Synthesis of the Protected Dipeptide Ala-Phe-OMe

To convert the diprotected dipeptide Boc-Ala-Phe-OMe (10) into Ala-Phe, it is necessary to remove the protecting groups from the nitrogen atom of the N-terminal L-alanine and the carboxylic acid of the C-terminal L-phenylalanine. This might be accomplished by hydrolysis of both groups under acidic conditions. However, the zwitterionic Ala-Phe is difficult to isolate, so in this experiment you will only selectively remove the Boc group from the L-alanine residue to give 

The conversion of 11 into Ala-Phe (12) requires hydrolysis of the methyl ester, a reaction that may be accomplished by hydrolysis of 11 in aqueous acid or base followed by neutralization to provide 12 (Eq. 24.9). You may have an opportunity to develop a procedure to effect this transformation and isolate 12 if you perform the suggested Discovery Experiment 

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