Total synthesis of tropoloisoquinolines: imerubrine, isoimerubrine, and grandirubrine.
A unified, ready access to the tropoloisoquinoline alkaloids imerubrine (1), grandirubrine (2), and isoimerubrine (3) is delineated and features sequential application of the intramolecular Diels-Alder reaction of an acetylene-tethered oxazole and the [4 + 3] cycloaddition of an oxyallyl. A regioselective synthesis of 1 was achieved by stereo- and regioselective oxidation of an 8-oxabicyclo[3.2.1]oct-6-en-3-one cycloadduct by means of the Moriarty method. Such a post-cycloaddition functionalization complements the synthetic utility of an alpha-alkoxy-substituted oxyallyl so as to broaden the scope of the oxyallyl [4 + 3] cycloaddition reaction.
Lee
J C
JC
Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
Cha
J K
JK
D000470:Alkaloids / Q000138:chemical synthesis; D007546:Isoquinolines / Q000138:chemical synthesis*; D010946:Plants, Medicinal / Q000737:chemistry; D013237:Stereoisomerism; D014334:Tropolone / Q000031:analogs & derivatives / Q000138:chemical synthesis*
D000470:Alkaloids; D007546:Isoquinolines; C434338:grandirubrine; C434339:isoimerubrine; C043049:imerubrine; D014334:Tropolone