The present invention provides compounds of formula (I)wherein R1, R2, R3, R4, R5, R6, R7, R8, R8', R9, R9', X1, X2, X3, X4, X5, X6, X7, X8, X9 and X10 are as described herein, as well as pharmaceutically acceptable salts thereof. Further the present invention is concerned with the manufacture of the compounds of formula (I), pharmaceutical compositions comprising them and their use as medicaments for the treatment of diseases and infections caused by Acinetobacter baumannii.