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Journal/Book: Chemistry
Published: 2006
Pages: 2488–2503
Volume: 12
Accession no.: 114

Total synthesis and NMR investigations of cylindramide.

Nicolai Cramer, Maria Buchweitz, Sabine Laschat, Wolfgang Frey, Angelika Baro, Daniel Mathieu, Christian Richter, Harald Schwalbe
Cylindramide (1) was built up from three components: a hydroxyornithine derivative 7, a tetrazolylsulfone 8, and a substituted pentalene subunit 9. Derivative 7 was prepared in a six-step reaction sequence involving the Wittig reaction and a Sharpless asymmetric dihydroxylation starting from N-Boc-3-aminopropanal (12). Tetrazolylsulfone 8 was accessible in four steps from dioxinone 22. The synthesis of the pentalene fragment 9 started from cycloocta-1,5-diene 26, that was converted into enantiopure bicyclo[3.3.0]octanedione 29. The latter was functionalized to give derivative 9. The total synthesis was accomplished by inducing C-C bond formation by Sonogashira coupling of derivatives 9 and 7 followed by olefination with tetrazolylsulfone 8 under Julia-Kocienski conditions, macrocyclization, and subsequent Lacey-Dieckmann condensation to form the tetramic acid unit. As indicated by extensive 1H and 13C NMR spectroscopic investigations (DQF-COSY, ROESY spectra), the stereochemistry of synthetic cylindramide (1) corresponds with that of the naturally occurring product. ROE data were used for molecular modeling of the lowest-energy structures for cylindramide.
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Prof. Dr. Harald Schwalbe
Institut für Organische Chemie und Chemische Biologie
Johann Wolfgang Goethe Universität
Max-von-Laue-Str. 7
D-60438 Frankfurt am Main
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