Hexose 3-deoxy-4,5-0-isopropylidene

Deoxy-D-jcylo hexose 6-(dihydrogen phosphate) (21) has also been synthesized (2) the reaction sequence makes use of 3-deoxy l 2,5 6-di-O-isopropylidene D-galactofuranose (16), a compound that can be easily prepared from D-glucose (2, 60). The mono-isopropylidene derivative (17) formed by partial hydrolysis of the di-ketal is converted into the 6-tosylate (18) by reaction with one molar equivalent of p-toluenesulfonyl chloride. From this the epoxide (19) is formed by reaction with sodium methoxide. Treatment of the anhydro sugar with an aqueous solution of disodium hydrogen phosphate (26) leads to the 6-phosphate (20)... 

In the mass spectrum (Figure 8) of the corresponding ketal of 5-deoxy-D-xt/Zo-hexose, 5-deoxy-l,2-0-isopropylidene-D- rt/Zo-hexofuranose (11), the peak from C-4-C-5 cleavage, m/e 159, is of minor relative intensity. Since the ions at m/e 159 are the same from both isomers, 10 and 11, the intensity difference must be attributable to the lower stability of the primary radical formed from C-5 of 11 compared with the secondary radical from 10 ... 

Anhydro-3-deoxy-l,2-0-isopropylidene-a-D-x //o-hexofuranose— 3-deoxy-D-x /io-hexose 6-phosphate.207... 

The synthesis of methyl (methyl 3-deoxy-D-ara/uno-heptulopyranosid)-onate (124) is shown in Scheme 11. 2-Deoxy-D-ura/uno-hexose (125) is converted into the propylene dithioacetal (126) which reacts with acetone to give 2-deoxy-3,4 5,6-di-<9-isopropylidene-D-c -c//vHohexose propylene dithioacetal (127). Treatment of 127 with n-butyllithium is followed by reaction with methylchloroformiate and removal of the dithioacetal with A-bromo-succinimide gives 120. Removal of the isopropylidene groups afforded 124.312... 

Methyl 4,6-0-benzylidene-3-deoxy-a-D-ribo-hexopyranoside (56) was benzoylated, debenzylidenated, and partially p-toluenesulfon-ylated to 57 this was converted into 58 by reaction with sodium iodide, followed by catalytic reduction. The methanesulfonate of 58 was converted into 59 by reaction with sodium azide in N,N-dimethylformamide, and 59 was converted into 4-azido-3,4,6-trideoxy-a-D-xylo-hexose (60) by acetolysis followed by alkaline hydrolysis. Reduction of 60 with borohydride in methanol afforded 61, which was converted into 62 by successive condensation with acetone, meth-anesulfonylation, and azide exchange. The 4,5-diazido-3,4,5,6-tetra-deoxy-l,2-0-isopropylidene-L-ara/uno-hexitol (62) was reduced with hydrogen in the presence of Raney nickel, the resultant diamine was treated with phosgene in the presence of sodium carbonate, and the product was hydrolyzed under acidic conditions to give 63. The overall yield of 63 from 56 was 4%. The next three reactions (with sodium periodate, the Wittig reaction, and catalytic reduction) were performed without characterization of the intermediate products, and gave (+)-dethiobiotin methyl ester indistinguishable from an authentic sample thereof prepared from (+)-biotin methyl ester. 

Deoxy-6-thio-D-a yfo-hexose forms a 1,6-anhydro compound analogous to 270. S-Acetyl-5-deoxy-l,2-0-isopropylidene-6-thio-a-D-xyZo-hexofuranose is obtained either by nucleophilic displacement on the corresponding 6-p-tolylsulfonyloxy compound with potassium thioacetate or by the photochemical addition of thioacetic acid to... 

Brimacombe and How reduced methyl 3,4-0-isopropylidene-2,6-di-O-p-tolylsulfonyl-a-D-galactopyranoside with lithium aluminum hydride in tetrahydrofuran, to provide methyl 3,4-O-isopropylidene-2-0-p-tolylsulfonyl-a-D-fucopyranoside in 54% yield. In later reductions of closely related compounds, the solvent chosen was ether-benzene methyl 3-0-benzyl-2-deoxy-6-0-p-tolylsulfonyl-a-D-Ii/xo-hexopyranoside afforded the corresponding 6-deoxy compound which, on methylation, debenzylation, and acid hydrolysis, gave 2,6-dideoxy-4-O-methyl-D-Zi/Jco-hexose (chromose A). An improved synthesis of this sugar involved the reduction, in ether—benzene (1 1), ofmethyl 2-deoxy-4-0-methyl-3,6-di-0-p-tolylsulfonyl-a-D-/i/xo-hexopyranoside to methyl 2,6-dideoxy-4-0-methyl-a-D-Z /xo-hexopy-ranoside in 25% yield a synthesis of 3-0-acetyl-2,6-dideoxy-D-Z /xo-hexose (chromose D) was effected by way of reduction in ether-benzene (2 1) of methyl 2-deoxy-6-0-p-tolylsulfonyl-a-D-Zyxo-hexo-pyranoside to the corresponding 6-deoxy compound in 27% yield, followed by partial acetylation and acid hydrolysis. 

Total syntheses of 3-deoxy-D-n o and 3-deoxy-D-arafci o-hexose have been realized via the cross-aldolization of 2,3-0-isopropylidene-D-glyceraldehyde (R)-37 and 1,1-dimethoxyace-tone (O Scheme 67). The key step of the synthesis is the diastereoselective reduction of one of the aldols 171 via boron chelates. Treatment of 171 with triisobutylborane, and then with NaBH4 gives syn-, 3- (173) and awft-l,3-diol 174 in a ratio 95 5. Acidic hydrolysis of 173 provides 3-deoxy-D-n7 o-hexose. If aldol 171 is treated first with an equimolar amount of aluminum triisopropoxide, diol 174 is obtained in 62% yield (together with 15% of 173). Compound 174 is converted then into 3-deoxy-D-arafci o-hexose [307]. 

Hydrolysis of the known 3,5-0-benzylidene-6-deoxy-l,2-0-iso-propylidene-a-D-xt/Zo-hex-5-enofuranose affords a route to the antibiotic sugar 6-deoxy-D-xy(o-hexos-5-ulose 143 the synthesis of 5-deoxy-l,2-0-isopropylidene-6-0-trityl-a-D-xt/(o-hex-5-enose (79, R = H, R = OTr) has been discussed further,144 and, on hydrogenation, the compound, affords crystalline 5-deoxy-l,2-0-isopropylidene-a-D-xy/o-hexose.145... 

Fuganti and co-workers used 2R 3R-tartaric acid for the synthesis of 3-benzamido-2,3,6-trideoxy-L-xy/o-hexose (393). The acid was converted according to a known procedure into 2,3-0-isopropylidene-4-0-p-toluenesulfonyl-L-threitol (388). Reduction of 388 with lithium aluminum hydride gave 4-deoxy-... 

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