Beta-hairpin peptidomimetics of the general formula (I), cyclo[P1-p2-p3-p4-p5-p6-p7-p8-p9-p10-p11-p12-T1-T2], and pharmaceutically acceptable salts thereof, with P1 to P12, T1 and T2 being elements as defined in the description and the claims, have Gram-negative antimicrobial activity to e.g. inhibit the growth or to kill microorganisms such as Klebsiella pneumoniae and/or Acinetobacter baumannii and/or Escherichia coli. They can be used as medicaments to treat or prevent infections or as disinfectants for foodstuffs, cosmetics, medicaments or other nutrient-containing materials. These peptidomimetics can be manufactured by a process which is based on a mixed solid- and solution phase synthetic strategy.