Hexopyranoses analogs

Additional n.m.r.-spectral data have been become available since about mid-1986. Further data for hexopyranosyl fluorides,as well as for 2-deoxy-2-fluoro-hexopyranoses and -hexopyranosides, " " have been reported by several groups, whereas only a few articles dealt with pento-pyranose or hexofor pento)furanose analogs " of these compounds. 

Scheme 48 Synthesis of butenolides fused to pento- or hexopyranoses and thiosugar analogs from furanos-3-nloses...

In analogy to the a-hydroxy effects in cyclohexanols (vide supra), the chemical shifts of anomeric atoms in pyranoses are often stereochemistry dependent, as seen for the C-l shifts of the following hexopyranoses in deuterium oxide41-45. 

The analog of this sugar nucleotide lacking the hydroxyl group at C-2", namely, uridine 5 -(2-deoxy-a-D-/yxo-hexopyranosyl pyrophosphate) is formed in admixture with uridine 5 -(2-deoxy-a-D-arabino-hexopyranosyl pyrophosphate) when yeasts249 or higher plants250 are treated with 2-deoxy-D-ft/xo-hexopyranose. 

The mass spectra of hexopyranose pentaacetates contain small peaks at m/e 245. An analogous peak at m/e 187 in the mass spectrum of 2-deoxy-D-... 

For the sake of convenience, the numbering of a pseudo-sugar has been used tentatively in this article in the analogous numbering of a true hexopyranose. 

A distant, sulfur analog of l,6-anhydro-2,3,4-trideoxy-j3-D-glt/cero-hexopyranose (26) is (lR,5R)-6,8-dioxa-3-thiabicyclo[3.2.1]octane (241), which was prepared by periodic acid oxidation of levoglucosan (6), followed by reduction of the resulting dialdehyde 100 to diol 242, and by p-toluenesulfonylation to 243, and replacement of the two sulfonic ester groups of 243 with sodium hydrogensulfide.731... 

K. Tadano, H. Maeda, M. Hoshino, Y. Iimura, and T. Suami, A Novel transformation of four aldoses to some optically pure pseudohexopyranoses and a pseudopentofuranose, Carbocyclic analogs of hexopyranoses and pentofuranose, J. Org. Chem., 52 (1987) 1946-1956. 

Methyl 2Z,5-hexadienoate (126) undergoes cyclization to / S-parasorbic acid when treated with polyphosphoric acid. Torssell and his co-workers employed the substrate thus obtained for a new series of sugar synthesis. OL-Desosamine was synthesized in an essentially similar way to that described above. Analogously, DL-chalcose (127, 4,6-dideoxy-3-0-methyl-DL-xy/o-hexopyranose), was obtained, that is, by oxirane ring opening in racemic epoxy-lactone 122 with methanol in the presence of p-toluene-sulfonic acid. 

Lactone substrate 77 was obtained from 57 in one step in 90% yield and its C-4 epimeric analog was prepared by standard inversion procedure. Epoxidation was achieved by action of sodium hypochlorite in pyridine, while conversion to 3-azide required reduction of the epoxide with phenylse-leno(triisopropyloxy)borate, followed by treatment with diphenylphosphory-lazide under Mitsunobu reaction conditions [69]. The acetylated mixture of thioglycosides, obtained from 80, afforded good yield of the desired a-linked antibiotic upon reaction with daimomycinone. All four 2,6-dideoxy-3-azido-L-hexopyranoses were obtained from rhamnal via 4-epimeric lactones. 

Our laboratory (30) was the first to synthesize the (+)-enantiomer of levoglucosenone and its 5-hydroxymethyl analog, starting from the known precursor, 5-hydroxymethyl-l,6-anhydro-a-a//ro-hexopyranose as depicted in Scheme 9. 

All four diastereomeric 2-acetamido-2,4-dideoxy-D-hexopyranoses have been synthesized from the (5)-malic acid derived four-carbon aldehyde (37) (Scheme 11) as potential inhibitors of A/-acetylneuraminic acid synthase. The intermediates involved in the synthesis of the v-arabino-isomer (38) are shown in Scheme 11. The two vinyl Grignard addition reactions provided separable equimolar mixtures of C-3 epimers the analogous reactions applied to these yielded the three other isomeric amino-sugars. iV-Acyl-derivative (40) of L-daunosamine has been synthesized from the C-4-carboxy-branched intermediate (39), obtained by a stereoselective enolate-imine condensation (Scheme 12). The C-4-epimeric L-acosamine derivative was obtained by a similar sequence when compound (39) was first epimerized at C-4 (LiOH-HjO-MeOH). ... 

A number of -acyl- and thioureido-derivatives of 3 -amino-3 -deoxythymidine have been prepared. 1 0 Michael addition of phthalimide to enal (81) was used in the synthesis of the 3 -amino-2 ,3 -dideoxyhexo-furanose nucleosides (82) (all four isomers, R=H, Me, halogen),191 and a similar enal prepared by mercuric-ion catalysed hydrolysis of L-rhamnal was used in the same way to make the L-acosaminyl nucleoside (83) and its -anomer, and the L-ristosaminyl systems (epimers at C-3 ). 2 Michael addition of 1,2,4-triazole to (81) led, after base-sugar condensation, to the triazolyl-substituted nucleosides (84, B=T, U), together with the analogous hexopyranose systems. 93 xhe imidazolyl nucleosides (85) can be made by reaction of 3 -amino-3 -deoxythymidine with l,4-dinitroimidazoles, 9 whilst the unsaturated imidazole nucleoside (87) was made by treating the phenylselenone (86) (see Section 6) with imidazole. 195... 

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