Octose derivatives synthesis

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... 

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. 

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 presented review describes total syntheses directed towards 6-amino-6,8-dideoxy-D-eryt/iro-D-galacto-octose, commonly named lincosamine - the sugar component of the antibiotic lincomycin. In the first part we present total syntheses of lincosamine that start from carbohydrate precursors. The D-galactose-derived aldehyde is the most frequently used synthon. In the second part, total syntheses of lincosamine from non-carbohydrate precursors are presented. This part of the review is divided into two subsections. The first one groups syntheses based on the application of furan compounds. In the second one we present a hetero-Diels-Alder approach to the synthesis of lincosamine. 

The synthesis of sugars by iterative, diastereoselective homologation of aldehydo-sugars with 2-trimethylsilylthiazole mentioned last year (see Vol. 19 p 5 ref. 11) has been extended up to nonose derivatives. The newly created chiral centre at C-2 invariably bore an erythro relationship to the C-3 substituent thus, D-glyceraldehyde led to the D-allose derivative (19)f and the meso-octitol (20) was obtained via the corresponding octose. 

A review lecture including the synthesis of branched-chain sugars using the dithiane route and glycoside synthesis with branched-chain sugars has been published and full reports on the synthesis of the y-octose obtained from isoquinocycline A and of related 4-C-hydroxyethylhexose derivatives have now appeared (see Vol. 10, p. 98). 

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). 

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