Polysaccharide derivative and separating agent for optical isomer containing the same

The present invention relates to a polysaccharide derivative useful in separating optical isomers, and a separating agent for optical isomers containing the polysaccharide derivative.

A polysaccharide derivative obtained by modifying the hydroxyl groups or amino groups of a polysaccharide with various substituents is known to serve as a chiral stationary phase in chromatography to show a high optical resolution, and a large number of kinds of polysaccharide derivatives have been heretofore synthesized.

Examples of such polysaccharide derivative useful as a separating agent for optical isomers include: an ester derivative of a polysaccharide (see, for example, Patent Document 1); an alkyl-substituted phenylcarbamate of a polysaccharide except cellulose (see, for example, Patent Document 2); a chitosan derivative (see, for example, Patent Document 3); a cyclodextrin derivative (see, for example, Patent Document 4); a polysaccharide derivative obtained by substituting the hydroxyl groups or amino groups of a polysaccharide with two or more kinds of different substituents (see, for example, Patent Document 5); a polysaccharide derivative obtained by specifically introducing a substituent into the 2-position of a polysaccharide (see, for example, Non-patent Document 1); and a polysaccharide derivative obtained by specifically introducing a substituent into the 6-position of a polysaccharide by the protection of a hydroxyl group at the 6-position by a trityl group and deprotection (see, for example, Non-patent Document 2).

However, a polysaccharide derivative having a specific kind of a substituent at a specific position, in particular a polysaccharide derivative having specific substituents different from each other at its 2- and 3-positions that are hard to distinguish in the introduction of a substituent into a hexose leaves room for future studies.

Non-Patent Document 2: Macromol. Chem. Phys. 1996, 197, 953

The present invention provides a novel polysaccharide derivative excellent in optical isomer separating ability and suitable for a separating agent for optical isomers, and a separating agent for optical isomers containing the polysaccharide derivative.

The present invention provides a polysaccharide derivative having different kinds of substituents introduced into its 2- and 3-positions. In particular, the present invention provides a polysaccharide derivative obtained by substituting hydroxyl groups or amino groups at the 3- and 6-positions of a polysaccharide with substituents of one kind different from that at a 2-position of the polysaccharide, a polysaccharide derivative obtained by randomly substituting hydroxyl groups or amino groups at the 3- and 6-positions of a polysaccharide with substituents of two kinds different from that at a 2-position of the polysaccharide, and a polysaccharide derivative obtained by substituting hydroxyl groups or amino groups at the 3- and 6-positions of a polysaccharide with substituents of two kinds different from that at a 2-position of the polysaccharide. Further, the present invention provides, as a method of producing any such polysaccharide derivative, a method involving: specifically introducing a substituent into only a hydroxyl group or amino group at a 2-position of a polysaccharide; and introducing a substituent different from the substituent at the 2-position into at least a 3-position of the polysaccharide. Further, the present invention provides a method involving: specifically introducing a substituent into a hydroxyl group or amino group at the 2-position of a hexose; protecting a hydroxyl group or amino group at the 6-position of the hexose after the introduction; introducing a substituent different from the substituent at the 2-position into a hydroxyl group or amino group at the 3-position of the hexose; deprotecting the 6-position; and specifically introducing a substituent into the 6-position.

In addition, the present invention provides, as the method of producing the polysaccharide derivative, a method involving: protecting a hydroxyl group or amino group at a 2-position of a polysaccharide; introducing a specific substituent into at least a 3-position of the polysaccharide; deprotecting the 2-position after the introduction; and introducing another specific substituent into the 2-position. Further, the present invention provides a method involving: protecting a hydroxyl group or amino group at the 2-position of a hexose; introducing a specific substituent into each of the 3- and 6-positions of the hexose; and introducing another specific substituent into the 2-position when deprotecting only the 2-position, or introducing another specific substituent into each of the 2- and 6-positions when deprotecting the 2-position and demodifying the 6-position.

In addition, the present invention provides, as the method of producing the polysaccharide derivative, a method involving: protecting a hydroxyl group or amino group at the 2-position of a hexose; protecting a hydroxyl group or amino group at the 6-position of the hexose after the protection; introducing a specific substituent into a hydroxyl group or amino group at the 3-position of the hexose; deprotecting the 6-position; introducing a specific substituent different from that at the 3-position into the 6-position; deprotecting the 2-position; and introducing a specific substituent different from those at the 3- and 6-positions into the 2-position.

That is, the present invention provides a polysaccharide derivative including a structure in which hydrogen atoms of at least hydroxyl groups or amino groups at 2- and 3-positions out of hydroxyl groups or amino groups of structural units of a polysaccharide are substituted with different substituents each represented by any one of the following general formulae (I) to (III):

—CO—R  (I)