5. ANTIBIOSIS AND ANTIBIOTICS
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their macrolide moiety, they usually comprise one, two, or even three
[in the foromacidins or spiramycins from S. ambofaciens] unusual sugars
(XXII, XXV, XXVI, XXVIII, XXIX), of which one at least is an amino
sugar (XXI, XXIII, XXIV, XXVII). Lankamycin (272h), from S. viofoceoniger, is a conspicuous exception since it contains no nitrogen.
The complete structure of several macrolides has been established.
desosamine
(cxvn)
(cxvm)
c In methymycin: Ri = desosamine; R 2 = R3 = H; R 4 = OH
In neomethymycin: Ri = desosamine; R 2 = Rt = H; R 3 = OH
In picromycin: R 2 = desosamine; Ri = R 3 = H; R4 = OH
d In erythromycin A: Ri = cladinose; R 2 = OH.
In erythromycin Β: Ri = cladinose; R 2 = H.
In erythromycin C: Ri = unidentified sugar; R 2 = OH.