2-O-(1-methoxy-2-methyl-1-oxopropan-2-yl) 1-O-methyl (1R)-6-[(3-chloro-2,6-difluorophenyl)methoxy]-3,4-dihydro-1H-isoquinoline-1,2-dicarboxylate;2-methylbut-3-yn-2-yl (1S)-6-[(3-methoxy-6-methylpyridin-2-yl)methoxy]-1-propan-2-yl-3,4-dihydro-1H-isoquinoline-2-carboxylate;1-O-methyl 2-O-(2-methylbut-3-yn-2-yl) (1R)-6-[(3-methoxy-6-methylpyridin-2-yl)methoxy]-3,4-dihydro-1H-isoquinoline-1,2-dicarboxylate;1-O-methyl 2-O-(2-methyl-3-oxopentan-2-yl) (1R)-6-[(3-methoxy-6-methylpyridin-2-yl)methoxy]-3,4-dihydro-1H-isoquinoline-1,2-dicarboxylate;(2-methyl-3-oxopentan-2-yl) (1S)-6-[(3-methoxy-6-methylpyridin-2-yl)methoxy]-1-propan-2-yl-3,4-dihydro-1H-isoquinoline-2-carboxylate