Hydrolysis alkylated pseudoephedrine amides

Alkylation products of pseudoephedrine amides are readily transformed in a single operation into highly enantiomerically enriched carboxylic acids, aldehydes, ketones, lactones or primary alcohols. Alkylated pseudoephedrine amides can be hydrolyzed under acidic or basic conditions to form carboxylic acids. Simply heating a pseudoephedrine amide at reflux in a 1 1 mixture of sulfuric acid (9-18 N) and dioxane affords the corresponding carboxylic acid in excellent chemical yield with little or no epimerization (eq 7). Under these conditions, the substrate initially undergoes a rapid N— -0 acyl transfer reaction followed by rate-limiting hydrolysis of the resulting (3-ammonium ester intermediate to form the carboxylic acid. ... 

Hydrolysis reactions of alkylated pseudoephedrine glycina-mides are more rapid than the hydrolysis of pseudoephedrine amides without a-amino groups. It is believed that this reflects... 

The series on asymmetric synthesis then concludes with procedures for the preparation of enantiomerically pure products. The asymmetric syntheses of unnatural a-amino acids by the alkylation of pseudoephedrine glycin-amide is nicely exemplified by the preparation of l-ALLYLGLYCINE and N-BOC-i.-ALLYLGLYCINE. One of the advantages of this method is the ready availability of the chiral auxiliary and the mildness of the conditions required for the hydrolysis of the pseudophedrine amide to provide the a-amino acid. Biocatalytic transformations are also gaining importance in asymmetric synthesis as illustrated by the preparation of... 

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