Antibiotics branched-chain sugars from

The terms aminoglycoside as well as aminocyclitol antibiotic which are used for this class of natural products refer to the structural aspect. Most of the aminoglycoside antibiotics contain aminosugars and an aminocyclitol or a cyclitol moiety. The middle furanose part in streptomycin is called streptose and was the first branched-chain sugar obtained from microorganisms. The other rings in streptomycin are a IV-methyl-L-glucosamine moiety and an aminocyclitol called streptidine (O Fig. 20). 

Hydroformylation and deuterioformylation can also be applied to unsaturated carbohydrate derivatives142. Branched chain sugars (present in some antibiotics) are obtained as stereoiso-meric mixtures, mainly with low diastereoselectivities. From these results (using deuterated substrates) it was deduced for the first time that the oxo reaction proceeds via cis addition without direct involvement and epimerization of the asymmetric centers already present in the starting material142. 

The structure of nogalamycin, an antibiotic containing the branched-chain sugar nogalose, and that of o-hamamelose in solution are mentioned in Chapters 18 and 20, respectively. The preparation of an unusual trihalogenated, branched-chain heptulose (147) from xylaric acid has been discussed in Chapter 7. 

A new cytotoxic antibiotic cytorhodin X from a Streptomyces strain has been shown to be an unusual anthracyclinone 9a-glycoside 6. Another new anthracycline antibiotic, dutomycin, also obtained from a Streptomyces strain, contains a disaccharide component 7 including the branched chain sugar L-axenose. ... 

New paulomycin variants (35) have been isolated from S. paulus as minor components of the antibiotic complex they contain the same nucleus and sugars as do the major components A and B, but with differing acids esterifying the branched-chain sugar this sugar is... 

The 3, 5-iV-formylepimine derivative (432) [derived from the diacetal (431)] has been converted into a protected analogue (433) of the polyoxin antibiotics. The stereochemistry of the AT-formylepimine derivative (432) was established by A -ray crystallographic analysis. A series of lipophilic 9-(3-alkyl-3-deoxy-j8-D-ribofuranosyl)adenines (434) has been prepared by glycosylation of 6-benzamido-9-chloromercuripurine with the appropriate branched-chain sugar... 

Debono, M. and Molloy, R.M., Isolation and structure of the novel branched-chain amino sugar derived from antibiotic A35512B, J. Org. Chem., 45, 4685, 1980. 

D-Apiose can be isolated from parsley and is a component of the cell wall polysaccharide of various marine plants. Among its novel structural features is the presence of only a single chirality center. L-Vancosamine is but one portion of vancomycin, a powerful antibiotic that has emerged as one of only a few antibiotics that are effective against drug-resistant bacteria. L-Vancosamine is not only a branched-chain carbohydrate, it is a deoxy sugar and an amino sugar as well. 

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). 

Starting from the AT-Cbz-protected aldolase product 6, aza sugar 7 has been obtained stereoselectively by internal reductive amination as an analog of the bicyclic, indolizidine-type glycosidase inhibitor castanospermine [66]. Also, it had been recognized that the C12-C20 sequence of the macrolide antibiotic amphotericin B resembles the P-pyranose tautomer of 3 [76]. Thus, the branched-chain manno-configurated substrate 10 [77] was successfully chain-extended under NeuA catalysis to )deld the potential amphotericin B synthon 11 (Fig. 8) in good yield. 

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