Abstract: This invention relates to a DNA molecule or a functional derivative thereof coding for a fusion protein, the fusion protein comprising an enzymatically active component and a non-enzymatically active polypeptide component which may be cleaved therefrom, an expression system which contains the DNA molecule, the use thereof as a test system for inhibitors of viral proteases, and an assay for identifying viral inhibitors.

Abstract: A process for the preparation of L-aspartyl-(O-sulfato-L-tyrosyl)-L-methionyl-glycyl-L-tryptophyl-L-methion yl-L-aspartyl-L-phenylalanine amide, which comprises treating the protected octapeptide amide of the general formula (II) ##STR1## wherein X is BOC, Cbz or Ddz,Y is O.sup.t Bu, OBzl or OH andW is O.sup.t Bu, OBzl or OH,in the presence of an ether with an excess of the complex compound of sulfur trioxide and a tertiary amine containing at least one alkyl group, converting the obtained sulfate ester of the protected octapeptide amide into an alkali metal salt and simultaneously removing the formyl group from the tryptophan unit by reacting the sulfate ester with an alkali metal hydroxide, and then splitting off the remaining protective groups by acidolysis.