The reaction of maltose (I) with isobutylamine (II) in methanol at 65 C gives isobutylmaltosylamine (III), which is condensed with 2-chloroethyl isocyanate (IV) yielding 1-(2-chloroethyl)-3-isobutyl-3-D-maltosylurea (V). The nitrosation of (V) with dinitrogen tetroxide in THF in the presence of sodium acetate gives 1-(2-chloroethyl)-3-isobutyl-3-(beta-D-heptanitrosomaltosyl)-1-nitrosourea (VI). The nitrous esters of (VI) can be decomposed without affecting the N-nitroso group by addition of methanol under acidic conditions to give TA-077 in good yield.