Functional Group Transformation: The Castle Synthesis of Celogentin C

Mark Cushman of Purdue University found (J. Org. Chem. 2010, 75, 3507) that a benzylic methyl ether 1 could be converted to the aldehyde 2 by N -bromosuccinimide. Two equivalents of NBS gave the methyl ester. Ning Jiao of Peking University used (Organic Lett. 2010, 12, 2888) NaN3 followed by DDQ to oxidize a benzylic halide 3 to the nitrile 4. Hugues Miel of Almac Sciences oxidized (Tetrahedron Lett. 2010, 51, 3216) the ketone 5 to the nitro derivative 6. The oxidative conversion of the nitro compound 7 to the ketone 8 described (Tetrahedron Lett. 2009, 50, 6389) by Vera L. Patrocinio Pereira of the Universidade Federal do Rio de Janeiro proceeded without epimerization. Sundarababu Baskaran of the Indian Institute of Technology Madras established (Angew. Chem. Int. Ed. 2010, 49, 804) that oxidative cleavage of the benzylidene acetal 9 delivered 10 with high regioselectivity. The intramolecular alkene dihydroxylation of 11 originated (Angew. Chem. Int. Ed. 2010, 49, 4491) by Erik J. Alexanian of the University of North Carolina gave 12 with high diastereocontrol. Ruimao Hua of Tsinghua University took advantage (J. Org. Chem. 2010, 75, 2966) of the H-donor properties of DMF to develop an efficient reduction of the alkyne 13 to the alkyne 14 . Alejandro F. Barrero of the University of Granada developed (J. Am. Chem. Soc. 2010, 132, 254) Ti (III) conditions for the reduction of the allylic alcohol 15 to the terminal alkene 16. Isolated alkenes were stable to these conditions. P. Veeraraghavan Ramachandran, also of Purdue University, effected (Tetrahedron Lett. 2010, 51, 3167) reductive amination of 17 to 18 using the now readily available NH3 - BH3 . Bin Ma and Wen-Cherng Lee of BiogenIdec developed (Tetrahedron Lett. 2010, 51, 385) a simple protocol for the conversion of an acid 19 to the free amine 20. Marc Lemaire of Université Lyons 1 established (Tetrahedron Lett. 2010, 51, 2092) that the silane 22 reduced primary, secondary, and tertiary amides to the aldehydes.

C-H Functionalization: The Chen Synthesis of Celogentin C

Christian R. Goldsmith of Auburn University developed (Synlett 2010, 1377) a method for radical chlorination of 1 using commercial peracetic acid. Noritaka Mizuno of the University of Tokyo devised (Nat. Chem. 2010, 2, 478) a bulky polyoxometalate that mediated the selective hydroxylation of the secondary C-H bonds of 3. Christina White of the University of Illinois showed (Science 2010, 327, 566) that Fe-mediated C-H oxidation is sensitive to the expected electronic effects, so that 5 was selectively oxidized to 6. Irena S. Akhrem of the A. N. Nesmeyanov Institute of Organoelement Compounds established (Tetrahedron Lett. 2010, 51, 259) that a C-H bond of 7 could be efficiently converted to a C-C bond. Melanie S. Sanford of the University of Michigan extended (Organic Lett. 2010, 12, 532) directed palladation to 9, effecting selective acetoxylation of the methyl group. Herman O. Sintim of the University of Maryland observed (Angew. Chem. Int. Ed. 2010, 49, 3964) that the O-linked diazoamide 11 selectively cyclized to 12. The corresponding C-linked diazoamide gave only five-membered ring formation. Yasushi Obora and Yasutaka Ishii of Kansai University devised (Organic Lett. 2010, 12, 1372) conditions for the selective allylic amination of 13. Marvin J. Miller of the University of Notre Dame developed (Tetrahedron Lett. 2010, 51, 328) the nitrosoisoxazole 16 for the allylic amination of 15. David A. Powell of Merck Frosst established (J. Org. Chem. 2010, 75, 2726) a protocol for the selective amination of the aromatic methyl group of 18. Ying-Yeung Yeung of the National University of Singapore effected (Organic Lett. 2010, 12, 2128) selective allylic oxidation of 21 with a hypervalent iodine reagent. Gullapalli Kumaraswamy of the Indian Institute of Chemical Technology, Hyderabad, allylated (J. Org. Chem. 2010, 75, 3916) an amine 23 using commercial aqueous t -BuOOH. Corey R. J. Stephenson of Boston University used (J. Am. Chem. Soc. 2010, 132, 1464) visible light to activate 26 for homologation to 27. In the course of a synthesis of the bicyclic nonribosomal peptide celogentin C, isolated from the seeds of the plumed cockscomb Celosia argentea, Gong Chen of Pennsylvania State University took advantage (Angew. Chem. Int. Ed. 2010, 49, 958) of Pd activation to effect specific coupling of the iodoindole 29 with the leucine derivative 28. On a 4-gram scale, this coupling proceeded in 85% yield.