(3S,4R)-1-tert-Butyl 3-methyl 4-(8-pivaloyl-5,6,7, 8-tetrahydro-1,8-naphthyridin-3-yl)pyrrolidine-1,3(3S,4R)-1-tert-butyl 3-methyl 4-(8-pivaloyl-5,6,7,8-tetrahydro-1,8-naphthyridin-3-yl)pyrrolidine-1,3-dicarboxylate(3S,4R)-1-tert-butyl 3-methyl 4-(8-pivaloyl-5,6,7,8-tetrahydro-1,8-naphthyridin-3-yl)pyrrolidine-1,3-dicarboxylate