Arrays of Stereogenic Centers: The Kobayashi/Kogen Synthesis of (-)-L-755,807
Yohei Shimizu and Motomu Kanai of the University of Tokyo showed (ACS Cent. Sci. 2016, 2, 21. ) that the allenyl borane 2 could be added to the unprotected sugar 1. Depending on the catalyst, either diastereomer of 3 could be prepared. Gui Lu of Sun Yat-sen University combined (Tetrahedron Lett. 2016, 57, 2554. ) 4, 5 and 6 to give 7. Arumugam Sudalai of the National Chemical Laboratory prepared (Tetrahedron Lett. 2016, 57, 2021. ) 10 by adding 8 to 6, then following up with 9. Shunying Liu and Wenhao Hu of East China Normal University assembled (Tetrahedron 2016, 72, 2929. ) 13 by combining 11, 12 and benzyl alcohol under Rh catalysis.
Yoshiharu Iwabuchi of Tohoku University achieved (Tetrahedron Lett. 2016, 57, 517. ) high regioselectivity in the opening of 14, prepared by directed epoxidation of the corresponding alkene, with the acetylide 15 to give 16. Yujiro Hayashi, also of Tohoku University, took advantage (Chem. Eur. J. 2016, 22, 3282. ) of the silyl tether of 17, cyclizing the derived dialdehyde, then combining that product with 18 to prepare the highly-functionalized 19. Ryan A. Shenvi of Scripps, La Jolla observed (Org. Lett. 2016, 18, 2620. ) high diastereoselectivity in the preparation of 21 by the free radical transfer of the phenyl group of 20 to the distal alkene. Andrew G. Myers of Harvard University easily scaled up (Angew. Chem. Int. Ed. 2016, 55, 523. ) the preparation of the crystalline nitro sugar 23 by simply exposing the alcohol 22 to glyoxal.
Stacey E. Brenner-Moyer of Rutgers University, Newark, effected (Org. Lett. 2016, 18, 2628. ) the γ-addition of the enone 25 to 24, leading to 26. Xiao-Mao Zhou of the Hunan Academy of Agricultural Sciences and Xiang-Ping Hu of the Dalian Institute of Chemical Physics established (Org. Lett. 2016, 18, 2734. ) the absolute configuration of 29 by adding 28 to racemic 27. Melodie Christensen and Andrew Nolting of Merck Process hydrogenated (J. Org. Chem. 2016, 81, 824. ) 30 to 31.
Intermolecular C-H insertion into simple alkanes can often lead to substantial mixtures. Nevertheless, Huw M. L. Davies of Emory University showed (Nature 2016, 533, 230. ) that insertion of 33 into n-octane 32 delivered 34 as the dominant product.
The epoxy-γ-lactam (-)-L-755,807 38, isolated by Merck scientists from the endophytic fungus Microsphaeropsis sp., is of potential interest as a promoter of neurite outgrowth. Kenichi Kobayashi and Hiroshi Kogen of Meiji Pharmaceutical University initiated (Org. Lett. 2016, 18, 1920. ) their synthesis of 38 by the diastereoselective Darzens addition of 36 to 35 to give 37. In the course of this work, the authors corrected the structure of 38 to that illustrated.