Functional Group Protection: The Hudlicky Synthesis of Pleiogenone A
Using an iron catalyst, Hai Dong of the Huazhong University of Science and Technology observed (Chem. Eur. J. 2016, 22, 2481. DOI: 10.1002/chem.201504477) remarkable regioselectivity in the benzylation of 1 to 2. John D. Chisholm of Syracuse University devised (Org. Biomol. Chem. 2016, 14, 1623. DOI: 10.1039/C5OB02455B) 4 as a reagent for the direct conversion of an alcohol 3 to the ether 5. Keisuke Yoshida and Ken-ichi Takao of Keio University found (Tetrahedron Lett. 2016, 57, 627. DOI: 10.1016/j.tetlet.2015.12.114) that the N-oxide 7 was an effective catalyst for the TBDPS silylation of 6 to 8. Dean Markovíc of the University of Rijeka and Pierre Vogel of the Swiss Federal Institute of Technology and Maris Turks of Riga Technical University showed (Chem. Eur. J. 2016, 22, 4196. DOI: 10.1002/chem.201504380) that the reagent 10 was effective for the conversion of the sensitive aldol product 9 to 11.
Anikó Borbás and Pál Herczegh of the University of Debrecen deprotected (Org. Biomol. Chem. 2016, 14, 3190. DOI: 10.1039/C6OB00067C) 12 to 13 using catalytic BF3.OEt2. They showed that Cu(OTf)2 worked as well. Bernd Schmidt of the Universität Potsdam developed (Synthesis 2016, 48, 1399. DOI: 10.1055/s-0035-1561366) the direct thermal deprotection of 14 to 15.
Rama Krishna Peddinti of the Indian Institute of Technology Roorkee sulfonylated (Tetrahedron Lett. 2016, 57, 1232. DOI: 10.1016/j.tetlet.2016.02.009) 16 to 17 using the sulfonylhyrazide under oxidizing conditions. Sergey Miltsov of St. Petersburg State University selectively deprotected (Tetrahedron Lett. 2016, 57, 641. DOI: 10.1016/j.tetlet.2015.12.087) 18 to 19. Several other amine protecting groups were compatible with this procedure. David Milstein of the Weizmann Institute of Science hydrogenated (Chem. Commun. 2016, 52, 5285. DOI: 10.1039/C6CC01505K) the trifluoroacetamide 20 to the amine 21 and trifluoroethanol. Sentaro Okamoto of Kanagawa University deprotected (Tetrahedron Lett. 2016, 57, 2074. DOI: 10.1016/j.tetlet.2016.03.093) the propargyl carbamate 22 to the amine 23 under reducing conditions. Allyl carbamates were also deprotected.
Can-Cheng Guo of Hunan University used (Synthesis 2016, 48, 421. DOI: 10.1055/s-0035-1560967) DMSO as the methyl source for converting 24 to the ester 25. Bing Wang of Fudan University desilylated (Tetrahedron Lett. 2016, 57, 253. DOI: 10.1002/chem.201601061) 26 to the acid 27 with aqueous DMF.
In the course of the synthesis of pleiogenone A (30) (Chem. Eur. J. 2016, 22, 6180. DOI: 10.1002/chem.201601061), Tomas Hudlicky of Brock University needed to selectively hydrogenate 28 to 29. To this end, the enone was first protected by conjugate addition of thiophenol. Following the hydrogenation, the enone was regenerated by exposure to DBU.