Jadomycins Derived from the Assimilation and Incorporation of Norvaline and Norleucine Stephanie N. Dupuis, † Thomas Veinot, ‡ Susan M. A. Monro, § Susan E. Douglas, ⊥,∥ Raymond T. Syvitski, †,⊥ Kerry B. Goralski, ‡,∇ Sherri A. McFarland, § and David L. Jakeman* ,†,‡ † Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada ‡ College of Pharmacy, Dalhousie University, Halifax, Nova Scotia, Canada § Department of Chemistry, Acadia University, Wolfville, Nova Scotia, Canada ⊥ Institute for Marine Biosciences, National Research Council of Canada, Halifax, Nova Scotia, Canada ∥ Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada ∇ Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada * S Supporting Information ABSTRACT: Streptomyces venezuelae ISP5230 is recognized for the production of chloramphenicol and the jadomycin family of natural products. The jadomycins are angucycline natural products containing a unique oxazolone ring incorporating an amino acid present in the minimal culture media. Substitution of different amino acids results in products of varying biological activity. Analysis of cultures of S. venezuelae ISP5230 incubated with L- and D-norvaline and L- and D-norleucine indicated that only the D-configured amino acids were incorporated into the natural products. Subsequently, jadomycin DNV and jadomycin DNL were isolated and characterized (titers 4 and 9 mg L −1 , respectively). The compounds were evaluated in the National Cancer Institute cell line cancer growth inhibition and cytotoxicity screens, for antimicrobial activity against selected Gram-positive and Gram-negative bacteria, and as DNA-cleavage agents in vitro. P olyketide synthases are multienzyme complexes responsible for the production of numerous bioactive natural products encompassing a broad scope of structural diversity. Many of the compounds produced by polyketide synthases have important roles as clinically approved drugs. 1 Streptomyces venezuelae ISP5230 (Streptomyces venezuelae ATCC 10712) is known to produce chloramphenicol and the jadomycin family of natural products. Analysis of the recently released genome sequence of the organism 2 using antiSMASH 3 resulted in the identification of 26 additional natural product biosynthetic gene clusters, including four additional polyketide synthase clusters. Another biosynthetic cluster was independently described as a novel lantibiotic biosynthetic cluster, although production of the natural product was not accomplished within S. venezuelae or within S. lividans, a heterologous host. 4 This illustrates a significant challenge associated with inducing anticipated cryptic biosynthetic gene clusters identified through genome sequencing. 5 Jadomycins A and B were serendipitously discovered to be induced through phage, heat, or ethanol shock 6,7 when S. venezuelae ISP5230 was cultivated in a minimal media. The jadomycins are members of the angucycline family, which includes the landomycins, 8 urdamycins, 9,10 and kinamy- cins. 10 The polyaromatic backbone of angucyclines is generated through a type II polyketide synthase. 11 The structural diversity observed with products of polyketide synthases is in part due to the variety of mechanisms employed to cyclize the poly-β- ketone backbone. 12,13 In the case of the jadomycins, a unique structural feature is the oxazolone ring and the discovery that it is likely formed in a nonenzymatic fashion (Scheme 1). 14 The nonenzymatic nature of this step is supported by the total synthesis studies of jadomycin A, 15 where condensation of an aldehyde and a carboxyl-protected amino acid proceeded smoothly to form an aldimine that cyclized to furnish a hemiaminal. Upon deprotection of the carboxyl functionality, a second spontaneous cyclization occurred to form the oxazolone ring. The nonenzymatic incorporation of amino acids into the jadomycin oxazolone ring provides an opportunity to explore structure−activity relationships. As part of our structure− function studies on the jadomycins, a number of structurally related oxazolone analogues have been characterized and evaluated. 16−18 Different mechanisms of DNA cleavage have been identified for jadomycin B, jadomycin L, jadomycin G, and jadomycin S-Phe, 19 clearly exemplifying the importance of the substituents around the oxazolone ring in the in vitro DNA cleavage assays. Jadomycin L has been evaluated by the National Cancer Institute (NCI) in its 60-cell-line screening program, 20 and to provide further structure−activity studies, we embarked upon analyzing cultures of S. venezuelae ISP5230 Received: August 19, 2011 Published: November 3, 2011 Article pubs.acs.org/jnp Published 2011 by the American Chemical Society 2420 dx.doi.org/10.1021/np200689w | J. Nat. Prod. 2011, 74, 2420−2424