New block copolymer micelle preparation and antineoplastic agent containing it as an active ingredient

A block copolymer obtained by reacting a compound represented by the following general formula (1): ** ** Formula wherein R1 represents a hydrogen atom or an alkyl group I (C1 to C5), R2 represents an alkylene group (C1 to C5), R3 represents a methylene group or an ethylene group, R4 represents a hydrogen atom or an acyl group (C1 to C4), R5 represents a hydroxyl group, an optionally substituted (C1 to C8) aryl group or a group - N (R6) -CO-NHR 7, R6 and R7 may be the same or different and each represents a cyclic alkyl group (C3 to C6), or an alkyl (C1 to C5) optionally substituted with a tertiary amino group; n represents 5 to 1000, m represents from 2 to 300, x represents from 0 to 300 and y represents from 0 to 300, provided that the sum of x and y is from 1 or more to m or less; and R5 is a hydroxyl group at a ratio of 1 - 99% relative am, an aryl (C1 to C8) group optionally substituted at a proportion of 1 - 99% relative am, and -N (R6) -CO-NHR 7 a proportion of 0 - 10% relative am with a carbodiimide compound in an amount of from m to 5 m equivalents relative to the compound represented by the general formula (1) in a solvent at 30 to 60C for 2 to 48 hours.