Patent ID: 7365174

Claim:
A compound represented by the following general formula (1) or a pharmaceutically acceptable salt thereof: [wherein: R 1 represents hydrogen atom, or a linear C1-6 alkylcarbonyl group, R 2 represents hydrogen atom, or a C1-6 alkylcarbonyl group, R 3 represents hydrogen atom, a C1-6 alkyl group, a C1-6 alkylcarbonyl group, a C1-6 alkenyl group, a C2-6 alkenylcarbonyl group, a C2-6 alkynyl group, or an Ar—B— group (wherein Ar represents an aryl group, or a heterocyclic group, and B represents a C1-6 alkyl group, a C1-6 alkylcarbonyl group, a C2-6 alkenyl group, a C2-6 alkenylcarbonyl group, or a C2-6 alkynyl group), R 5 , R 6 , R 7 , and R 8 may be the same or different, and represent hydrogen atom, a C1-6 alkyl group, a C2-6 alkenyl group, a C2-6 alkynyl group, or an Ar—B′— group (wherein Ar has the same meaning as that defined above, and B′ represents a C1-6 alkyl group, a C2-6 alkenyl group, or a C2-6 alkynyl group), X represents oxygen atom, or an —NR 4 — group (wherein R 4 represents hydrogen atom, a C1-6 alkyl group, or a C1-6 alkyl group which may be substituted with an Ar group (wherein Ar has the same meaning as that defined above)), and R 4′ represents hydrogen atom, or a group represented by the following formula (a): (wherein R 3″ and R 4″ may be the same or different, and represent hydrogen atom, or a linear or branched C1-6 alkylcarbonyl group)].