| abstract |
The compounds of formula I wherein R1 is alkyl or trifluoromethyl, R2, R3 and R4 independently are hydrogen or a carboxy-protecting group and R5 is hydrogen or alanyl optionally protected at the amino moiety thereof, with the proviso that when R2, R3 and R4 simultaneously are hydrogen, then R5 is hydrogen, in free form or as appropriate in salt form, possess pharmacological activity. In particular they modulate unspecific antimicrobial resistance and possess particularly low pyrogenicity. They are indicated for use as immunomodulators and antiviral and anti-tumor agents. They can be prepared by reaction with a glyoxylic acid derivative or reaction with an alanyl derivative, where appropriate followed by deprotection. |