title: Prins cyclizations: labeling studies and application to natural product synthesis.
abstract: The first syntheses of two natural products, catechols 1 and 2, isolated from Plectranthus sylvestris (labiatae), are reported. Oxygen-18 labeling studies support the proposed intermediacy of a stabilized benzylic cation in the acid-promoted cyclization of an aldehyde and benzylic homoallylic alcohol possessing an electron-rich aromatic ring. In contrast, with an electron-deficient aromatic ring the pathway via a benzylic cation is only minor. [reaction: see text]
mesh_terms: D000893:Anti-Inflammatory Agents / Q000138:chemical synthesis; D000975:Antioxidants / Q000138:chemical synthesis; D001685:Biological Factors / Q000138:chemical synthesis*; D002396:Catechols / Q000138:chemical synthesis*; D003500:Cyclization; D019686:Lamiaceae / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000893:Anti-Inflammatory Agents; D000975:Antioxidants; D001685:Biological Factors; D002396:Catechols