Nonanamide, 9-(O-.alpha.-D-mannopyranosyl-(1?3)-O-.alpha.-D-mannopyranosyl-(1?6)-.alpha.-D-mannopyranosyl)oxy-N-2-(2,4,5,7-tetrabromo-3,6-dihydroxy-3-oxospiroisobenzofuran-1(3H),9-9Hxanthen-5-yl)aminothioxomethylaminoethyl-