Process for producing pyripyropene derivatives and intermediates for the production thereof

A process for producing compound C represented by formula C:

• wherein R′ represents cyclic C3-6 alkylcarbonyl, the process comprising:
• acylating hydroxyl at the 1- and 11-positions of compound Fb represented by formula Fb:
• wherein
• R1b represents formyl;
• optionally substituted straight chain C1-4 alkylcarbonyl;
• optionally substituted benzyl;
• group —SiR3R4R5 optionally substituted by halogen atom wherein R3, R4, and R5 each independently represent straight chain or branched chain C1-6 alkyl or phenyl;
• C1-6 alkyloxy-C1-6 alkyl optionally substituted by halogen atom;
• C1-6 alkylthio-C1-6 alkyl optionally substituted by halogen atom;
• straight chain, branched chain, or cyclic C1-4 alkyl optionally substituted by halogen atom, provided that, when alkyl in the C1-4 alkyl group is of a branched chain or cyclic type, the alkyl group is C3-4 alkyl;
• C2-6 alkenyl optionally substituted by halogen atom;
• C2-6 alkynyl optionally substituted by halogen atom;
• or an optionally substituted saturated or unsaturated five- or six-membered heterocyclic group,
• wherein, in R1b, the substituent optionally possessed by alkylcarbonyl is selected from the group consisting of halogen atoms, C1-4 alkyloxy, C1-4 haloalkyloxy, C1-4 alkylcarbonyl, C1-4 haloalkylcarbonyl, C1-4 alkylcarbonyloxy, and C1-4 haloalkylcarbonyloxy, and the substituent optionally possessed by the heterocyclic group and benzyl is selected from the group consisting of halogen atoms, C1-4 alkyl, C1-4 alkyloxy, C1-4 haloalkyloxy, C1-4 alkylthio, C1-4 haloalkyl, C1-4 alkylcarbonyl, C1-4 haloalkylcarbonyl, C1-4 alkylcarbonyloxy, C1-4 haloalkylcarbonyloxy, nitro, and cyano,
• with an acylating agent corresponding to R′ as defined above to give compound B2b represented by formula B2b:
• wherein R1b and R′ are as defined above,
• and then removing R1b of compound B2b to produce compound C.