tert-butyl 2-amino-5H,6H,7H,8H-pyrido[4,3-d]pyrimidine-6-carboxylatetert-Butyl 2-amino-7,8-dihydropyrido-[4,3-d]pyrimidine-6(5H)-carboxylate6-Boc-2-amino-7,8-dihydro-5H-pyrido[4,3-d]pyrimidinetert-butyl 2-amino-7,8-dihydropyrido[4,3-d]pyrimidine-6(5H)-carboxylate