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.