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Monday, February 22, 2016
Douglass F. Taber
University of Delaware

Arrays of Stereogenic Centers: The Galano Synthesis of 16-B1-Phytoprostane

Masahiro Noji of the Meiji Pharmaceutical University described (J. Org. Chem. 2015, 80, 3203. ) an improved procedure for the iconic epoxidation of geraniol 1 to 2. John R. Falck of UT Southwestern Medical Center showed (Org. Lett. 2015, 17, 1058. ) that the selective epoxidation of the Z alkene of 3 delivered 4 in high ee.

Hisashi Yamamoto of Chubu University observed (J. Am. Chem. Soc. 2015, 137, 4308. ) high regioselectivity in the preparation of 6 by the Ni-mediated addition of aniline to the epoxide 5. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry devised (Angew. Chem. Int. Ed. 2015, 54, 5183. ) an organocatalyst that directed the addition of 8 to 7 to give the α-quaternary amine 9.

In another example of transfer hydrogenation, Michael J. Krische of the University of Texas prepared (J. Am. Chem. Soc. 2015, 137, 3161. ) 12 by adding the alkyne 11 to the alcohol 10. Tristan H. Lambert of Columbia University assembled (Chem. Sci. 2015, 6, 1537. ) 14 by enantioselective conjugate addition to 13. Chan-Mo Yu of Sungkyunkwan University prepared (Org. Lett. 2015, 17, 1573. ) the alkyne 17 by the 1,2-addition of the allenoate 16 to the aldehyde 15. Ken-ichi Takao of Keio University observed (Org. Lett. 2015, 17, 756. ) high diastereoselectivity in the addition of 19 to 18 to give 20.

Shu Kobayashi of the University of Tokyo used (J. Am. Chem. Soc. 2015, 137, 4336. ) a chiral crown ether to direct the addition of 22 to 21 to give 23. Yoshiaki Nishibayashi, also of the University of Tokyo, observed (Angew. Chem. Int. Ed. 2015, 54, 4060. ) that the aldehyde 26 could be prepared by coupling the eneamide 25 with 24.

X. Peter Zhang, now at Boston College, prepared (Chem. Sci. 2015, 6, 1219. ) the sulfone 28 by the cyclization of 27 followed by alkylation. Andrei V. Malkov of Loughborough University demonstrated (Chem. Eur. J. 2015, 21, 4551. ) that the acyclic oxy-Cope rearrangement of 29 led to 30 with good stereocontrol.

The phytoprostanes, represented by 16-B1-Phytoprostane (34), are naturally occurring oxidation products of α-linolenic acid. Jean-Marie Galano of the University of Montpellier took advantage (Front. Chem. 2015, 3, 41. ) of the previous observation by Hodgson (Org. Lett. 2005, 7, 2305. ) that the epoxide 31 was readily dimerized to 32 on exposure to LiTMP. Cross metathesis of 32 with 33 then led to 34.

D. F. Taber, Org. Chem. Highlights 2016, February 22.
URL: http://www.organic-chemistry.org/Highlights/2016/22February.shtm