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Monday, February 23, 2015
Douglass F. Taber
University of Delaware

Arrays of Stereogenic Centers: The Thomson Synthesis of (-)-Galcatin

Hisashi Yamamoto of the University of Chicago and Chubu University developed (J. Am. Chem. Soc. 2014, 136, 1222. ) a tungsten catalyst for the enantioselective oxidation of allyic alcohols such as 1 to the epoxide 2. Homoallylic alcohols also worked well. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry devised (Chem. Eur. J. 2014, 20, 68. ) a scalable Zn-catalyzed protocol for the coupling of 3 with 4 to give 5. Professor Shibasaki and Takumi Watanabe, also of the Institute of Microbial Chemistry, established (Org. Lett. 2014, 16, 3364. ) a Nb catalyst for the preparation of 8 by the Henry addition of 7 to 6. Wenhao Hu of East China Normal University effected (Synthesis 2014, 46, 1348. ) the coupling of 9 and 10 with two equivalents of aniline to give the diamine 10.

Sanzhong Luo of the Institute of Chemistry, Beijing showed (Angew. Chem. Int. Ed. 2014, 53, 4149. ) that the adduct between 11 and an in situ-formed N-nitroso could be reduced with high diastereoselectivity, leading to 12. Kumagai and Shibasaki also described (Angew. Chem. Int. Ed. 2014, 53, 5327. ) the assembly of 15 by the enantioselective addition 14 to 13. Bernhard Breit of the Albert-Ludwigs-Universität Freiburg effected (Synthesis 2014, 46, 1311. ) the carbonylation of the alkene 16 to give an aldehyde that underwent in situ condensation with the imine 17, leading, after a subsequent addition of vinyl magnesium chloride, to the lactone 18. Michael J. Krische of the University of Texas prepared (J. Am. Chem. Soc. 2014, 136, 8911. ) the diol 21 by adding the racemic epoxide 20 to the aldehyde 19.

Martin Hiersemann of the Technische Universität Dortmund achieved (J. Org. Chem. 2014, 79, 3040. ) high enantioselectivity in the rearrangement of the enol ether 22 to 23. Michael T. Crimmins also observed (Org. Lett. 2014, 16, 2458. ) high stereocontrol in the rearrangement of 24 to 25. Wannian Zhang and Chunquan Sheng of the Second Military Medical University and Wei Wang of the University of New Mexico and the East China University of Science and Technology added (Org. Lett. 2014, 16, 692. ) the diketone 26 to the aldehyde 6 to give an intermediate adduct, that further cyclized to 27. Helma Wennemers of ETH Zürich used (J. Org. Chem. 2014, 79, 3937. ) an organocatalyst to effect the coupling of 28 with 29 to give 30 in high ee.

The nutmeg Pycanthus angolensis and the pepper plant Holostylis reniformis have traditionally been used, in Africa and Brazil respectively, to treat malaria. Tetralin lignans isolated from these sources have been shown to have significant antiplasmodial activity. Regan J. Thomson of Northwestern University devised (Angew. Chem. Int. Ed. 2014, 53, 1395. ) a general strategy for the preparation of this class of natural products, based on the oxidative rearrangement of a hydrazone such as 31. The intermediate carbocation from the rearrangement coupled with 32 to give 33 with remarkable stereocontrol. The product 33 was readily carried on to (-)-Galactin (34).

D. F. Taber, Org. Chem. Highlights 2015, February 23.
URL: https://www.organic-chemistry.org/Highlights/2015/23February.shtm