Rapamycin (1) is a potent immunosuppressive and antiproliferative natural product isolated from the soil actinomycete Streptomyces hygroscopicus NRRL 5491.1) The final steps in the biosynthesis of rapamycin involve oxidations at C15 and C32 by cytochromes P-450 and three methylations on oxygens at C7, C32, and C41.2) Many of the possible biosynthetic intermediates that lack full elaboration at these positions have been isolated and characterized.3) In the course of evaluating rapamycin producers in our collection of actinomycetes, we encountered a new strain, designated LL-D45042, that makes the previously unreported rapamycin intermediate, 15-deoxo-7,32-Odidesmethylrapamycin (2). We herein report the preliminary characterization of the strain, and the isolation, structure determination and biological activity of the new compound.