Helvolic acid structure

The structure of helvolic acid has been revised to (13). The ring b acetoxy-group is at C-6 and not at C-7 as was previously suggested. As a result, a similar modification must be made to the structures of helvolinic acid, 7-deacetoxyhelvolic acid, and 7-oxofusidic acid. The two interesting double bond isomers (14) and... 

Further details have been published relating to the structure of cephalosporin P, and the structure of the related helvolic acid has been revised to the 6j6-acetoxy-7-ketone (519). 

Steroid Antibiotics. The steroid antibiotics are a structurally diverse class of steroids that have a common biological function, ie, antibacterial, antifungal, antiviral, or antitumor activities. This group of compounds can overlap with other steroid classes listed above. Fusidic acid [6990-06-3] (67), helvolic acid [29400 42-8] (68), and cephalosporin [13258-72-5] (69) exemplify a set of antibacterial steroids that contain a prolanostane skeleton with an... 

Protostane and their 29-nor-derivatives denoted as fusidanes are fimgal metabolites. Cephalosporium caerulens, for instance, produces (-l-)-protosta-17(20)-( -24-diene-3p-ol. Fusidanes sueh as helvolic acid from the Helvola mutant of the mold Aspergillus fumigatus and related structures are widely used as antibacterials. Fusi-dic acid isolated from the fermentation broth of Fusidium coccineum and related tribes is an example. Its sodium salt has immunosuppressive and antibacterial properties, and is applied in ointments against multiresistant staphylococci during the therapy of wound infections... 

The structurally related cephalosporin and helvolic acid do not appear to have the same antibacterial potency as fusidic acid [271, 336, 337] and so would not seem destined for equivalent status in medicine. Similarly the antibacterial potency of the triterpenoid antibiotics polyporenic acid A [338] and polyporenic acid C [339], like that [340] of pristimerin (LXI) [341, 342], which is one of the most highly oxidised naturally occurring pentacyclic triterpenes... 

It remains to be seen, however, whether these latter compounds or structural modifications of them will find application chnically. Certainly any earher hopes for useful therapeutic application of the triterpenoid cucurbitacins as founded on the high order of their cytotoxicity in vitro [479-484] have been dashed on account of the very low margins between the active and the toxic doses as revealed in in vivo experiments. Since the earlier review was written the structures of the cucurbitacins have been elucidated in full and they have been found to represent an unusual structural type in which backbone rearrangement in the formal carbonium ion initially formed from the cychsation of squalene epoxide in chair-boat-chair-boat conformational sequence proceeds beyond the stages giving rise to lanosterol and cycloartenol. Thus they can be regarded as overshoots of the biosynthetic pathway giving rise to the steroids in the same way as fusidic acid (LX), cephalosporin and helvolic acid represent undershoots of the same pathway. The structure of cucurbitacin A is as depicted in LXIV [485, 486]. 

Antibiotics - The conplete structure V for Helvolic acid has been proposed, based on chemical evidence. ... 

Helvolic acid, C33H44O8, probably has structure I, although this must be regarded as tentative (Okuda et al., 1964). 

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