Streptomyces, branched-chain sugars from

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. ... 

Deoxy sugars showed an inhibitory effect on the biosynthesis of heparan sulphate [47], and a 4-deoxy branched-chain sugar is a structural feature of amipurimycin, isolated from Streptomyces novoguineensis, that presented a strong antifungal activity against Pyricularia oryzae [48],... 

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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