Protection of Organic Functional Groups

Amines can be activated for alkylation by N-formylation. Subsequent defoimylation of the alkylated formamide 11 has been a challenge. Longqin Hu of Rutgers University has developed (Tetrahedron Lett. 2007, 48, 4585) microwave conditions that work well. Carbamates are stable, but esters are not. Protection of amides can also be important. Michael J. Zacuto of Merck Process in Rahway, NJ has optimized (J. Org. Chem. 2007, 72, 6298) the Rh-catalyzed deaUylation of 13 to give 14. 

Carbonyl protection and deprotection is also important. Yoshihisa Kobayashi of the University of California, San Diego has devised (/. Org. Chem. 2007, 72, 3913) the isonitrile 15. Usually, the product 16 after Ugi condensation would he very difficult to hydrolyze. In the case of 16, mild acid effected cyclization to the acyl indole 17, which was easy to hydrolyze. In a different approach, Francesco Naso of the Universita di Bari has shown (Chem. Commun. 2007, 3756) that acid chlorides such as 18 condensed with 19 to give the furan 20. Such fiirans are easily oxidized, liberating the starting acid. 

---