Abstract: Reaction of a ketoxime-derivatized resin with a strong acid salt of aspartic anhydride or glutamic anhydride yields a novel aspartyl or glutamyl ketoxime ester-derivatized resin, wherein the aspartyl or glutamyl groups are esterified predominantly at the .alpha.-carboxyl group and wherein the aspartyl or glutamyl groups are not covalently protected at the amino group or the carboxyl group that is not esterified. Aminolysis in the presence of a weak acid of the novel aspartyl or glutamyl ketoxime ester-derivatized resin, wherein the aspartyl or glutamyl groups remain as the strong acid salt, with a salt of an amino acid with a base or an amino acid ester yields the corresponding dipeptide or dipeptide ester. After aminolysis, the ketoxime-derivatized resin can be reused. An advantageous solid-phase method is thus provided for making .alpha.-L-aspartyl dipeptide ester sweeteners, including aspartame, and the immunopotentiating dipeptide, .alpha.-L-glutamyl-L-asparagine.

Abstract: Foreign protein segments having specific medically or commercially useful biological functions are incorporated in surface proteins of viruses. The viruses with the incorporated protein segments are convenient agents for introducing the protein segments into animals, such as humans, and are thus useful as vaccines. Small segments of an original protein exhibiting desired functions are identified, and a DNA fragment having a nucleotide base sequence encoding that segment of the protein is isolated from an organism or synthesized chemically. The isolated DNA fragment is inserted into the DNA genome of a virus in a manner such that the inserted DNA fragment expresses itself as the foreign segment of a surface viral protein and in such a way that neither the function of the protein segment nor the function of any viral protein critical for viral replication is impaired.