title: Tandem double-intramolecular [4+2]/[3+2] cycloadditions of nitroalkenes. Studies toward a total synthesis of daphnilactone B: piperidine ring construction.
abstract: [reaction: see text] Two model studies in support of a total synthesis of the complex polycyclic alkaloid daphnilactone B have been completed. The objectives of the models studies were to demonstrate the use of a tandem double-intramolecular [4+2]/[3+2] nitroalkene cycloaddition for the stereocontrolled construction of four of the rings in the core of the natural product. The first model study established the ability to create a pyrrolidine ring corresponding to ring A of daphnilactone B through a modification of the dipolarophile and subsequent functional group manipulations. The second model study required the modification of the dienophile in the [4+2] cycloaddition to accommodate the formation of a piperidine ring (ring B of daphnilactone B). Nitroalkene 26 containing a diene as the dienophile served well in the tandem cycloaddition to afford the nitroso acetal 38a in 77% yield. Subsequent functional group manipulations allowed for the high-yielding conversion to the core of daphnilactone B.
authors.affiliation: Department of Chemistry, Roger Adams Laboratory, University of Illinois, Urbana, Illinois 61801, USA. denmark@scs.uiuc.edu
authors.forename: Scott E
authors.initials: SE
authors.lastname: Denmark
authors.forename: Ramil Y
authors.initials: RY
authors.lastname: Baiazitov
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry*; D000475:Alkenes / Q000138:chemical synthesis* / Q000737:chemistry*; D007783:Lactones; D008958:Models, Molecular; D008968:Molecular Conformation; D010880:Piperidines / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D000470:Alkaloids; D000475:Alkenes; D007783:Lactones; D010880:Piperidines; C512154:daphnilactone B