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Monday, July 27, 2015
Douglass F. Taber
University of Delaware

Arrays of Stereogenic Centers: The Shin/Chandrasekhar Synthesis of (+)-Lactacystin

Kami L. Hull of the University of Illinois established (J. Am. Chem. Soc. 2014, 136, 11256. ) conditions for the diastereoselective hydroamination of 1 to 3. Jon C. Antilla of the University of South Florida employed (Org. Lett. 2014, 16, 5548. ) an enantiomerically-pure Li phosphate to direct the opening of the prochiral epoxide 4 to 5. Jordi Bujons and Pere Clapés of IQAC-CSIC engineered (Chem. Eur. J. 2014, 20, 12572. ) an enzyme that mediated the enantioselective addition of glycolaldehyde 7 to an aldehyde 6, leading to 8. Takahiro Nishimura of Kyoto University set (J. Am. Chem. Soc. 2014, 136, 9284. ) the two stereogenic centers of 11 by adding 10 to the diene 9.

Amir H. Hoveyda of Boston College added (J. Am. Chem. Soc. 2014, 136, 11304. ) the propargylic anion derived from 13 to the aldehyde 12 to give, after oxidation, the diol 14. Yujiro Hayashi of Tohoku University constructed (Adv. Synth. Catal. 2014, 356, 3106. ) 17 by the combination of 15 with 16. Yitzhak Apeloig and Ilan Marek of Technion-Israel Institute of Technology prepared (J. Org. Chem. 2014, 79, 12122. ) the bromo diol 20 by rearranging the adduct between the alkyne 19 and the acyl silane 18. James P. Morken, also of Boston College, effected (J. Am. Chem. Soc. 2014, 136, 17918. ) enantioselective coupling of 22 with the bis-borane 21. The product allyl borane added to benzaldehyde to give the alcohol 23.

Sentaro Okamoto of Kanagawa University reduced (Org. Lett. 2014, 16, 6278. ) the aryl oxetane 24 to an intermediate that coupled with allyl bromide to give the alcohol 25. In the presence of catalytic CuCN, the alternative diastereomer was the major product. Erick M. Carreira of ETH Zürich used (Angew. Chem. Int. Ed. 2014, 53, 13898. ) a combination of an Ir catalyst and an organocatalyst to couple the aldehyde 27 with the allylic alcohol 26. The four possible combinations of enantiomerically pure catalysts worked equally well, enabling the preparation of each of the four enantiomerically pure diastereomers of 28.

Jonathan W. Burton of the University of Oxford showed (Org. Lett. 2014, 16, 4078. ) that on oxidation, the α-amido malonate 29 cyclized to 30. Yong Jian Zhang of Shanghai Jiao Tong University assembled (Angew. Chem. Int. Ed. 2014, 53, 11257. ) the adjacent alkylated quaternary stereogenic centers of 33 by adding the carbonate 32 to 31. María D. Díaz-de-Villegas of the University of Zaragoza wrote (Adv. Synth. Catal. 2014, 356, 3261. ) a valuable review on the enantioselective α-functionalization of such 2-cyanoacetates.

Lactacystin (36) promotes neurite outgrowth. En route to a formal synthesis of 36, Dong-Soo Shin of Changwon National University and Srivari Chandrasekhar of the Indian Institute of Chemical Technology opened (Eur. J. Org. Chem. 2014, 6707. ) the epoxide 34 with azide, leading to 35.

D. F. Taber, Org. Chem. Highlights 2015, July 27.