Gluconolactone reduction

This enzyme [EC 1.1.1.49] catalyzes the NADP -depen-dent reduction of o-glucose 6-phosphate that yields 6-phospho-D-gluconolactone, NADPH, and a proton. 

This procedure could in principle open the way, inter alia, to the phosphono analog of D-glucose 1-phosphate simply by reacting the gluconolactone 56 with LiCH2PO(OMe)2 and then reducing Ae obtained lactol 59. Unfortunately the lactol phosphonate 59 was inert to this reduction (Scheme 16). 

We did not explore the first of these two approaches too deeply. The synthesis of the epoxide 76, an ideal partner for the alkylation of any trisaccharide amine, was daunting and seemingly difficult but there was available in the literature an excellent route to the enone 77 from tetra-O-benzyl-D-gluconolactone 38 [53]. However, earlier work by Kuzuhara suggested that any reductive amina-tion of the enone 77 would probably proceed in low yield and certainly give a mixture of diastereoisomeric amines [54]. We did prepare the amine 78, via the azide 79, but the amine 78 would not condense with the enone 77 to give the... 

Reductions. An enantioselective reduction of symmetrical diacetylarenes (e.g., 2,6-diacetylpyridine) is accomplished with baker s yeast. a-Functionalized ketones such as l-methanesulfonyl-2-alkanones and P-keto esters give chiral alcohols. Significantly, baker s yeast grown under limited oxygen effects reduction to selectively furnish o-hydroxy esters, whereas on slow addition of the keto esters to ordinary yeast in the presence of gluconolactone the L-hydroxy esters are produced. 

Regarding the final coupling to the C-disaccharide, the dibromo olefin was converted, in situ, to an acetylenic anion utilizing butyllithium. Addition of this species to tetra-O-benzyl gluconolactone followed by reduction of the hemiketal afforded the final product in approximately 80% yield for the two steps. 

Some oxidoreductases require expensive cofactors, such as NADH. This requires continuous regeneration of the cofactor in a separate enzymatic reaction using a sacrificial substrate. Nanofiltration membranes have been used to separate the two enzyme systems.256 A sulfonated poly-sulfone nanofiltration was used in the reduction of fructose to mannitol, using glucose to gluconolactone to regenerate the NADH. 

Synthesis from o-gluconolactone D-Gluconolactone was converted to 1-deoxymannojirimycin (2) via introduction of an azide group at C-2, with retention of configuration as in (Scheme 9). Reduction of 47 followed by protection of the... 

The glycosidic spiroketal (16) was formed in good overall yield by cyclisation of the strategically functionalised hemiketal (15), obtained from perbemylated gluconolactone (14) as shown in Scheme 2. Although formally the cyclisation is not reductive, the presence... 

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