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Monday, September 14, 2009
Douglass F. Taber
University of Delaware

Practical Enantioselective Construction of Arrays of Stereogenic Centers: The J°rgensen Synthesis of the Autoregulator IM-2

Amando Cˇrdova of Stockholm University found (Angew. Chem. Int. Ed. 2008, 47, 8468. ) that the enantiomerically-enriched diastereomers from aminosulfenylation of 1 were readily separable by silica gel chromatography. Benjamin List of the Max-Planck-Institut, MŘlheim developed (Angew. Chem. Int. Ed. 2008, 47, 8112. ) what appears to be a general protocol for the enantioselective epoxidation of enones such as 4. Paolo Melchiorre of the UniversitÓ di Bologna devised (Angew. Chem. Int. Ed. 2008, 47, 8703. ) a related protocol for the enantioselective aziridination of enones. Xue-Long Hue of the Shanghai Institute of Organic Chemistry and Yun-Dong Wu of the Hong Kong University of Science and Technology optimized (J. Am. Chem. Soc. 2008, 130, 14362. ) a Cu catalyst for enantioselective Mannich homologation of imines such as 6. Guofu Zhong of Nanyang Technological University, Singapore established (Angew. Chem. Int. Ed. 2008, 47, 10187, ; Org. Lett. 2008, 10, 4585, ) that enantioselective α-aminoxylation of an ω-alkenyl aldehyde such as 9 could lead to defined arrays of stereogenic centers.

George A. O'Doherty of West Virginia University devised (Org. Lett. 2008, 10, 3149. ) a protocol for the enantioselective hydration of 12 to 13. RenÚ Peters of the University of Stuttgart designed (Angew. Chem. Int. Ed. 2008, 47, 5461. ) an Al catalyst for the enantioselective combination of an acyl bromide 15 with an aldehyde14 to deliver the β-lactone 16. Hajime Ito and Masaya Sawamura of Hokkaido University established (J. Am. Chem. Soc. 2008, 130, 15774. ) that the allenyl borane from 17 added to aldehydes such as 18 with high ee. Keiji Maruoka of Kyoto University developed (Tetrahedron Lett. 2008, 49, 5369. ) an organocatalyst for the Mannich homologation of an aldehyde such as 20 to 21.

R. Karl Dieter of Clemson University showed (Org. Lett. 2008, 10, 2087. ) that 23,readily prepared in high ee, could be displaced sequentially with two different Grignard reagents, to give 24. Jeffrey W. Bode, now at the University of Pennsylvania, found (Org. Lett. 2008, 10, 3817. ) that bisulfite adducts such as 25 served well for the addition of unstable chloroaldehydes to 26 to give 27. Sunggak Kim of KAIST, Daejeon observed (Org. Lett. 2008, 10, 3149. ) that the radical addition of 29 to 28 with allylation of the intermediate radical delivered 30 with high diastereocontrol. Peter A. Jacobi of Dartmouth College prepared (Org. Lett. 2008, 10, 2837. ) the ester 31 by enantioselective reduction of the enone. Claisen rearrangement followed by TBAF elimination gave 32.

Karl Anker J°rgensen of Aarhus University, Denmark used (Chem. Commun. 2008, 5827. ) a Chincona based catalyst to effect enantioselective addition of 33 to 34. Enantioselective reduction of the ketone 35 to the alcohol followed by conversion of the nitro group to the alcohol led to IM-2 (36), an autoregulator derived from Streptomyces.

It is a measure of the progress that has been made in this area that fifteen years ago, developing a route to a family of drug products that contained two adjacent ternary alkylated stereogenic centers was a significant challenge for the process group of a major pharmaceutical company.

D. F. Taber, Org. Chem. Highlights 2009, September 14.