N-Nitroso-Vancomycin Impurity 28

(3S,6R,7R,22R,23S,26R,36R,38aR) -44- (((2S,3R,4S,5S,6R) -3- (((2S,4S,5S,6S) -4-amino-5-hydroxy-4,6-dimethyltetrahydro-2H-pyran-2-yl) oxy) -4,5-dihydroxy-6- (hydroxymethyl) tetrahydro-2H-pyran-2-yl) oxy) -3- (carboxymethyl) -19,45-dichloro-7,22,28,30,32-pentahydroxy-6- ((R) -4-methyl-2- (methyl (nitroso) amino) pentanamido) -2,5,24,38,39-pentaoxo-2,3,4,5,6,7,23,24,25,26,36,37,38,38a-tetradecahydro-1H,22H-23,36- (epiminomethano) -8,11:18,21-dietheno-13,16:31,35-di (metheno) benzo[n][1]oxa[6,9]diazacyclohexadecino[4,5-d][1]oxa[7,17]diazacyclotetracosine-26-carboxylic acid