The invention relates to compounds of formula (I):or a salt thereof, wherein R1, A, L, and R2and n are as described herein. Compounds of formula (I) and pharmaceutical compositions thereof are αvβ1 integrin inhibitors that are useful for treating tissue specific fibrosis.本發明係關於式(I)化合物:或其鹽,其中R1、A、L及R2及n如本文所述。式(I)化合物及其醫藥組合物為適用於治療組織特異性纖維化的αvβ1整合素抑制劑。