Ulose synthesis

Derivatives of 6-deoxy-hex-5-enopyranosides are important intermediates in the synthesis of dicarbonyl sugars, namely hexos-5-uloses. For... 

The presence of a dichloromethylene group at the anomeric center of 82 facilitates proton abstraction at C-3 by a strong base (77), aifording the 4-deoxyglycos-3-ulose derivative 83. Reduction of the dichloromethylene group by Raney nickel gave a 1-C-methyl derivative with high stereospecificity, which opens the way to a series of 2,5-anhydro-l-deoxyalditols. Compound 83 was the key intermediate for the synthesis (78) of tosyl L-(+)-epi-muscarine (84a) and tosyl L-(+)muscarine (84b). 

D-Glucose 6-phosphate is converted enzymically into L-wyo-inositol 1-phosphate (20) in a process which requires NAD+. The base-catalysed cyclization of d-xylo-hexos-5-ulose 6-phosphate (21), followed by reduction with borohydride, leads to (20) and epi-inositol 3-phosphate (22) (Scheme 3).59 This has been put forward as a chemical model for the enzymic synthesis. The phosphorylation of inositols with polyphosphoric acid has been described80 and the p-KVs of inositol hexaphosphate have been determined by 31P n.m.r.61... 

O. Varela, G. M. de Fina, and R. M. de Lederkremer, The reaction of 2-hydroxyglycal esters with alcohols in the presence of N-iodosuccinimide, stereoselective synthesis of a anomers of alkyl 3-deoxyhex-2-enopyranosides and 3,4-dideoxyhex-3-enopyranosid-2-uloses, Carbohydr. Res., 167 (1987) 187-196. 

Oxidation by stoich. RuOyCCl of five xylofuranosides gave the corresponding 2- and 3-nloses (Table 2.3) [315], and that of 5-0-benzoyl-1,2-0-isopropylidene-a-D-xylofnranose by the reagent to the -a-D-e yt/iro-pentafuranos-3-ulose formed part of a synthesis of branched-chain 3 -C-methyladenosine [316, 322]. Likewise the cyclopropyl-substituted 4-C-cyclo-propyl-l,2-0-isopropyl-idene-D-xylo-tetrafuranose was converted to the 3-ulose [314]. 

Stoicheiometric RuOyCCl was also used to oxidise several furanoses, partially acylated glycosides and l,4 3,6-dianhydrohexitols [317] pyranosides to pyrano-siduloses [313] methyl 2,3,6-tri-O-benzoyl-a-D-glucopyranoside and its C-4 epimer to the a-D-xy/o-hexapyranosid-4-ulose (Table 2.3) [317], and methyl 2,3,6-trideoxy-a-D-e 7f/tro-hexapyranoside to the -a-D-,g/yceri9-hexa-pyranosid-4-ulose, an intermediate in the synthesis of forosamine [318], It was also used to oxidise benzyl 6-deoxy-2,3-0-isopropylidene-a-L-mannopyranoside to the a-L-/yxo-hexapyranosid-4-ulose [319] and for oxidation of isolated secondary alcohol functions, e.g. in the conversion of l,6-anhydro-2,3-0-isopropylidene-P-D-man-nopyranose to the-P-D-/yxo-hexa-pyranos-4-ulose mannopyranose (Fig. 2.16, Table 2.3 [20, 320, 324]). 

A mutant strain of Escherichia coli Y-10, defective in L-rhamnose synthesis, accumulates109 a considerable amount of thymidine diphosphate sugars. Three of them were identified110 as the esters of thymidine 5 -pyrophosphate with 6-deoxy-a-D-xyZo-hexopyranos-4-ulose (28), 6-deoxy-D-glucose, and D-fucose. The fourth component was found to be a 4-acetamido-4,6-dideoxy-D-galactose derivative111,112 (29) it occurs also in Pasteurella pseudotuberculosis102 and its... 

For such hex-3-enopyranosid-2-uloses as 127 or 129, reaction with lithium dimethylcuprate,261 or with anions of malonic ester-type, methylene components in the presence of bis(2,4-pentanedionate)-Ni(II) catalyst,263 affords, in each case, the 1,4-addition products (128 and 130, respectively), in which the branching group is in the axial orientation. The methyl-branched pyranosides 126 and 128, readily accessible in this way, have been of use as chiral precursors for the synthesis of multistria-tins.264-285... 

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