1211543-89-3Relevant articles and documents
Selective triisopropylsilylation of α-amino acids: protection without racemization
Soto-Cairoli, Buddy,Kock, Iveliz,de Pomar, Jorge Justo,Yang, Guang,Guzman, Jose M.,Gonzalez, Javier R.,Antomattei, Augie,Soderquist, John A.
experimental part, p. 409 - 426 (2010/04/29)
The mono-, di- and trisilylation of α-amino acids with TIPSOTf is described. Treatment of the α-amino acids, proline and tryptophan with TIPSOTf in MeCN provides a quantitative yield of the corresponding ammonium salts of the O-TIPS esters (4). Employing two (2) equivalents of TIPSOTf/EDIPA produces N,O-bis-TIPS amino acid derivatives (2) without racemization as stable compounds (73-87%, 13 examples). Three (3) equivalents of this silylation mixture produces the corresponding tris-TIPS derivatives 6 (62-88%, 6 examples) from amino acids which contain protic functionality in their side chain. While this trisilylation procedure is ineffective for tryptophan, the N,O-bis-TIPS derivative 2m is easily prepared through this method, and the third silylation is achieved without racemization employing t-BuLi/R3SiX producing N1-SiR3-N,O-bis-TIPS tryptophans (51-97%, 4 examples).