The present invention relates to compounds represented by formula IA or pharmaceutically acceptable salts and solvates thereof which are useful for treating flaviviridae viral infections wherein R 1 is C 1-6 alkyl or C 3-6 cycloalkyl; X is M is R 5 is cyclohexyl which is unsubstituted or substituted one or more times by R 13 ; R 6 is or cyclohexyl which is substituted in the 4 position by R 14 ; and Y, R 14a and R 14 are as defined herein.