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Total synthesis of neomethymycin and novamethymycin has been achieved. These two macrolides contains 12-membered macrolactones as aglycones and belong to the methymycin family of antibiotics, which appears in the pikromycin biosynthetic pathway. The segments in the 12-membered macrolactone that are responsible for causing structural difference in neomethymycin and novamethymycin were synthesized by starting with methyl d -(+)-lactate and d -glucose, for neomethynolide, and for novamethynolide, respectively. The key steps in synthesis of neomethynolide and novamethynolide, which are aglycones for neomethymycin and novamethymycin, respectively, were asymmetric aldol reactions, Yamaguchi esterification, and ring-closing metathesis using Grubbs’ second generation catalyst. Finally, the coupling of agylcones with the corresponding trichloroacetimidates, followed by deprotection, completed the total synthesis of these two macrolide antibiotics. |
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