3'-(4-Guanidinobenzoyloxy)spiro(isobenzofuran-1-(3H),9'-(9H)xanthen)-3-one 3-Hfgb 3HFGB 97165-32-7 Benzoic acid, 4-((aminoiminomethyl)amino)-, 3-oxospiro(isobenzofuran-1(3H),9'-(9H)xanthen)-3'-yl ester