1. A method of producing a compound of the formula [I]
5 which comprises a step of removing the protecting group from a compound of the formula [III]
to give a compound of the formula [I].
2. A method of producing a compound of the formula [II]
which comprises a step of treating a compound of the formula [I]

I
with hydrogen chloride to give a compound of the formula [II]. 3. A method of producing a compound of the formula [II]
which comprises a step of removing the protecting group from a compound of the formula [III]
to give a compound of the formula [I], and
a step of treating a compound of the formula [I]
with hydrogen chloride to give a compound of the formula [II].

4. The method of claim 1 or 3, which further comprises a step of reacting a compound of the formula [V]
\ /
with a compound of the formula [IV]
or a reactive derivative thereof or a salt thereof to give a
compound of the formula [III]
5. The method of claim 4, which further comprises a step of subjecting a compound of the formula [VI]

wherein R1 and R2 are each independently hydrogen, Ci-6 alkyl or
Ci-6 alkoxy,
to a reduction reaction to give a compound of the formula [V]
6. The method of claim 5, which further comprises a step of reacting a compound of the formula [VII]

wherein R1 is as defined in claim 5, with a compound of the formula [XI]
wherein R2 is as defined in claim 5, 5 to give a compound of the formula [VI]
r
wherein R1 and R2 are as defined above.
7. The method of claim 6, which further comprises a step of 10 subjecting a compound of the formula [VIII]
r
wherein R1 is as defined in claim 5,
to tetrahydropyranylation to give a compound of the formula
[VII]

wherein R is as defined above.
8. The method of claim 1, which further comprises a step of reacting a compound of the formula [IX]
IN
H
with a compound of the formula [X]
wherein
M is sodium or potassium, and
R1 is as defined in claim 5,
to give a compound of the formula [VIII]
wherein R1 is as defined above.
9. The method of claim 2 or 3, which further comprises a step
of purifying a compound of the formula [II]

with 1-propanol.
10. A method of producing a compound of the formula [XI]
wherein R2 is hydrogen, Ci-g alkyl or Ci-6 alkoxy,
which comprises a step of subjecting a compound of the formula
[XII]
wherein R2 is as defined above, to methylation.
11. A compound of the formula [V]

12. A compound of the formula [III]
13. A compound of the formula [VI]
f
wherein R1 and R2 are each independently hydrogen, Ci-g alkyl or Ci-6 alkoxy.
14. A compound of the formula [VII]

wherein R1 is hydrogen, Ci_s alkyl or Ci-6 alkoxy. 15. A compound of the formula [VIII]
y wherein R1 is hydrogen, Ci_6 alkyl or Ci-e alkoxy. 16. A compound of the formula [XI]
t
wherein R2 is hydrogen, Ci-e alkyl or Ci-e alkoxy.
10