Selective deprotection of phenacyl, benzyl and methyl esters of N-protected amino acids and dipeptides and N-protected amino acids benzyl ester linked to resins with bis(tributyltin) oxide

SALOMON, C.J.; MATA E.; MASCARETTI A.

JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1

Royal Society of Chemistry (Great Britain)

Año: 1996 vol. 10 p. 995 - 999

0300-922X

Phenacyl, methyl and benzyl esters of variousN-α-Boc, N-α-Cbz or N,N-dimethylamino protected amino acids and dipeptides, as well as esters of N-α-protected amino acids linked to Wang and Pam resins have been efficiently and chemoselectively cleaved by bis(tributyltin) oxide in aprotic solvents to give the corresponding carboxylic acids in good yields. Moreover, the absence of racemization during the deprotection has been demonstrated. A limitation of the method is the instability of the N-ε-Fmoc group in the amino acid esters 8 and 10, N-α-Fmoc-L-alanine linked to Wang resin 23 and the Cbz protecting groups in N-α-Boc-N-ε-Cbz-L-lysine benzyl and methyl esters (5 and 7), respectively, and N-α-Cbz-L-alanyl-L-alanine methyl ester 19. In the case of N-α-protected dipeptides, there was no evidence of free amino acid which indicates that the peptide bond is unaffected.