A two-step strategy for the preparation of 6-deoxy-l-sorbose.

A two-step enzymatic strategy for the efficient and convenient synthesis of 6-deoxy-l-sorbose was reported herein. In the first reaction step, the isomerization of l-fucose (6-deoxy-l-galactose) to l-fuculose (6-deoxy-l-tagatose) catalyzed by l-fucose isomerase (FucI), and the epimerization of l-fuculose to 6-deoxy-l-sorbose catalyzed by d-tagatose 3-epimerase (DTE) were coupled with the targeted phosphorylation of 6-deoxy-l-sorbose by fructose kinase from human (HK) in a one-pot reaction. The resultant 6-deoxy-l-sorbose 1-phosphate was purified by silver nitrate precipitation method. In the second reaction step, the phosphate group of the 6-deoxy-l-sorbose 1-phosphate was hydrolyzed with acid phosphatase (AphA) to produce 6-deoxy-l-sorbose in 81% yield with regard to l-fucose.

Enzymatic synthesis of D-sorbose and D-psicose with aldolase RhaD: effect of acceptor configuration on enzyme stereoselectivity.

It was previously reported that DHAP-dependent aldolase RhaD selectively chooses L-glyceraldehyde from racemic glyceraldehyde to produce l-fructose exclusively. Contrastingly, we discovered that D-glyceraldehyde is also tolerated as an acceptor and the stereoselectivity of the enzyme is lost in the corresponding aldol addition. Furthermore, we applied this property to efficiently synthesize two rare sugars D-sorbose and D-psicose.

A facile synthesis of 1,6-dideoxynojirimycin from L-sorbose.

A practical synthesis of 1,6-dideoxynojirimycin, a potent glycosidase inhibitor, starting from L-sorbose, is described.

Conformational evaluation of some 4-deoxyhex-4-enopyranose derivatives and their use in the preparation of a previously undescribed class of 3-thio-L-sorbopyranosides and their 6-C-methoxy analogues.

A new series of thio-substituted sugars were synthesised relying on the totally regio- and stereoselective cycloaddition of 4-deoxyhex-4-enopyranose derivatives to 'in situ' generated oxothiones. Conformational studies of the above unsaturated sugars showed a marked prevalence of the all-axial conformer.

Steric and electronic effects in the formation of dihexulose dianhydrides. Reaction of racemic sorbose in anhydrous hydrogen fluoride and a facile synthesis of D-sorbose.

Treatment of DL-sorbose with anhydrous hydrogen fluoride gave a high yield of alpha-D-sorbopyranose alpha-L-sorbopyranose 1,2':2,1'-dianhydride. Similarly a mixture of D-fructose and D-sorbose gave a good yield of beta-D-fructopyranose alpha-D-sorbopyranose 1,2':2,1'-dianhydride. The formation of these products compared to the more complicated mixtures of compounds obtained by treatment of L-sorbose or D-fructose with hydrogen fluoride, is discussed in terms of conformations, and steric and electronic factors.

Study of 1-deoxy-1-(indol-3-yl)-L-sorbose, 1-deoxy-1-(indol-3-yl)-L-tagatose, and their analogs.

Alkaline degradation of the ascorbigen 2-C-[(indol-3-yl)methyl]-alpha-L-xylo-hex-3-ulofuranosono-1,4-lactone (1a) led to a mixture of 1-deoxy-1-(indol-3-yl)-L-sorbose (2a) and 1-deoxy-1-(indol-3-yl)-L-tagatose (3a). The mixture of diastereomeric ketoses underwent acetylation and pyranose ring opening under the action of acetic anhydride in pyridine in the presence of 4-dimethylaminopyridine (DMAP) with the formation of a mixture of (E)-2,3,4,5,6-penta-O-acetyl-1-deoxy-1-(indol-3-yl)-L-xylo-hex-1-enitol (4a) and (E)-2,3,4,5,6-penta-O-acetyl-1-deoxy-1-(indol-3-yl)-L-lyxo-hex-1-enitol (5a), which were separated chromatographically. Deacetylation of 4a or 5a afforded cyclised tetrols, tosylation of which in admixture resulted in 1-deoxy-1-(indol-3-yl)-3,5-di-O-tosyl-alpha-L-sorbopyranose (12a) and 1-deoxy-1-(indol-3-yl)-4,5-di-O-tosyl-alpha-L-tagatopyranose (13a). Under alkaline conditions 13a readily formed 2-hydroxy-4-hydroxymethyl-3-(indol-3-yl)cyclopenten-2-one (15a) in 90% yield. Similar transformations were performed for N-methyl- and N-methoxyindole derivatives.

A reinvestigation of the synthesis and revision of spectral data of 1,2-O-isopropylidene-α-l-sorbofuranose, 1,2:4,6-di-O-isopropylidene-α-L-sorbofuranose and derivatives.

Mono- and di-O-isopropylidene-l-sorbofuranose derivatives are important starting materials for the synthesis of modified sugars and useful chiral compounds. However, several inconsistencies in the spectral data of these compounds and erroneous structural assignments have been noted in the literature. The unambiguous synthesis of 1,2:4,6-di-O-isopropylidene-α-L-sorbofuranose and derivatives of 1,2- and 2,3-O-isopropylidene-α-L-sorbofuranoses has been achieved and definitive spectral data on these compounds are provided.