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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Oxidative Carbon Backbone Rearrangement in Rishirilide Biosynthesis.
Olga Tsypik1, Roman Makitrynskyy1, Britta Frensch2
1Department of Pharmaceutical Biology and Biotechnology, Institute of Pharmaceutical Sciences, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Straße 19, 79104 Freiburg, Germany.
This study reveals how Streptomyces bottropensis enzymes RslO5, RslO9, and RslO8 rearrange polyketide precursors. These redox tailoring steps generate complex molecules like rishirilides and lupinacidin A.
Area of Science:
- Biochemistry
- Natural Product Biosynthesis
- Enzymology
Background:
- Type II polyketides exhibit significant structural diversity due to tailoring enzymes.
- Previous 13C-labeling studies suggested complex rearrangements in rishirilide biosynthesis by Streptomyces bottropensis.
Purpose of the Study:
- To identify key biosynthetic intermediates in rishirilide and lupinacidin A formation.
- To elucidate the intricate redox tailoring steps involved in the biosynthesis of rishirilides A, B, and D, and lupinacidin A.
Main Methods:
- Gene deletion experiments in Streptomyces bottropensis.
- In vitro enzymatic studies of isolated tailoring enzymes.
- Characterization of biosynthetic intermediates.
Main Results:
- The flavin-dependent RslO5 reductively ring-opens an epoxide intermediate.
- Flavin monooxygenase RslO9 performs oxidative carbon backbone rearrangement via Baeyer-Villiger oxidation and aldol condensation.
- Ketoreductase RslO8 is essential for forming rishirilides A and B, while RslO9 produces rishirilide D and lupinacidin A.
Conclusions:
- Unusual redox tailoring reactions, including Baeyer-Villiger oxidation and aldol condensation, drive structural diversification of polyketides.
- The identified enzymes and pathways provide insight into the biosynthesis of complex aromatic polyketide natural products.
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