title: ent-Kaurane-based regio- and stereoselective inverse electron demand hetero-Diels-Alder reactions: synthesis of dihydropyran-fused diterpenoids.
abstract: A mild and concise approach for the construction of a 3,4-dihydro-2H-pyran ring integrated into the A-ring of the natural product oridonin using an optimized inverse electron demand hetero-Diels-Alder (IED HDA) reaction is reported herein. A self-dimerization of the exocyclic enone installed in the A-ring through a homo-HDA reaction was identified to exclusively give a dimeric ent-kaurane diterpenoid with the spirochroman core. Moreover, efficient cross-HDA cycloadditions of this enone with various vinyl ethers or vinyl sulfides, instead of its own homo-HDA dimerization, were achieved in a regio- and stereoselective manner, thus providing access to novel dihydropyran-fused diterpenoids as potential anticancer agents to overcome chemoresistance.
authors.affiliation: Chemical Biology Program, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555, USA. jizhou@utmb.edu.
authors.forename: Chunyong
authors.initials: C
authors.lastname: Ding
authors.forename: Lili
authors.initials: L
authors.lastname: Wang
authors.forename: Haijun
authors.initials: H
authors.lastname: Chen
authors.forename: Christopher
authors.initials: C
authors.lastname: Wild
authors.forename: Na
authors.initials: N
authors.lastname: Ye
authors.forename: Ye
authors.initials: Y
authors.lastname: Ding
authors.forename: Tianzhi
authors.initials: T
authors.lastname: Wang
authors.forename: Mark A
authors.initials: MA
authors.lastname: White
authors.forename: Qiang
authors.initials: Q
authors.lastname: Shen
authors.forename: Jia
authors.initials: J
authors.lastname: Zhou
mesh_terms: D001688:Biological Products / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D061565:Cycloaddition Reaction; D019281:Dimerization; D045786:Diterpenes, Kaurane / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D001688:Biological Products; D045786:Diterpenes, Kaurane; D011714:Pyrans; C011959:oridonin