An efficient method for the synthesis of phenacyl ester-protected dipeptides using neutral alumina-supported sodium carbonate 'Na2CO3/n-Al2O3'

In the synthesis of dipeptides (Boc‐AA1‐AA2‐OPac: AA1 and AA2 represent amino acids) protected by phenacyl (Pac) ester, amines and solid bases as the base for the conversion of the trifluoroacetic acid (TFA) salt of the amino component (TFA·H‐AA2‐OPac) into the corresponding free amino component (H‐AA2‐OPac) were examined. The synthesis of a dipeptide (Boc‐Ala‐Gly‐OPac) using amines for the conversion afforded an unsatisfactory yield with by‐products. On the other hand, the use of neutral alumina‐supported Na2CO3 (Na2CO3/n‐Al2O3) as a solid base for the conversion provided the dipeptide in a quantitative yield without by‐products. The application of Na2CO3/n‐Al2O3 to the synthesis of some dipeptides protected by Pac ester gave the desired peptides in excellent yields. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd. In the synthesis of dipeptides (Boc‐AA1‐AA2‐OPac: AA1 and AA2 represent amino acids) protected by phenacyl (Pac) ester, amines and solid bases as the base for the conversion of the trifluoroacetic acid (TFA) salt of the amino component (TFA·H‐AA2‐OPac) into the corresponding free amino component (H‐AA2‐OPac) were examined. The synthesis of a dipeptide (Boc‐Ala‐Gly‐OPac) using neutral alumina‐supported Na2CO3 (Na2CO3/n‐Al2O3) as a solid base for the conversion provided the dipeptide in a quantitative yield without by‐products compared with the synthesis employing amines. The application of Na2CO3/n‐Al2O3 to the synthesis of some dipeptides protected by Pac ester gave the desired peptides in excellent yields.