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Monday, May 28, 2012
Douglass F. Taber
University of Delaware

Functional Group Protection

Zhong-Jun Li of Peking University developed (J. Org. Chem. 2011, 76, 9531. ) a Co catalyst for selectively replacing one benzyl protecting group of 1 with silyl. Carlo Unverzagt of Universitšt Bayreuth devised (Chem. Commun. 2011, 47, 10485. ) oxidative conditions for debenzylating the azide 3. Tadashi Katoh of Tohoku Pharmaceutical University found (Tetrahedron Lett. 2011, 52, 5395. ) that the dimethoxybenzyl protecting group of 5 could be selectively removed in the presence of benzyl and p-methoxybenzyl. Scott T. Phillips of Pennsylvania State University showed (J. Org. Chem. 2011, 76, 7352. ) that in the presence of phosphate buffer, catalytic fluoride was sufficient to desilylate 7. Philip L. Fuchs of Purdue University employed (J. Org. Chem. 2011, 76, 7834, not illustrated. ) the neutral Robins conditions (Tetrahedron Lett. 1992, 33, 1177. ) to effect a critical desilylation.

Pengfei Wang of the University of Alabama at Birmingham found (J. Org. Chem. 2011, 76, 8955. ) that an excess of the diol 9 both oxidized the primary alcohol 10, and installed the photolabile protecting group on the product aldehyde. Hiromichi Fujioka of Osaka University showed (Angew. Chem. Int. Ed. 2011, 50, 12232. ) that addition of Ph3P to 12 transiently protected the aldehyde, allowing selective reduction of the ketone to the alcohol.

Willi Bannwarth of Albert-Ludwigs-Universitšt Freiburg deprotected (Angew. Chem. Int. Ed. 2011, 50, 6175. ) the chelating amide of 14, leaving the usually sensitive Fmoc group in place. Bruce C. Gibb, now at Tulane University, hydrolyzed (Nature Chem. 2010, 2, 847. ) 16 more rapidly than the very similar 17, by selective equilibrating complexation of 16 and 17 with a cavitand.

Aravamudan S. Gopalan of New Mexico State University converted (Tetrahedron Lett. 2010, 51, 6737. ) proline 19 to the amide ester 10 by exposure to triethyl orthoacetate. K. Rajender Reddy of the Indian Institute of Chemical Technology oxidized (Angew. Chem. Int. Ed. 2011, 50, 11748. ) the formamide 22 to the carbamate 23 by exposure to H2O2 in the presence of 21. James M. Boncella of the Los Alamos National Laboratory deprotected (Org. Lett. 2011, 13, 6156. ) 24 by exposure to visible light in the presence of a Ru catalyst. David Milstein of the Weizmann Institute of Science employed (Angew. Chem. Int. Ed. 2011, 50, 11702, ; Nature Chem. 2011, 3, 609. ) a Ru catalyst to hydrogenate the urea 26 to the amine 27.

Satoshi Ichikawa and Akira Matsuda of Hokkaido University used (J. Org. Chem. 2011, 76, 9278. ) the acidity of the amide 29 to their advantage in effecting deprotection of 28. Akihiro Orita and Junzo Otera of the Okayama University of Science developed (Synlett. 2011, 2402. ) diphenylphosphoryl as a robust protecting group for a terminal alkyne such as 31.

D. F. Taber, Org. Chem. Highlights 2012, May 28.