Pentaene antibiotics

Macrolide pentaene antibiotic. Isol. from Streptomyces roseoflavus var. jenensis and S. maghwi. Antifungal agent with antiprotozoal props. Yellow-green cryst. (EtOH aq.). Mp 161-163°. [a]j - —45 (c. 1 in dioxan). Related to Dermostatin. 

C32H45NO9 587.709 Pentaene antibiotic. Prod, by Strepto-myces aureofaciens. Active against gram-positive organisms. Orange-red amorph. powder. Sol. MeOH, Et20, bases poorly sol. H2O,hexane. 

Actinomycin D, Antibiotic 205-2B, Blasticidin, Cycloheximide(actidione), Daunomycin DPB, Mithramycin, Mitomycin C, Pentaene G8, and Tubercidin. 

Upon heating with alkali most polyene antibiotics give a retroaldol reaction. Triggered by a ketonic carbonyl, characteristic aldehydes and/or ketones are formed. In the sixties and seventies this reaction was a valuable aid in the elucidation of the structure of polyene antibiotics. Natamy-cin, and all other polyenes mentioned in Figure 1, forms a pentaene aldehyde (from C13-C25), acetone (from C8-C10), and ethanal. Sofar the origin of the ethanal never has been elucidated clearly. While investigating tetrin A, Pandey et al. [11] used a variant of the above retroaldol reaction after acidification of the alkaline reaction mixture an additional amount of ethanal was formed. Pandey presumed that this additional amount was obtained from malonaldehydic acid, an intermediate formed upon heating with alkali (from C11-C12-C27). 

Pentamycin (molcidin B), isolated from the mycelium of Streptomyces pentaticus [68, 69] is a sugar-free pentaenic 28-membered lactone having the same constitution as fongichromin [70-72] (lagosin, cogomycin), and these two antibiotics were found to be identical after a detailed comparison of their peracetylated derivatives [66]. A very recent study of the stereostructure by Oishi et al. [66,67] defined the absolute configuration of the twelve asymmetric centers of this substance. 

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