Abstract: Disclosed is a method for extracting an amino acid ester from a hydrous solution which comprises adding thereto a water-insoluble organic solvent and then an amount of a base effective to liberate only a portion of the amino acid ester in free base form, and transferring the thus liberated amino acid ester in the free base form into the organic layer, and repeating the neutralization-extraction steps until all of the amino acid ester has been extracted.

Abstract: 6-Methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide is prepared bya) reacting, in an inert organic solvent, a salt of sulfamic acid, which is at least partially soluble therein, with at least approximately the equimolar amount of an acetoacetylating agent, in the presence of an amine or phosphine catalyst, and by cyclizing the acetoacetamide-N-sulfonate which is formed in this reaction, or the free sulfonic acid,b) by the action of at least approximately the equimolar amount of SO.sub.3, where appropriate in an inert inorganic or organic solvent, to give 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide, which is produced in the form of the acid in this reaction;it is possible, if desired, to obtain from the acid formc) the appropriate salts by neutralization with bases. The non-toxic salts--in particular the potassium salt--are valuable synthetic sweeteners.