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