose 1,6-bisphosphate. Both D-tagatose 6-phosphate and sedoheptulose 7-phosphate can act as the sugar substrate. UTP, CTP, GTP, and ITP all can act as the nucleotide substrate. This enzyme is distinct from that of 6-phosphofructo-2-kinase. See also ATP GTP Depletion... 

D-fructose 1,6-bisphosphate 2 (FruA E.C. 4.1.2.13), D-tagatose 1,6-bisphosphate 4 (TagA E.C. 4.1.2.40), L-fuculose 1-phosphate 5 (FucA, E.C. 4.1.2.17), and L-rhamnulose 1-phosphate 4 (RhuA, E.C. 4.1.2.19). From previous studies, we have DHAP aldolases with all four possible specificities readily available, we have demonstrated their broad substrate tolerance for variously substituted aldehydes, and we have investigated their stereoselectivity profile with non-natural substrates [3-6]. 

The substrate spectrum of SuSyl from yeast is well documented for a variety of acceptors [24, 29, 30]. In the series of ketoses we concluded that SuSyl favors the 3S,4R configuration because L-sorbose 4 and D-xylulose 5 are accepted and D-tagatose 6, D-psicose 7, and D-sorbose 8 are not substrates (Fig. 2.2.6.1 and... 

The ketoses D-tagatose 6 (43% relative activity) and D-ribulose 28 (24% relative activity) were identified as new acceptor substrates they are not accepted by recombinant SuSyl from yeast. However the acceptance for D-xylulose 5 is lost. The most significant changes were observed for the aldoses tested L-arabinose 14, D-xylose 12, and D-lyxose 11 are better substrates than D-fructose, with relative activities of 490%, 300%, and 151%, respectively. In the hexose series L-glucose 29 and L-rhamnose 30 were identified as new acceptor substrates, whereas the acceptance for D-and L-mannose, 16 and 21, was improved (Fig. 2.2.6.5) (Sauerzapfe and Elling, unpublished results). 

Anderson, R.L. Bissett, D.L. D-Tagatose-6-phosphate kinase from Staphylococcus aureus. Methods Enzymol., 90, 87-91 (1982)... 

Scheme 20. Multienzymatic synthesis of D-tagatose 1,6-bisphosphate and its differentiation from the /rucfo-configurated side product...

This preparation was repeated later68 and the crystalline product classified as a-D-tagatose because this crystalline sugar of the D-series mutarotated in the levo direction, namely from +2.7° to —4° (see page 112). 

D-Tagatose has recently been isolated in the crystalline condition from a natural source, namely, by acid hydrolysis of the gum exudate of the tropical tree Sterculia 8etigera,M followed by the separation of D-tagatose... 

---