Sixteen-membered ring macrolides

Carbomycin, Magnamycin. Sixteen -membered -ring macrolide antibiotic complex similar to leucomycin, q.v and erythromycin, q.v., produced by Streptomyces halstedil lsoln and antibacterial activity F. W. Tanner et al, Anti-... 

The complex sixteen-membered-ring macrolide antibiotic tylosin (191) is extensively used today as a therapeutic agent and a nutrient. The molecule has been at the focus of a number of synthetic investigations. This year, Nicolaou and co-workers have described the elaboration of the three fragments (186), (187), and (188) for the synthesis of 0-mycinosyltylonolide (190) in their appropriate optically active forms, and all three were formed from carbohydrate precursors. Combination between (186) and (187) gave rise to an intermediate which, with (188), was then elaborated to the keto-phosphonate (189). The... 

The naturally occuring avermectins are a family of eight, pentacyclic structures containing a sixteen-membered macrolide ring which are produced by Streptomyces avermitilis (Fig. 6) [60]. These eight compounds differ in structure due to the variability of PKS starter unit at C-25, the 0-methylation pattern at C-5, and the hydration-dehydration pattern at C-22/C-23. Other closely related natural products include the milbemycins and the nemadectins. The avermectins exhibit potent broad spectrum antiparasitic activity, and the semi-synthetic Ivermectin 29 (hydrogenated avermectin Bl) displays even greater efficacy [60,61]. 

Methods for the construction of large ring compounds and their application to macrolide synthesis continue to attract attention. The synthesis of pyrenophorin, a macrolide antibiotic, illustrates the effective use of protecting groups and functional group activation for construction of the sixteen-membered bis-lactone ring. ... 

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