The present invention relates to compounds of formula I: wherein R<SUP>1</SUP>, R<SUP>2</SUP>, R<SUP>3</SUP>, R<SUP>4</SUP>, R<SUP>5 </SUP>and R<SUP>6 </SUP>are as defined in the specification and claims, which compounds are active on the GABA<SUB>B </SUB>receptor and are useful in the control or prevention of CNS illnesses, especially of illnesses and disorders comprising anxiety, depression, epilepsy, schizophrenia, and cognitive disorders.
2-phenyl-3,3,3-trifluoro-2-hydroxy-propionic acid derivatives