- Chemoenzymatic Total Synthesis and Structural Diversification of Tylactone-Based Macrolide Antibiotics through Late-Stage Polyketide Assembly, Tailoring, and C-H Functionalization
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Polyketide synthases (PKSs) represent a powerful catalytic platform capable of effecting multiple carbon-carbon bond forming reactions and oxidation state adjustments. We explored the functionality of two terminal PKS modules that produce the 16-membered tylosin macrocycle, using them as biocatalysts in the chemoenzymatic synthesis of tylactone and its subsequent elaboration to complete the first total synthesis of the juvenimicin, M-4365, and rosamicin classes of macrolide antibiotics via late-stage diversification. Synthetic chemistry was employed to generate the tylactone hexaketide chain elongation intermediate that was accepted by the juvenimicin (Juv) ketosynthase of the penultimate JuvEIV PKS module. The hexaketide is processed through two complete modules (JuvEIV and JuvEV) in vitro, which catalyze elongation and functionalization of two ketide units followed by cyclization of the resulting octaketide into tylactone. After macrolactonization, a combination of in vivo glycosylation, selective in vitro cytochrome P450-mediated oxidation, and chemical oxidation was used to complete the scalable construction of a series of macrolide natural products in as few as 15 linear steps (21 total) with an overall yield of 4.6%.
- Lowell, Andrew N.,Demars, Matthew D.,Slocum, Samuel T.,Yu, Fengan,Anand, Krithika,Chemler, Joseph A.,Korakavi, Nisha,Priessnitz, Jennifer K.,Park, Sung Ryeol,Koch, Aaron A.,Schultz, Pamela J.,Sherman, David H.
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p. 7913 - 7920
(2017/06/20)
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- Semisynthetic Macrolide Antibacterials Derived from Tylosin. Synthesis of 3-O-Acetyl-23-O-demycinosyl-4''-O-isovaleryltylosin and Related Compounds, as well as the 12,13-Epoxy Derivatives
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Selective acylation techniques have been developed that enable the synthesis of 3-O-acetyl-4''-O-isovaleryltylosin and 3-O-acetyl-23-O-demycinosyl-4''-O-isovaleryltylosin to be carried out in an efficient manner starting from tylosin.The syntheses of the 2'-O-acetyl, 23-O-acetyl, and 2',23-di-O-acetyl derivatives of the latter are also described.The synthesis of key hydrazones is also described.The regio- and stereo-selective epoxidation of tylosin and its acyl derivatives afforded the 12,13-epoxyanalogues, which were used to synthesize novel acylated 12,13-epoxy derivatives of 23-O-demycinosyltylosin.
- Fishman, Andrew G.,Mallams, Alan K.,Rossman, Randall R.
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p. 787 - 798
(2007/10/02)
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