Patent ID: 8853413

Claim:
A process for producing a compound C represented by formula C: wherein R represents a straight chain, branched chain, or cyclic C 2-6 alkylcarbonyl, provided that, when the alkyl moiety in the alkylcarbonyl group is of a branched chain or cyclic type, then R represents C 3-6 alkylcarbonyl, the process comprising: selectively acylating hydroxyl groups at the 1-position and 11-position of a compound B1 represented by formula B1: with an acylating agent in an amount of 2.0 to 5.0 equivalents based on the amount of the compound B1, through one to three steps in the presence or absence of a base, in an aprotic polar organic solvent selected from the group consisting of N,N-dimethylformamide, dimethylsulfoxide, N,N-dimethylacetamide, acetonitrile, N-methyl-2-pyrrolidinone, N-methyl-2-piperazinone and N,N-dimethyl-2-imidazolidinone, to obtain the compound C.