Pyrazolomorphinan derivative

A compound represented by the following general formula (I), a stereoisomer of the compound, a pharmaceutically acceptable salt thereof, or a solvate thereof:

• in the formula,
• is represented by
• R1 represents a hydrogen atom, a C1-6 alkyl group which may have a substituent, a C2-6 alkenyl group which may have a substituent, or a C3-10 cycloalkylmethyl group which may have a substituent;
• R2 represents a hydrogen atom or a hydroxy protecting group;
• R3 represents a hydroxy group, a C1-6 alkyl group which may have a substituent, a C3-10 cycloalkyl group which may have a substituent, a saturated heterocyclic group which may have a substituent, a partially unsaturated heterocyclic group which may have a substituent, a C6-10 aryl group which may have a substituent, or a 5- to 10-membered heteroaryl group which may have a substituent;
• and
• R4 represents a hydrogen atom, a C1-6 alkyl group which may have a substituent, a C1-12 acyl group which may have a substituent, a C7-12 aralkyl group which may have a substituent, a C3-10 cycloalkyl group which may have a substituent, a C3-10 cycloalkyl C1-6 alkyl group which may have a substituent, a saturated heterocyclic group which may have a substituent, a partially unsaturated heterocyclic group which may have a substituent, a C6-10 aryl group which may have a substituent, or a 5- to 10-membered heteroaryl group which may have a substituent.