Method for producing pentacyclic taxans

1. A method for producing a compound of the following general formula (2) or its salt, which comprises reacting a compound of the following formula (1) with an alkali metal permanganate:

(in formula (1), the dotted line part between the 6-position and the 7-position of the partial structure of the following formula (1-a):

means that the bond of this part may be a double bond; boc means a tert-butoxycarbonyl group; Ac means an acetyl group; Bz means a benzoyl group; R 1 means an alkyl group, a cycloalkyl group, a phenyl group or a monocyclic heterocyclic group, and the alkyl group, the cycloalkyl group, the phenyl group or the monocyclic heterocyclic group may be have one or more substituents selected from a group consisting of a halogen atom, an alkyl group, an alkoxy group, a phenyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, an acylamino group and an acyloxy group; R 2 means a hydroxyl group optionally having a protective group);

(in formula (2), R 1 , R 2 , boc, Ac and Bz have the same meanings as above).

2. The production method as claimed in claim 1 , which comprises reacting a compound of the following general formula (4):

(in formula (4), the dotted line part between the 6-position and the 7-position of the partial structure of the following formula (4-a):

means that the bond of this part may be a double bond; boc means a tert-butoxycarbonyl group; Ac means an acetyl group; Bz means a benzoyl group; R 4 means a halogen atom or an alkoxy group; n indicates an integer of from 0 to 4; when n is 2 or more, then two or more R 4 's may be the same or different; R 5 means a hydroxyl group optionally having a protective group),

with an alkali metal permanganate in the presence of a base in at least one solvent selected from a group consisting of aqueous pyridin, aqueous tetrahydrofuran and aqueous acetone to produce a compound of the following general formula (5) or its salt, or their hydrate or solvate:

(in formula (5), R 4 , n, R 5 , boc, Ac and Bz have the same meanings as above).

3. The production method as claimed in claim 1 , which comprises reacting a compound of the following general formula (7):

(in formula (7), boc means a tert-butoxycarbonyl group; Ac means an acetyl group; Bz means a benzoyl group; and TIPS means a triisopropylsilyl group),

with potassium permanganate in the presence of lithium hydroxide in aqueous pyridine to produce a compound of the following general formula (8) or its salt:

(in formula (8), boc, Ac, Bz and TIPS have the same meanings as above).

4. A method for producing a compound of the following general formula (3) or its salt, which comprises;

1) a step of reacting a compound of the following general formula (1):

 (in formula (1), the dotted line part between the 6-position and the 7-position of the partial structure of the following formula (1-a):

means that the bond of this part may be a double bond; boc means a tert-butoxycarbonyl group; Ac means an acetyl group; Bz means a benzoyl group; R 1 means an alkyl group, a cycloalkyl group, a phenyl group or a monocyclic heterocyclic group, and the alkyl group, the cycloalkyl group, the phenyl group or the monocyclic heterocyclic group may be have one or more substituents selected from a group consisting of a halogen atom, an alkyl group, an alkoxy group, a phenyl group, an alkylaminoalkyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, an acylamino group and an acyloxy group; R 2 means a hydroxyl group optionally having a protective group), with an alkali metal permanganate to obtain a compound of the following general formula (2):

(in formula (2), R 1 , R 2 , boc, Ac and Bz have the same meanings as above);

2) a step of converting the group —CH(OH)CH 2 OH in the compound of formula (2) into a group —R 3 {in which R 3 means an alkyl group, substituted with an alkylamino group, a dialkylamino group or a morpholine group};

3) when the bond between the 6-positioned carbon and the 7-positioned carbon is a double bond, a step of converting it into a single bond; and

4) when R 2 is a hydroxyl group having a protective group, a step of removing the protective group:

(in formula (3), R 1 , R 3 , boc, Ac and Bz have the same meanings as above).

5. The production method as claimed in claim 4 , which produces a compound of the following general formula (6) or its salt, and comprises;

1) a step of reacting a compound of the following general formula (4):

 (in formula (4), the dotted line part between the 6-position and the 7-position of the partial structure of the following formula (4-a):

 means that the bond of this part may be a double bond; boc means a tert-butoxycarbonyl group; Ac means an acetyl group; Bz means a benzoyl group; R 4 means a halogen atom or an alkoxy group; n indicates an integer of from 0 to 4; when n is 2 or more, then two or more R 4 's may be the same or different; R 5 means a hydroxyl group optionally having a protective group),

 with an alkali metal permanganate in the presence of a base in at least one solvent selected from a group consisting of aqueous pyridin, aqueous tetrahydrofuran and aqueous acetone to obtain a compound of the following general formula (5):

 (in formula (5), R 4 , n, R 5 , boc, Ac and Bz have the same meanings as above),

2) a step of converting the group —CH(OH)CH 2 OH in the compound of formula (5) into a dimethylaminomethyl group or a morpholinomethyl group;

3) when the bond between the 6-positioned carbon and the 7-positioned carbon is a double bond, a step of converting it into a single bond; and

4) when R 5 is a hydroxyl group having a protective group, a step of removing the protective group:

 (in formula (6), R 4 , n, boc, Ac and Bz have the same meanings as above; R 6 means a dimethylaminomethyl group or a morpholinomethyl group).