Organocatalyzed C-C Ring Construction: The Mihovilovic Synthesis of Piperenol B
M. Kevin Brown of Indiana University prepared (J. Am. Chem. Soc. 2015, 137, 3482. ) the cyclobutane 3 by the organocatalyzed addition of 2 to the alkene 1. Karl Anker Jørgensen of Aarhus University assembled (J. Am. Chem. Soc. 2015, 137, 1685. ) the complex cyclobutane 7 by the addition of 5 to the acceptor 4, followed by condensation with the phosphorane 6.
Zhi Li of the National University of Singapore balanced (ACS Catal. 2015, 5, 51. ) three enzymes to effect enantioselective opening of the epoxide 8 followed by air oxidation to 9. Gang Zhao of the Shanghai Institute of Organic Chemistry and Zhong Li of the East China University of Science and Technology added (Org. Lett. 2015, 17, 688. ) 10 to 11 to give 12 in high ee. Akkattu T. Biju of the National Chemical Laboratory combined (Chem. Commun. 2015, 51, 9559. ) 13 with 14 to give the β-lactone 15. Paul Ha-Yeon Cheong of Oregon State University and Karl A. Scheidt of Northwestern University reported (Chem. Commun. 2015, 51, 2690. ) related results. Dieter Enders of RWTH Aachen University constructed (Chem. Eur. J. 2015, 21, 1004. ) the complex cyclopentane 20 by the controlled combination of 16, 17, and 18, followed by addition of the phosphorane 19.
Derek R. Boyd and Paul J. Stevenson of Queen’s University of Belfast showed (J. Org. Chem. 2015, 80, 3429. ) that the product from the microbial oxidation of 21 could be protected as the acetonide 22. Ignacio Carrera of the Universidad de la República described (Org. Lett. 2015, 17, 684. ) the related oxidation of benzyl azide (not illustrated). Manfred T. Reetz of the Max-Planck-Institut für Kohlenforschung and the Philipps-Universität Marburg found (Angew. Chem. Int. Ed. 2014, 53, 8659. ) that cytochrome P450 could oxidize the cyclohexane 23 to the cyclohexanol 24. F. Dean Toste of the University of California, Berkeley aminated (J. Am. Chem. Soc. 2015, 137, 3205. ) the ketone 25 with 26 to give 27. Benjamin List, also of the Max-Planck-Institut für Kohlenforschung, reported (Synlett 2015, 26, 1413. ) a parallel investigation. Philip Kraft of Givaudan Schweiz AG and Professor List added (Angew. Chem. Int. Ed. 2015, 54, 1960. ) 28 to 29 to give 30 in high ee.
Gloria Rassu of the Consiglio Nazionale delle Richerche and Franca Zanardi of the Università degli Studi di Parma combined (Angew. Chem. Int. Ed. 2015, 54, 7386. ) 31 and 32 to give the cyclohexadiene 33. Gregory C. Fu of the California Institute of Technology cyclized (J. Am. Chem. Soc. 2015, 137, 4587. ) the racemic allene 34 to the bicyclic diester 35 in high ee.
Marko D. Mihovilovic of the Vienna University of Technology effected (Eur. J. Org. Chem. 2015, 1464. ) microbial oxidation of sodium benzoate 36. The product was protected as the acetonide 37, that was carried over several steps to Piperenol B (38).