Maytansinoid ansa antibiotics

The maytansinoid ansa antibiotics are produced by Actinosynnema pre-tiosum (Actinomycetes), but also in a number of angiosperms, including Celasfraceae, Rhamnaceae and Euphorbiaceae. It has been suggested that the... 

Maytansine (73) was the first example of a benzenoid ansamycin with a Ci5 ansa chain. Maytansine was isolated originally from the higher plant Maytenus ovatus (Celastraceae). Subsequently, antibiotics related to maytansine were isolated from the fermentation broth of Nocardia sp. as well as other higher plants. Compounds belonging to the maytansinoid group possess a 1,3,5-trisubstituted benzene moiety as a chromophore. 

The ansamycin antibiotics represent a new class of natural products, combining an aromatic nucleus with a branching aliphatic side chain, and considerable interest has centered on their formation in nature. Their common structural features suggest immediately a similar biosynthetic pathway. Moreover, the streptovaricins, rifamycins, tolypo-micin B and halomicin B all have the same number of carbon atoms in the ansa ring (C17), while geldanamycin and the maytansinoids also have the same number of carbon atoms (C15). Thus far, biosynthetic... 

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