title: Mechanistic and computational studies of exocyclic stereocontrol in the synthesis of bryostatin-like cis-2,6-disubstituted 4-alkylidenetetrahydropyrans by Prins cyclization.
abstract: The Prins cyclization of syn-β-hydroxy allylsilanes and aldehydes gives cis-2,6-disubstituted 4-alkylidenetetrahydropyrans as sole products in excellent yields regardless of the aldehyde (R″) or syn-β-hydroxy allylsilane substituent (R') used. By reversing the R″ and R' groups, complementary exocyclic stereocontrol can be achieved. When the anti-β-hydroxy allylsilanes are used, the Prins cyclization gives predominantly cis-2,6-disubstituted 4-alkylidenetetrahydropyrans, now with the opposite olefin geometry in excellent yield. The proposed reaction mechanism and the observed stereoselectivity for these processes are supported by DFT calculations.
authors.affiliation: Department of Chemistry, University of California, Davis, California 95616, United States.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Phillip P
authors.initials: PP
authors.lastname: Painter
authors.forename: Dean J
authors.initials: DJ
authors.lastname: Tantillo
authors.forename: Paul A
authors.initials: PA
authors.lastname: Wender
mesh_terms: D000475:Alkenes / Q000138:chemical synthesis* / Q000737:chemistry; D054713:Bryostatins / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D015394:Molecular Structure; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000475:Alkenes; D054713:Bryostatins; D011714:Pyrans; C046785:bryostatin 1