title: Comprehensive study of okaspirodiol: characterization, total synthesis, and biosynthesis of a new metabolite from Streptomyces.
abstract: The new spiro[4.5]acetal okaspirodiol (4) was isolated from Streptomyces sp. Gö TS 19 as a secondary metabolite in yields up to 380 mg/L. The structure of this cryptic ketotetrol was elucidated by different methods including X-ray analysis, and its equilibration under mildly acidic conditions furnishing three additional isomers was thoroughly studied. Although metabolite 4 is not the thermodynamically favored isomer, a high-yielding total synthesis was accomplished comprising a stereoselective spiroacetalization under equilibrium conditions. This approach benefits from the important influence of an intramolecular hydrogen bond on the stabilization of the spiro[4.5]acetal moiety. The biosynthesis of 4 was investigated by feeding experiments with 13C-labeled precursors proving its origin from a new type of the rare mixed acetate-glycerol biosynthetic pathway. All results are discussed on the basis of the structural diversity of spiroacetals in nature and their chemical properties.
authors.affiliation: Institut für Organische und Biomolekulare Chemie and Institut für Anorganische Chemie der Georg-August-Universität Göttingen, Tammannstrasse 2-4, D-37077 Göttingen, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bender
authors.forename: Tim
authors.initials: T
authors.lastname: Schuhmann
authors.forename: Jörg
authors.initials: J
authors.lastname: Magull
authors.forename: Stephanie
authors.initials: S
authors.lastname: Grond
authors.forename: Paultheo
authors.initials: P
authors.lastname: von Zezschwitz
mesh_terms: D000080:Acetals / Q000138:chemical synthesis / Q000302:isolation & purification / Q000378:metabolism; D018360:Crystallography, X-Ray; D005285:Fermentation; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013141:Spiro Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013237:Stereoisomerism; D013302:Streptomyces / Q000378:metabolism*
chemical_list: D000080:Acetals; D013141:Spiro Compounds; C521601:okaspirodiol