Provided is a dynamic resolution method of enriching a desired isomer of
an alpha-substituted carboxylic acid relative to an undesired isomer, the
method comprising: (a) in a solvent, contacting the alpha-substituted
carboxylic acid, wherein the alpha substitution is with a leaving group
and wherein the alpha carbon is chiral, with a homochiral amine to form a
salt that is partially insoluble under selected reaction conditions,
wherein the homochiral amine is selected so that the solubility of the
amine salt of the undesired alpha-substituted carboxylic acid is greater
than that of the amine salt of the desired alpha-substituted carboxylic
acid under the selected reaction conditions; (b) reacting under the
selected reaction conditions the salt with a nucleophile, wherein the
reacting is effective in producing a net increase in the less soluble
amine salt of the alpha-substituted carboxylic acid, and wherein the
selected conditions are selected to (i) promote nucleophilic substitution
of the nucleophile and the leaving group or (ii) to produce the increase
in the less soluble amine salt in the absence of a strong base; and (c)
maintaining the reaction for a period of time effective to increase the
amount of the desired alpha-substituted carboxylic acid isomer.