Of octose derivatives

Several alkynes related to compound (29) were prepared by treatment of the corresponding dialdose derivative with alkynyl Grignard reagents, and by reduction and oxidation processes they were converted into a series of octose derivatives, e.g. reduction gave 7,8-dideoxy compounds and oxidation alkynyl glycos-6-uloses. ... 

S. Jeganaihan and P. Vogel, Highly stereoselective total syntheses of octoses and derivatives, J. Org. Chem. 56 1133 (1991) P. Vogel, D. Fattori.F. Gasparini, and C. Le Drian, Optically pure 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives ( naked sugars ) as new chirons, Synlett. p. 173 (1990). 

S. leganathan and P. Vogel, Highly stereoselective total syntheses of octoses and derivatives,... 

Catalytic osmylation of the allylic ethers and alcohols (12) led to the octose derivative (13) as the predominant isomer the Z) alkene (14.) gave the 7-epimer (15), in agreement with the empirical rule of Kishi that there will be an erythro-relationship between the oxygens at C-5 and C-6. The reaction sequence was also extended... 

Acyclic Alditols. - Brimacombe s group have published full details of their work on the stereoselective synthesis of higher sugars, some of which is covered in Chapter 2 other papers describe the Sharpless oxidation of the octose derivative (1) to give the oxiran (2), and hence the D-erythro isomer (3), osmylation... 

The C-vinyl unit (37) has been investigated as a component of the antibiotic aurodox and related compounds/ and the 2,6-anhydro-octose derivative (38), which is derived from the tetrahydropyranyl component of the antifungal agent ambruticin, has been made from L-arabinose by methods involving the use of methyl 3-nitropropanoate (Scheme 13), and thus its absolute stereochemistry is defined. 

Heptose and octose derivatives have been synthesized by way of nucleophilic C-alkylation of 1,2 3,4-di-0-isopropylidene-a-D-gfo/acro-1,5-hexodialdopyranose with the carbanions derived from 1,3-dithian and 2-methyl-1,3-dithian (Scheme 74) 330 -pjjg diastereoisomeric products could be formed in different proportions, depending on the solvent used. 

Further examples of four-carbon chain-extensions with 2-(trimethylsilyloxy)furan (see Vol.24, Chapter 2, Scheme 7) have been reported. Application of this method to 0-isopropylidene-D-glyceraldehyde afforded D-glycero-D-talo-hepxosc triacetonide (41), and an iterative procedure gave D-g/ycero-D-ra/o-L-to/o-undecanose pentaacetonide. Similarly, a 8-0-benzyl-L-r/irca-D-ra/o-octose derivative was obtained from 4-0-benzyl-2,3-0-isopropylidene-L-threose. ... 

Paulsen s group has reported the synthesis of derivatives (256) and (257) of the hydroxyethyl-branched octose that is found as a component of the quinocycline complexes isolated from Streptomyces aureofaciens. The route from the epoxyketone (255) is outlined in Scheme 59. An identical route was used to prepare branched-chain analogues in the o-series, in which it was shown that acid-catalysed methanolysis of the hydroxyethyl-branched derivative (258) yielded the more stable isomer (259) via the anhydro-sugar d-(257). Paulsen s group has also described a synthesis of a derivative (260) of pillarose (see Vol. 9, p. 99), a component of the antibiotic pillaromycin, using the dianion (261) prepared from 2-hydroxymethyl-l,3-dithiane to introduce the branch at C-4 (Scheme 60). A similar approach, using the anion derived from 2-methyl-l,3-dithiane, and subsequent desulphurization and reduction, etc., was adopted in a synthesis of a derivative (262) of aldgarose (4,6-dideoxy-3-C-[(i )-l-hydroxyethyl]-D-W6o-hexopyranose 3,3 -cyclic carbonate) (cf. Vol. 8, p. 100). 

Burgess et al. developed a novel approach for the synthesis of polyhydroxylated compounds such as castanospermine 87 and swainsonine 89 ° utilizing alkoxyallylboration of as one of the key steps (Eigure 25.12). Similarly, Jadhav and Woerner were able to convert the octose derivative 90 into the polyhydroxyindolizidine 91 in seven further transformations (Figure 25.12). Several of these indolizidines exhibit potent anti-cancer, anti-viral, and anti-AIDS activities. 

Phase 3. Formation activation and modification of a putative NDP-heptose. We suggest that the heptose moiety is derived from erfo-heptulose-7-phos-phate, which is the universal source for heptoses in all organisms having a functional pentosephosphate cycle. Also, for C-7 cyclitols (e.g., valien-amine) or for secondary metabolic sugar units with longer C chains, such as octoses (e.g., lincosamine, or the octose unit in APR, see Section 2.2.4.2), this seems to be the preferred precursor in actinomycete pathways. ... 

Treatment of the dichloromethyl derivative 472 with sodium cyanide gave290 an almost quantitative yield of the epimeric nitriles (480, 481). The mixture could not he separated by chromatographic methods, but differences in reactivity of the stereoisomers towards methanolic hydrogen chloride allowed isolation of only one ester, namely, 482 the trails cyanide underwent ready conversion into the methyl ester, whereas the cis compound gave a rather complicated mixture of products, with amide 483 being identified as the major component. Reduction of the ester group in 482, followed hydrolysis of the dichloromethyl group, afforded DL-t/ireo-DL- Y/o-octose, characterized as the heptaacetate, and identified as threo-ido-octito by comparison with an authentic sample. 

Octoses.1 A new route to octoses involves catalytic osmylation (7, 256-257) of allylic alcohols derived from a hexose by Wittig olefination to introduce two... 

The Synthesis of N-Acetyl-lincosamine (6-Acetamido-6,8-dideoxy-D-ert/fhro-D-ga-lacto-octose), a Derivative of the Free Carbohydrate Moiety in Lincomycin, G. B. Howarth, W. A. Szarek, and J. K. N. Jones, Chem. Commun., (1969) 1339-1340. 

The trivial names of the aldoses can be used as prefixes to determine the stereochemistry for other chiral compounds. However, in this case, the -ose suffix is omitted and the prefix is written in italics (Figure 2.8). In this respect, it should be mentioned that the chiral centers can be separated by one or more nonchiral centers. If the number of chiral centers exceeds four (e.g., in heptose, octose, nonose, etc. derivatives), a multiple configurational prefix is added to the stem name (Figure 2.9). In this case, the first four chiral centers are selected, followed by the remaining ones. However, the name of the compound starts with the prefix of the chiral center with the highest location. In the case of ketoses, if the carbonyl group is not at C-2, then its location should also be given in the name. 

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