Production of anthracycline antibiotic

PURPOSE:To safely and economically obtain an anthracycline antibiotic without using a poisonous reducing agent in high yield by reacting a specific compound with an amine borane complex based reducing agent in the presence of a dioxane-diol. CONSTITUTION:A compound of formula I or its acid addition salt is made to react with a reducing agent of the formula R.BH3 (R is organic amine) (preferably dimethylamine borane, trimethylamine borane, triethylamine borane, t-butylamine borane, pyrrolidine borane or pyridine borane) in the presence of 1,4-dioxane-2,6-diol to provide the objective compound of formula II.