Radicicol derivatives

A radicicol derivative represented by formula (I):

• wherein
• R1 and R2 independently represent hydrogen, alkanoyl, alkenoyl, tert-butyldiphenylsilyl or tert-butyldimethylsilyl;
• R3 represents Y—R5, wherein Y represents substituted or unsubstituted alkylene and R5 represents substituted or unsubstituted pyridyl, or substituted or unsubstituted pyridonyl, or
• R3 represents COR13, wherein R13 represents hydrogen, substituted or unsubstituted lower alkyl, substituted or unsubstituted higher alkyl, substituted or unsubstituted aryl, substituted or unsubstituted lower alkoxy, or NR14R15 wherein R14 and R15 independently represent hydrogen, substituted or unsubstituted lower alkyl, substituted or unsubstituted higher alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted pyridyl, or R14 and R15 are combined together with adjoining N to represent a substituted or unsubstituted pyridyl group;
• X represents halogen, or is combined together with R4 to represent a single bond;
• and
• R4 is combined together with X to represent a single bond, or represents hydrogen, alkanoyl, alkenoyl, or —SO—Z, wherein Z is represented by formula (II):
• wherein R1A and R2A have the same meaning as R1 and R2, respectively;
• XA represents halogen;
• and W represents O or N—O—R3A wherein R3A has the same meaning as R3, or a pharmacologically acceptable salt thereof.