The first total synthesis of tubulysin D is reported. The development and application of new tert-butanesulfinamide methods allowed for rapid syntheses of the tubuvaline and tubuphenylalanine fragments. Most significantly, a route was devised and implemented to introduce and carry forward the highly labile N,O-acetal functionality. Tubulysin D is the most active member of the tubulysin family, and the efficient synthetic route described herein will allow for the rapid syntheses of analogues to probe the biological activity of this important class of natural products.

The hypoxia-inducible factor (HIF) prolyl hydroxylase (PHD) enzymes represent novel targets for the treatment of anemia, ulcerative colitis, and ischemic and metabolic disease inter alia. We have identified a novel small-molecule inhibitor of PHD, 1-(5-chloro-6-(trifluoromethoxy)-1H-benzoimidazol-2-yl)-1H-pyrazole-4-carboxylic acid (JNJ-42041935), through structurebased drug design methods. The pharmacology of JNJ-42041935 was investigated in enzyme, cellular, and wholeanimal systems and was compared with other compounds described in the literature as PHD inhibitors. JNJ-42041935, was a potent (pK I ϭ 7.3-7.9), 2-oxoglutarate competitive, reversible, and selective inhibitor of PHD enzymes. In addition, JNJ-42041935 was used to compare the effect of selective inhibition of PHD to intermittent, high doses (50 g/kg i.p.) of an exogenous erythropoietin receptor agonist in an inflammationinduced anemia model in rats. JNJ-42041935 (100 mol/kg, once a day for 14 days) was effective in reversing inflammationinduced anemia, whereas erythropoietin had no effect. The results demonstrate that JNJ-42041935 is a new pharmacological tool, which can be used to investigate PHD inhibition and demonstrate that PHD inhibitors offer great promise for the treatment of inflammation-induced anemia.

HIF prolyl 4-hydroxylases (PHD) are a family of enzymes that mediate key physiological responses to hypoxia by modulating the levels of hypoxia inducible factor 1-R (HIF1R). Certain benzimidazole-2-pyrazole carboxylates were discovered to be PHD2 inhibitors using ligand-and structure-based methods and found to be potent, orally efficacious stimulators of erythropoietin secretion in vivo.

Ten analogues of tubulysin D were synthesized and assayed against established mammalian cell lines, including cancer cells measuring inhibition of cell growth by an MTT assay. These experiments establish for the first time the essential features for the potent cytotoxicity of tubulysin D. The activities of analogues 2 to 5 demonstrate that numerous modifications may be introduced at the C-terminus of the natural product with only modest loss in activity, while the activities of analogues 6 to 8 suggest that a basic amine must be present at the N-terminus to maintain activity. Most surprisingly, analogue 10 establishes that replacement of the chemically labile O-acyl N,O-acetal with the stable N-methyl group results in almost no loss in activity. In aggregate, these structure-activity relationships enable the design of analogues such as 11 that are smaller and considerably more stable than tubulysin D but that maintain most of its potent cell-growth inhibitory activity.

A one-pot method for the asymmetric synthesis of tert-butanesulfinyl-protected amines is described. Condensation of aryl alkyl and dialkyl ketones with tert-butanesulfinamide followed by in situ reduction with the appropriate reagent provides either diastereomer of the sulfinamide products in good yields and with diastereomeric ratios of up to 99:1.