The discovery of two histamine H(3) antagonist clinical candidates is disclosed. The pathway to identification of the two clinical candidates, 6 (PF-03654746) and 7 (PF-03654764) required five hypothesis driven design cycles. The key to success in identifying these clinical candidates was the development of a compound design strategy that leveraged medicinal chemistry knowledge and traditional assays in conjunction with computational and in vitro safety tools. Overall, clinical compounds 6 and 7 exceeded conservative safety margins and possessed optimal pharmacological and pharmacokinetic profiles, thus achieving our initial goal of identifying compounds with fully aligned oral drug attributes, "best-in-class" molecules.

The multihundred-gram synthesis of [2-(3-methyl-3H-imidazol-4-yl)-thieno[3,2-b]pyridin-7-yl]-(2-methyl-1H-indol-5-yl)-amine (1) is described utilizing a Stille cross-coupling of an iodothienopyridine (3) with 5-(tributylstannyl)-1-methylimidazole (11). Several cross-coupling methods were evaluated for the conversion of thienopyridine 3 to imidazole-thienopyridine 2, but only two were effective: the Stille coupling and a Negishi cross-coupling of the organozinc reagent derived from 2-(tertbutyldimethylsilyl)-1-methylimidazole and iodothienopyridine (3). The latter procedure worked well on laboratory scale (<50 g), but was capricious upon scale-up. The issues with scale-up of an organostannane reagent are discussed, including control and analysis of organotin levels.

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The synthesis of the anti-cancer compound 2-methoxy-N-(3-{4-[3-methyl-4-(6-methyl-pyridin-3-yloxy)phenylamino]quinazolin-6-yl}-E-allyl)acetamide (CP-724,714) (1) on multikilogram scale using several different synthetic routes is described. Application of the Sonogashira, Suzuki, and Heck couplings to this synthesis was investigated to identify a safe, environmentally friendly, and robust process for the production of this drug candidate. A convergent and selective synthesis of the candidate was identified which utilizes a Heck coupling of a protected allylamine to install the critical olefin.

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