2-Amino-1,7-dihydro-6H-purin-6-one monohydrochloride 635-39-2 6853-89-0 6H-Purin-6-one, 2-amino-1,7-dihydro-, monohydrochloride EINECS 211-235-5 Guanine hydrochloride Guanine, hydrochloride Guanine, monohydrochloride NSC 3702 USAF S-1