Patent ID: 7396660

Claim:
A method for the preparation of a 23-oxo-LL-F28249 compound, which comprises the following steps of: (a) mutating a module 3 ketoreductase domain of a polyketide synthase gene cluster to render said ketoreductase domain nonfunctional wherein the polyketide synthase gene cluster is responsible for the biosynthesis of an LL-F28249 compound and wherein said module 3 ketoreductase domain either has the amino acid sequence from position 3287 through position 3466, inclusive, of SEQ ID NO:6 or has a nucleotide sequence region that hybridizes at about 42° C. in a solution containing 6×SSC and 50% formamide with a nucleic acid molecule having the nucleic acid sequence from position 29,723 to position 30,262, inclusive, of SEQ ID NO:1; (b) transforming or transfecting an antibiotic-producing wild-type or mutant Streptomyces strain with the mutated nucleic acid molecule to replace the original module 3 ketoreductase domain with the mutated module 3 ketoreductase domain; (c) culturing the transformed or transfected Streptomyces strain in a suitable nutrient medium in a manner allowing production of the 23-oxo-LL-F28249 compound; and (d) recovering the 23-oxo-LL-F28249 compound.