Abstract: A compound represented by the formula, ##STR1## wherein R.sub.1 represents a hydrogen atom, and R.sub.2 represents a lower alkyl group, an aryl group, an aralkyl group, a lower alkylthio lower alkyl group, a lower alkyl group substituted by a carboxyl or hydroxyl group, or a 3-indolymethyl group, or wherein R.sub.1 and R.sub.2 define in combination an alkylene group, or a pharmaceutically acceptable acid addition salt thereof, is an anti-tumor agent for leukemia and malignant tumors.

Abstract: The specification describes a nitrosourea derivative having the general formula: Cl--(CH.sub.2).sub.2 --N(NO)CO--NHR, wherein --NHR represents a 2-(1,3,4-thiadiazolyl)amino group, an amino residue of a neutral .alpha.-amino acid, or an amino residue of a neutral .alpha.-amino acid whose carboxyl group is amidated with 2-(1,3,4-thiadiazolyl)amine, or a pharmaceutically acceptable acid addition salt thereof. The above nitrosourea derivative and its salt are useful as antitumor drugs. The above nitrosourea derivative may be prepared either by nitrosating a urea derivative of the general formula: Cl--(CH.sub.2).sub.2 NHCONHR or by reacting N-(2-chloroethyl)-N-nitrosocarbamic acid or a reactive derivative thereof with an amino compound of the general formula: R--NH.sub.2.