Polyion complex of poly(L-arginine) segment-containing block copolymer and polyanionic polymer

1. A method for producing a block copolymer represented by formula (I):

wherein:

A is

(i) hydrogen, a C 1 -C 12 alkyl group optionally substituted with a formyl group, or a group of the formula R 1 R 2 CH—, wherein R 1 and R 2 independently represent C 1 -C 4 alkoxy or R 1 and R 2 together represent —OCH 2 CH 2 O—, —O(CH 2 ) 3 O—, or —O(CH 2 ) 4 O—, or

(ii) a group of the formula:

wherein L and L′ independently is a linkage group;

Y and Y′ independently is H, C 1-21 alkylcarbonyl, substituted C 1-4 alkylcarbonyl, optionally substituted C 3-7 cycloalkylcarbonyl, optionally substituted arylcarbonyl, optionally substituted 5-membered heteroarylcarbonyl, or optionally substituted 6-membered heteroarylcarbonyl,

wherein the substituted C 1-4 alkylcarbonyl is substituted with a substituent selected from the group consisting of a halogen atom, hydroxyl, carboxyl, optionally substituted C 3-7 cycloalkyl, optionally substituted aryl, optionally substituted 5-membered heteroaryl, optionally substituted 6-membered heteroaryl, optionally substituted adamantyl and a cholesterol residue,

wherein the optionally substituted C 3-7 cycloalkyl, optionally substituted aryl, optionally substituted 5-membered heteroaryl, optionally substituted 6-membered heteroaryl and optionally substituted adamantyl are optionally substituted with a substituent selected from the group consisting of C 1-4 alkyl, C 1-4 alkyloxy, hydroxyl, carboxyl, cyano, nitro, a halogen atom mono-C 1-4 alkylamino and di-C 1-4 alkylamino, and

wherein the cholesterol residue is a cholesterol molecule from which H is eliminated on a carbon at position 22 to 27 or from which a hydrocarbon chain is eliminated;

m and m′ are independently an integer of 5 to 300;

n is an integer of 5 to 1,000; and

up to 80% of m or m′ amidino groups (C(═NH)NH 2 ) are H,

the method comprising a step of reacting a block copolymer represented by formula (II):

wherein:

A is

(i)′ (i) as defined for formula (I) above, or

(ii)′ a group the formula:

wherein L, L′, Y, Y′, n, m and m′ are as defined for formula (I) above,

with N,N′-bis(tert-butoxycarbonyl)-1H-pyrazole-1-carboxamidine optionally in an inert solvent in order to convert a δ-amino group in a segment derived from ornithine to a guanidino group.

2. The method for producing a block copolymer according to claim 1 , wherein A in formula (II) is (i)′.

3. The method for producing a block copolymer according to claim 1 , wherein A in formula (II) is (ii)′.