Dolbier HW Solutions 670

Dolbier HW Solutions 670 - 764 AMINO ACIDS, PEPTIDES, AND...

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27.25 The following outlines a synthesis of b -alanine in which conjugate addition to acrylonitrile plays a key role. Addition of ammonia to acrylonitrile has been carried out in modest yield (31 33%). Hydrolysis of the nitrile group can be accomplished in the presence of either acids or bases. Hydrolysis in the pres- ence of Ba(OH) 2 has been reported in the literature to give b -alanine in 85 90% yield. 27.26 ( a ) The f rst step involves alkylation of diethyl malonate by 2-bromobutane. In the second step of the synthesis, compound A is subjected to ester saponi f cation. Follow- ing acidi f cation, the corresponding diacid (compound B) is isolated. Compound B is readily brominated at its a -carbon atom by way of the corresponding enol form. When compound C is heated, it undergoes decarboxylation to give an a -bromo carboxylic acid. Treatment of compound D with ammonia converts it to isoleucine by nucleophilic substitution.
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