Compounds according to the general formula and pharmaceutically acceptable salts or prodrugs of said compounds, in which - R 1 is in the second, third or fourth position and is selected from -H or R 2 -CO-NH-CH 2 -, in which R 2 is a linear or branched alkyl group having from 1 to 9 carbon atoms; and - P3 is a mono- or polysubstituted or unsubstituted, natural or unnatural α-amino acid in D-configuration, that is to say P3 is a structure according to formula in which - m = 0, 1, 2, 3, 4 or 5, and - R 4 is selected from • an unsubstituted or optionally substituted hydroxyl-, amino-, amide-, -S-CH 3 -, amidino-, guanidino- or -O-guanidino group having the following structures wherein independently of one another R 5, R 6 and R 7 may be a H- or an aralkyl functional group, or • from an unsubstituted aryl- or heteroaryl ring, or from an aryl- or heteroaryl ring substituted at any position, having from 5 to 10 ring atoms, wherein the heteroaryl ring may contain up to 4 heteroatoms selected from N, O or S, and the optionally existing substituent at the aryl- or heteroaryl ring is selected from cyano-, CF 3 -, F-, Cl-, Br-, amino-, aminomethylene-, amidino-, guanidino groups or from the following structures wherein the functional groups R 5, R 6 and R 7 are defined as above, or • from an unsubstituted cycloalkyl ring, or a cycloalkyl ring substituted at any position, having from 5 to 7 ring atoms; and - P2 is a mono- or polysubstituted or unsubstituted, natural or unnatural α-amino acid or α-imino acid in L-configuration, that is to say P2 is an α-amino acid group or α-imino acid functional group according to the following structures, - wherein n may be equivalent to 0, 1 or 2 and m and R 4 are defined as above, and if m is equivalent to 0 or 1, R 4 may be H; and - P1 is selected from the following structures in which R 3 is a H, or in the case of the prodrug is an OH, O-CH 3, O-CO-CH 3 or -CO-O-(CH 2) Z -CH 3 and z is an integer from 1 to 5, for use in the treatment and/or prevention of viral infections and inflammatory respiratory diseases by inhibiting the serine proteases HAT and TMPRSS2. - R 1 is in the second, third or fourth position and is selected from -H or R 2 -CO-NH-CH 2 -, in which R 2 is a linear or branched alkyl group having from 1 to 9 carbon atoms; and - P3 is a mono- or polysubstituted or unsubstituted, natural or unnatural α-amino acid in D-configuration, that is to say P3 is a structure according to formula - m = 0, 1, 2, 3, 4 or 5, and - R 4 is selected from • an unsubstituted or optionally substituted hydroxyl-, amino-, amide-, -S-CH 3 -, amidino-, guanidino- or -O-guanidino group having the following structures wherein independently of one another R 5, R 6 and R 7 may be a H- or an aralkyl functional group, or • from an unsubstituted aryl- or heteroaryl ring, or from an aryl- or heteroaryl ring substituted at any position, having from 5 to 10 ring atoms, wherein the heteroaryl ring may contain up to 4 heteroatoms selected from N, O or S, and the optionally existing substituent at the aryl- or heteroaryl ring is selected from cyano-, CF 3 -, F-, Cl-, Br-, amino-, aminomethylene-, amidino-, guanidino groups or from the following structures wherein the functional groups R 5, R 6 and R 7 are defined as above, or • from an unsubstituted cycloalkyl ring, or a cycloalkyl ring substituted at any position, having from 5 to 7 ring atoms; and • an unsubstituted or optionally substituted hydroxyl-, amino-, amide-, -S-CH 3 -, amidino-, guanidino- or -O-guanidino group having the following structures wherein independently of one another R 5, R 6 and R 7 may be a H- or an aralkyl functional group, or • from an unsubstituted aryl- or heteroaryl ring, or from an aryl- or heteroaryl ring substituted at any position, having from 5 to 10 ring atoms, wherein the heteroaryl ring may contain up to 4 heteroatoms selected from N, O or S, and the optionally existing substituent at the aryl- or heteroaryl ring is selected from cyano-, CF 3 -, F-, Cl-, Br-, amino-, aminomethylene-, amidino-, guanidino groups or from the following structures wherein the functional groups R 5, R 6 and R 7 are defined as above, or • from an unsubstituted cycloalkyl ring, or a cycloalkyl ring substituted at any position, having from 5 to 7 ring atoms; and • from an unsubstituted aryl- or heteroaryl ring, or from an aryl- or heteroaryl ring substituted at any position, having from 5 to 10 ring atoms, wherein the heteroaryl ring may contain up to 4 heteroatoms selected from N, O or S, and the optionally existing substituent at the aryl- or heteroaryl ring is selected from cyano-, CF 3 -, F-, Cl-, Br-, amino-, aminomethylene-, amidino-, guanidino groups or from the following structures wherein the functional groups R 5, R 6 and R 7 are defined as above, or • from an unsubstituted cycloalkyl ring, or a cycloalkyl ring substituted at any position, having from 5 to 7 ring atoms; and - P2 is a mono- or polysubstituted or unsubstituted, natural or unnatural α-amino acid or α-imino acid in L-configuration, that is to say P2 is an α-amino acid group or α-imino acid functional group according to the following structures, - wherein n may be equivalent to 0, 1 or 2 and m and R 4 are defined as above, and if m is equivalent to 0 or 1, R 4 may be H; and - P1 is selected from the following structures in which R 3 is a H, or in the case of the prodrug is an OH, O-CH 3, O-CO-CH 3 or -CO-O-(CH 2) Z -CH 3 and z is an integer from 1 to 5,