Organocatalyzed C-C Ring Construction: The Yoshida/Takao Synthesis of (-)-Misramine
Bor-Cherng Hong of the National Chung Cheng University assembled the cyclobutane 3 by adding 1 to 2 (Org. Lett. 2018, 20, 7835. ). Do Hyun Ryu of Sungkyunkwan University rearranged the initial cyclopropane from the addition of 5 to 4 to give the cyclobutanone 6 (J. Am. Chem. Soc. 2018, 140, 11184. ).
There are limited examples of transition-metal mediated carbonyl metathesis. Konrad Tiefenbacher of the University of Basel devised a supramolecular catalyst that facilitated the cyclization of the aryl ketone 7 to 8 (Angew. Chem. Int. Ed. 2018, 57, 14589. ). Mark S. Taylor of the University of Toronto developed conditions for the rearrangement of 9 to the cyclopentane 10 (Org. Lett. 2018, 20, 5327. ). David W. Lupton of Monash University designed a triazolylidene catalyst that cyclized 11 to 12 (Angew. Chem. Int. Ed. 2018, 57, 10299. ). Martin Oestreich of the Technische Universität Berlin showed that a boron Lewis acid could catalyze the enantioselective Nazarov reaction of 13 to 14 (Angew. Chem. Int. Ed. 2018, 57, 11441. ).
Benjamin List of the Max-Planck-Institut für Kohlenforschung used an enantiomerically-pure phosphoric acid to mediate the 1,6-addition of 15 to 16, leading to 17 (Angew. Chem. Int. Ed. 2018, 57, 10756. ). Hideki Abe and Hisanaka Ito of the Tokyo University of Pharmacy and Life Sciences used the Shi catalyst to convert the prochiral 18, readily prepared by alkylative Birch reduction of the corresponding benzoic acid, to the epoxide 19 (Chem. Commun. 2018, 54, 6165. ). Xianxing Jiang of Sun Yat-Sen University found that an enantiomerically-pure phosphine could direct the addition of 20 to 21, to give 22 (Org. Lett. 2018, 20, 4250. ). Łukasz Albrecht of the Lodz University of Technology used the Hayashi catalyst to assemble 25 by adding 24 to 23 (Chem. Eur. J. 2018, 24, 16543. ).
Paolo Melchiorre of ICIQ showed that a diamine catalyst could mediate the preparation of the cyclopentanone 28 by the conjugate addition of 27 to 26 (Nature Commun. 2018, 9, 3274. ). Makoto Fujita and Ikuro Abe of the University of Tokyo found a chimeric prenyltransferase-terpene synthase sequence in Penicillium chrysogenum MT-12, isolated from the Chinese club moss Huperzia serrata. Overexpressed in Aspergillus oryzae, this sequence combined 29 with 30 to generate a conformationally-mobile product, the structure of which was established to be 31 by crystalline sponge X-ray analysis (Org. Lett. 2018, 20, 5606. ).
Misramine (34), isolated from the above-ground portion of the Egyptian shrub Roemeria hybrida, is an oxidized proaporphine alkaloid. Keisuke Yoshida of Meijo University and Ken-ichi Takao of Keio University set the absolute configuration of 34 by cyclizing 32 to 33. The ee was improved to 94% by recrystallization at a later stage (Org. Lett. 2018, 20, 5044. ).