Carbon-Carbon Bond Formation: The Bergman Synthesis of (+)-Fuligocandin B
Xile Hu of the Ecole Polytechnique Fédérale de Lausanne optimized (J. Am. Chem. Soc. 2011, 133, 7084. ) a Ni catalyst for the coupling of a Grignard reagent 2 with a secondary alkyl halide 1. Duk Keun An of Kangwon National University devised (Tetrahedron Lett. 2011, 52, 1718, ; Chem. Commun. 2011, 47, 3281, ) a strategy for the reductive coupling of an ester 4 with a Grignard reagent 2 to give the secondary alcohol. Daniel J. Weix of the University of Rochester added (Org. Lett. 2011, 13, 2766. ) the halide 7 in a conjugate sense to the bromoenone 6, setting the stage for further organometallic coupling. James Y. Becker of the Ben-Gurion University of the Negev effected (J. Org. Chem. 2011, 76, 4710. ) Kolbe coupling of the silyl acid 9, to give the decarboxylated dimer 10.
Shi-Kai Tian of USTC Hefei showed (Chem. Commun. 2011, 47, 2158. ) that depending on the sulfonyl group used, the coupling of 11 with 12 could be directed cleanly toward either the Z or the E product. Yoichiro Kuninobu and Kazuhiko Takai of Okayama University added (Org. Lett. 2011, 13, 2959. ) the sulfonyl ketone 14 to the alkyne 13 to form the trisubstituted alkene 15. Jianbo Wang of Peking University assembled (Angew. Chem. Int. Ed. 2011, 50, 3510. ) the trisubstituted alkene 18 by adding the diazo ester 16 to the alkyne 17. Gangguo Zhu of Zhejiang Normal University constructed (J. Org. Chem. 2011, 76, 4071. ) the versatile tetrasubstituted alkene 21 by adding the chloroalkyne 19 to acrolein 20. Other more substituted acceptors worked as well.
Chunxiang Kuang of Tongji University and Qing Yang of Fudan University effected (Tetrahedron Lett. 2011, 52, 992. ) elimination of 22 to 23 by stirring with Cs2CO3 at 115°C in DMSO overnight. Toshiaki Murai of Gifu University created (Chem. Lett. 2011, 40, 70. ) a propargyl anion by condensing 24 with 25, then adding 26.
Xiaodong Shi of West Virginia University found (Org. Lett. 2011, 13, 2618. ) that the enantiomerically enriched propargyl ether 29 could be rearranged to the trisubsituted allene 30 with retention of the ee and with high de. Tsuyoshi Satoh of the Tokyo University of Science prepared (Tetrahedron Lett. 2011, 52, 3016. ) the trisubstituted allene 33 by the reduction of 31, itself readily available by the addition of a high ee dichlorosulfoxide to the unsaturated ester.
Jan Bergman of the Karolinska Institute observed (J. Org. Chem. 2011, 76, 1554. ) that condensation of 34 with 35 led directly to 36, by episulfide formation and extrusion. The vinylogous amide 36 was readily epimerized with base, but could be deprotected using the Fukuyama protocol with maintenance of enantiomeric excess.